View source for Rep:Mod:seaunicorn12

=== A note on accuracy ===
Values in summary tables are quoted to the full number of decimal places as given by Gaussian. Any calculated values are given to fewer decimal places to account for errors and inaccuracy in calculations.
<br>

== Mod 2: Week 1, Day 1 ==
=== Part 2: BH<sub>3</sub> Molecule optimisation 3-21 ===
The BH3 bond lengths were set to 1.5Å as the starting point. <br>
==== Optimisation file ====
[[File:Vm1110_BH3_OPT.LOG]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 3-21G<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -26.46226338 au<br>
'''RMS Gradient Norm''': 0.00020672 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Point Group''': D<sub>3</sub>H<br>
'''Job cpu time''': 39.0 seconds.<br>
<br>
The symmetry assigned to the molecule by Gaussian corresponds to the actual symmetry of the molecule, no symmetry restrictions required for further steps.
<br>
==== Item table ====
<pre> 
        Item               Value     Threshold  Converged?
 Maximum Force            0.000413     0.000450     YES
 RMS     Force            0.000271     0.000300     YES
 Maximum Displacement     0.001610     0.001800     YES
 RMS     Displacement     0.001054     0.001200     YES
 Predicted change in Energy=-1.071764D-06
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  1.1935         -DE/DX =    0.0004              !
 ! R2    R(1,3)                  1.1935         -DE/DX =    0.0004              !
 ! R3    R(1,4)                  1.1935         -DE/DX =    0.0004              !
 ! A1    A(2,1,3)              120.0            -DE/DX =    0.0                 !
 ! A2    A(2,1,4)              120.0            -DE/DX =    0.0                 !
 ! A3    A(3,1,4)              120.0            -DE/DX =    0.0                 !
 ! D1    D(2,1,4,3)            180.0            -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
<br><br>

=== Part 7: BH<sub>3</sub> Molecule optimisation 6-31G(d,p) ===
==== Optimisation file ====
[[File:Vm1110_BH3_OPT2.LOG]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -26.61532252 au<br>
'''RMS Gradient Norm''': 0.00021672 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Point Group''': D<sub>3</sub>H<br>
'''Job cpu time''': 31.0 seconds.<br>
<br>
The B-H bond length in the BH<sub>3</sub> molecule had decreased from the first optimisation from 1.193 to 1.1914 Å. This is a change of 0.02 ± 0.01 Å.
==== Item table ====
<pre> 
         Item               Value     Threshold  Converged?
 Maximum Force            0.000433     0.000450     YES
 RMS     Force            0.000284     0.000300     YES
 Maximum Displacement     0.001702     0.001800     YES
 RMS     Displacement     0.001114     0.001200     YES
 Predicted change in Energy=-1.189019D-06
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  1.1914         -DE/DX =    0.0004              !
 ! R2    R(1,3)                  1.1914         -DE/DX =    0.0004              !
 ! R3    R(1,4)                  1.1914         -DE/DX =    0.0004              !
 ! A1    A(2,1,3)              120.0            -DE/DX =    0.0                 !
 ! A2    A(2,1,4)              120.0            -DE/DX =    0.0                 !
 ! A3    A(3,1,4)              120.0            -DE/DX =    0.0                 !
 ! D1    D(2,1,4,3)            180.0            -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
<br>

== Mod 2: Week 1, Day 2 ==
=== Part 1: TlBr<sub>3</sub> Molecule optimization LanL2DZ ===
The point group was restricted to D3H on very tight (0.0001) tolerance. <br>
{{DOI|10042/21611}}<br>
[[File:Vm1110_TlBr_opt_lanL2DZ.log‎]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': LANL2DZ<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -91.21812851 au<br>
'''RMS Gradient Norm''': 0.00000090 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Point Group''': D<sub>3</sub>H<br>
'''Job cpu time''': 19.2 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000002     0.000450     YES
 RMS     Force            0.000001     0.000300     YES
 Maximum Displacement     0.000022     0.001800     YES
 RMS     Displacement     0.000014     0.001200     YES
 Predicted change in Energy=-6.084147D-11
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  2.651          -DE/DX =    0.0                 !
 ! R2    R(1,3)                  2.651          -DE/DX =    0.0                 !
 ! R3    R(1,4)                  2.651          -DE/DX =    0.0                 !
 ! A1    A(2,1,3)              120.0            -DE/DX =    0.0                 !
 ! A2    A(2,1,4)              120.0            -DE/DX =    0.0                 !
 ! A3    A(3,1,4)              120.0            -DE/DX =    0.0                 !
 ! D1    D(2,1,4,3)            180.0            -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
<br>
'''Optimised bond length''': 2.65 Å (literature: 2.5 Å<ref name="Tl_Br_bond"/>)<br>
'''Optimised Br-Tl-Br bond angle''': 120°<br>
The reported bond length from the optimization is 2.65 ± 0.01 Å which is a little different from the literature value of 6.5 Å<ref name="Tl_Br_bond"/>. The difference in value could be attributed to the bond length being measured in a different molecule. Also, slight disparities between theoretical calculation and experimentally determined values.
<br>
=== Part 2: BBr<sub>3</sub> Molecule optimization [Gen: B(6-31G(d,p); Br(LanL2DZ)] ===
The structure of the BBr<sub>3</sub> molecule was based on the optimized BH<sub>3</sub> molecule with H atoms replaced with Br atoms.
<bt>
{{DOI|10042/21622}}<br>
[[File:vm1110_Bbr3_opt_gen2.log‎]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -64.43645296 au<br>
'''RMS Gradient Norm''': 0.00000383 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Point Group''': D<sub>3</sub>H<br>
'''Job cpu time''': 10.9 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000008     0.000450     YES
 RMS     Force            0.000005     0.000300     YES
 Maximum Displacement     0.000046     0.001800     YES
 RMS     Displacement     0.000030     0.001200     YES
 Predicted change in Energy=-5.266345D-10
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  1.934          -DE/DX =    0.0                 !
 ! R2    R(1,3)                  1.934          -DE/DX =    0.0                 !
 ! R3    R(1,4)                  1.934          -DE/DX =    0.0                 !
 ! A1    A(2,1,3)              120.0            -DE/DX =    0.0                 !
 ! A2    A(2,1,4)              120.0            -DE/DX =    0.0                 !
 ! A3    A(3,1,4)              120.0            -DE/DX =    0.0                 !
 ! D1    D(2,1,4,3)            180.0            -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
<br>
'''Optimised bond length''': 1.934 Å <br>
'''Optimised Br-B-Br bond angle''': 120°<br>
<br>

=== Part 3: Comparing BH3, BBr3 and TlBr3 bond lengths ===
{| class="wikitable" border="1"
|+ Bond lengths
|-
|BH3 || BBr3 || TlBr3
|-
|1.19
|1.93
|2.65
|}
<br>
==== Bond length discussion ====
The central atom-ligand bond increases in the order B-H < B-Br < Tl-Br.
<br>
From the values for the B-H and B-Br bond lengths, certain information can be deduced regarding the effect of changing the ligand has on bond length. The bond length increases from 1.19 Å to 1.93 Å which is a 0.74 ± 0.01 Å increase. H is a much smaller atom then Br (smaller covalent and van der Waal radii) which means that when it bonds, it bonds much closer to the central atom, hence a shorter bond length. Br and H are similar in that they both require 1 electron to fulfill their octet and doublet respectively. They are also both quite electronegative, Br more so than H, which means that their orbitals are not very diffuse and the bond lengths are shorter than would be for less electronegative atoms.
<br>
Comparing the B-Br bond length with the Tl-Br bond length gives the insight on how changing the central atom has on the bond length between central atom and ligand. Boron and Thallium are both in group 13 so they have the same valence electron structure and require the same number of electrons to complete their octet. Boron is slightly more electronegative than Thallium and as such has less diffuse orbitals. However, as Thallium is in group 6 (vs group 2 for Boron) it has many more orbitals and as such this is the largest contributing factor to it's larger size (rather than electronegativity). The increased size of the atom increases the bond length in this case B-Br and Tl-Br bond lengths are 1.93 Å and 2.65 Å respectively and the increase in bond length is 0.72 ± 0.01 Å.
<br>
=== What is a bond? ===
Gaussview does not always draw bonds between atoms within a structure even if the bonds exist. Gaussview draws in bonds below a pre-defined value for the particular bond in question. For example, in the optimisation of BH3, a bond length of 1.4 Å is not drawn as a visible bond but a bond of 1.2 Å is. This does not mean that there is no bond, Gaussview assigns bonds according to the distance between atoms rather than bonding or non bonding character of the molecular orbitals.
<bt>
A bond can be defined in one way as the existence of electrons in molecular orbitals of lower energy than the atomic orbitals, with a largely bonding character. In that way if there are equally as many electrons in antibonding orbitals as there are in bonding orbitals, a bond will not form because the molecule is not stabilized. In addition, any electrons residing in non-bonding orbitals do not contribute to the overall bond.

== Mod 2: Day 3 ==
=== Part 2: BH3 Molecule frequency ===
[[File:VM1110_BH3_FREQ.LOG]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -26.61532252 au<br>
'''RMS Gradient Norm''': 0.00021669 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Point Group''': D3H<br>
'''Job cpu time''': 8.0 seconds.<br>
<pre>
 Low frequencies ---  -70.3431  -69.5542  -69.5540   -0.0055    0.0695    0.1595
 Low frequencies --- 1161.4019 1212.1084 1212.1111
</pre>
The low frequencies do not fall into the ±15 range however there are no negative vibrational modes which indicates that the molecule was in fact optimized to a minimum. The large range for the low frequencies may be in part due to the basis set used or the symmetry of the molecule. As it is a very small molecule it is possible to have lower accuracy and therefore larger errors.
<br>

=== Part 3: BH3 Molecule vibrations ===
{| class="wikitable" border="1"
|+ BH3 molecule vibrations
|-
|no. || Form of the vibration || Frequency || Intensity || symmetry D3H point group 
|-
|1
|[[File:vm1110_BH3_vib_1.gif|250px]] <br>The H atoms move in and out of the plane of the molecule in a concerted motion. The B atom moves in and out of the plane of the molecule in the opposite direction of the H atoms and isn't displaced as far. 
|1161.40
|92.7103
|A2"
|-
|2
|[[File:vm1110_BH3_vib_2.gif|250px]] <br>Two H atoms move sideways towards one another in a concerted motion. The remaining H atom and the B atom move very slightly together, in and out, away from the two H atoms.
|1212.11
|13.9813
|E'
|-
|3
|[[File:vm1110_BH3_vib_3.gif|250px]] <br>Two of the H atoms bend around the central B atom in a concerted motion. The third H atom also stretches around the central B atom but with a greater overall displacement and in a clockwise direction rather than the anticlockwise direction of the other two atoms. The B atom moves very slightly in the opposite direction of the third H atom.
|1212.11
|13.9849
|E'
|-
|4
|[[File:vm1110_BH3_vib_4.gif|250px]] <br>The H atoms move in and out from the B atom in a concerted motion. The B atom remains motionless. All stretching is done in the plane of the molecule.
|2587.81
|0
|A1'
|-
|5
|[[File:vm1110_BH3_vib_5.gif|250px]] <br> Two of the H atoms are moving in and out from the B atom, in the plane of the molecule, but in an asymmetric manner (while one stretches out, the other stretches in). The third H atom remains fixed. The B atoms moves very slightly in the direction of the H atom coming towards it.
|2721.52
|126.1376
|E'
|-
|6
|[[File:vm1110_BH3_vib_6.gif|250px]] <br> All the H atoms move in and out from the B atom, in the plane of the molecule. Two of the H atoms move in a concerted manner and the third moved in the opposite direction. The B atoms moves very slightly towards the H atoms nearest to it.
|2721.52
|126.1280
|E'
|}
<br>
==== IR spectrum ====
[[File:vm1110_BH3_freq_ir_spectrum.png|700px]]
<br>
Only 3 peaks are visible in the IR spectrum. This is because vibrations 5 and 6 and, 2 and 3 have the same frequency and therefore show up as a single peak. In addition, vibration 4 has an intensity of 0, hence it has no peak on the spectrum.

=== Part 4: TlBr<sub>3</sub> Molecule frequency ===
{{DOI|10042/22056}}<br>
[[File:Vm1110_TlBr_opt_lanL2DZ_freq.log‎]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': LANL2DZ<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -91.21812851 au<br>
'''RMS Gradient Norm''': 0.00000088 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Point Group''': D<sub>3</sub>H<br>
'''Job cpu time''': 22.0 seconds.<br>
<pre>
  Low frequencies ---   -3.4213   -0.0026   -0.0004    0.0015    3.9367    3.9367
  Low frequencies ---   46.4289   46.4292   52.1449
</pre>
'''Lowest frequency mode''': 46.4289 (E')
<br>
==== Ir Spectrum ====
[[File:vm1110_TlBr3_freq_ir_spectrum.png|700px]]
==== Vibrational frequency comparison ====
{| class="wikitable" border="1"
|-
! rowspan="2" |Number
! colspan="2" | Boron
! colspan="2" | Thallium
|-
!Frequency
!Symmetry
!Frequency
!Symmetry
|-
|1
|1161.40
|A2"
|46.4289
|E'
|-
|2
|1212.11
|E'
|46.4292
|E'
|-
|3
|1212.11
|E'
|52.1449
|A2"
|-
|4
|2587.81
|A1'
|165.2685
|A1'
|-
|5
|2721.52
|E'
|210.6948
|E'
|-
|6
|2721.52
|E'
|210.6948
|E'
|}
<br>
By comparison it is possible to see that the frequencies for TlBr<sub>3</sub> are much lower than for BH<sub>3</sub>. This shows that the Tl-Br bonds are much weaker than B-H bonds. In addition to the vast difference in frequencies, there has also been a reordering of the modes. Where as in BH<sub>3</sub> the lowest frequency mode was A2" in TlBr3 the lowest frequency mode is E' symmetry and the A2" mode is of the third lowest frequency. <br>
The two spectra are similar in the manner that the both have two peaks at a lower frequency and one large peak at the highest frequency. The peaks on the thallium spectrum are much broader and far less intense. Also there is more of an overlap of the two peaks in the lower frequency region leading to a more spread double pointed peak rather than two distinct peaks. The A1' and E' vibrations lie at a higher frequency for both spectra because they are of a higher energy than the A2" and E' vibrations.
<br>
==== Frequency calculations ====
Frequency calculations are run using the same basis set as the optimizations because these determine the symmetry of the molecule and the way in which the energy is measured. The lowest energy version of a molecule in one basis set might not be the lowest energy conformation in another basis set. Hence for the frequency analysis to work the energy must be at a minimum and the basis set must be the same. <br>
The frequency analysis gives information regarding the vibrations of the molecule at its lowest energy state. This information can be used to find which vibrations are IR active and hence create a theoretical IR spectrum. <br>
The 6 low frequencies are the motion of the molecule's centre of mass. When these values are low it means the molecule has been fully optimized and the frequency analysis is not affected by the motion of the overall molecule in measuring the molecule's vibrations.
=== Part 5: BH<sub>3</sub> Molecular Orbitals ===
{{DOI|10042/22065}}<br>
[[File:vm1110_BH3_MOs.fchk‎]]<br>
'''File Type''': .fch<br>
'''Calculation Type''': SP<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -26.53393782 au<br>
'''RMS Gradient Norm''': 0.00000000 au<br>
'''Dipole Moment''': 0.0000 Debye<br>
'''Job cpu time''': 0.9 seconds.<br>
{| class="wikitable" border="1"
|-
!Molecular orbital Diagram
!Calculated molecular orbitals
|-
| rowspan="4" | [[File:vm1110_BH3_mo_diagram.png|500px]]
|[[File:vm1110_BH3_mo_5.png|150px]]<br>LUMO (a2")
|-
|[[File:vm1110_BH3_mo_4.png|150px]]<br> (e')
|-
|[[File:vm1110_BH3_mo_3.png|150px]]<br> (e')
|-
|[[File:vm1110_BH3_mo_2.png|150px]]<br> (a1')
|}
==== Discussion ====
The LCAO orbitals and the calculated orbitals are all quite similar in appearance, the calculated orbitals more combined to give one overall orbital rather rather than distinct overlapped orbitals. However they are still quite similar. This shows that in this case LCAO theory works well to define what is observed through calculation.

== Mod 2: Day 4 ==
=== Part 1: NBO Analysis ===
=== NH<sub>3</sub> optimisation ===
{{DOI|10042/22066}}<br>
[[File:VM1110_NH3_OPT_631_GDP_2.log‎]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -56.55776856 au<br>
'''RMS Gradient Norm''': 0.00000888 au<br>
'''Dipole Moment''': 1.8464 Debye<br>
'''Point Group''': C1<br>
'''Job cpu time''': 8.7 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000024     0.000450     YES
 RMS     Force            0.000012     0.000300     YES
 Maximum Displacement     0.000088     0.001800     YES
 RMS     Displacement     0.000056     0.001200     YES
 Predicted change in Energy=-1.759459D-09
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  1.018          -DE/DX =    0.0                 !
 ! R2    R(1,3)                  1.018          -DE/DX =    0.0                 !
 ! R3    R(1,4)                  1.018          -DE/DX =    0.0                 !
 ! A1    A(2,1,3)              105.7414         -DE/DX =    0.0                 !
 ! A2    A(2,1,4)              105.7486         -DE/DX =    0.0                 !
 ! A3    A(3,1,4)              105.7478         -DE/DX =    0.0                 !
 ! D1    D(2,1,4,3)           -111.8631         -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
=== NH<sub>3</sub> frequency calculation ===
{{DOI|10042/22067}}<br>
[[File:VM1110_NH3_freq.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -56.55776856 au<br>
'''RMS Gradient Norm''': 0.00000888 au<br>
'''Dipole Moment''': 1.8464 Debye<br>
'''Point Group''': C1<br>
'''Job cpu time''': 17.0 seconds.<br>
<pre>
 Low frequencies ---  -30.7764   -0.0020   -0.0018   -0.0012   20.3142   28.2484
 Low frequencies --- 1089.5557 1694.1237 1694.1868
</pre>
=== NH<sub>3</sub> population analysis ===
[[File:VM1110_NH3_pop.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': SP<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -56.55776856 au<br>
'''RMS Gradient Norm''':  au<br>
'''Dipole Moment''': 1.8464 Debye<br>
'''Point Group''': C1<br>
'''Job cpu time''': 15.8 seconds.<br>
=== NH<sub>3</sub> NBO analysis ===
{| class="wikitable" border="1"
|-
!colspan="2" | NH3 charge distribution (-1.0 to +1.0)
|-
|colspan="2" |[[File:vm1110_NH3_pop_nbo_charge.png|300px]]
|-
!N Charge
!H Charge
|-
| -1.125
| 0.375
|}
<br>
=== Part 2: Association energy ===

=== NH<sub>3</sub>BH<sub>3</sub> optimisation ===
{{DOI|10042/}}<br>
[[File:VM1110_NH3BH3_opt_631_gdp_2.log‎‎]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -83.22468730 au<br>
'''RMS Gradient Norm''': 0.00005971 au<br>
'''Dipole Moment''': 5.5649 Debye<br>
'''Point Group''': C1<br>
'''Job cpu time''': 16.8 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000122     0.000450     YES
 RMS     Force            0.000057     0.000300     YES
 Maximum Displacement     0.000662     0.001800     YES
 RMS     Displacement     0.000295     0.001200     YES
 Predicted change in Energy=-1.639776D-07
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,8)                  1.21           -DE/DX =   -0.0001              !
 ! R2    R(2,8)                  1.2101         -DE/DX =   -0.0001              !
 ! R3    R(3,8)                  1.2101         -DE/DX =   -0.0001              !
 ! R4    R(4,7)                  1.0186         -DE/DX =   -0.0001              !
 ! R5    R(5,7)                  1.0186         -DE/DX =   -0.0001              !
 ! R6    R(6,7)                  1.0186         -DE/DX =   -0.0001              !
 ! R7    R(7,8)                  1.6681         -DE/DX =   -0.0001              !
 ! A1    A(4,7,5)              107.8722         -DE/DX =    0.0                 !
 ! A2    A(4,7,6)              107.8744         -DE/DX =    0.0                 !
 ! A3    A(4,7,8)              111.0188         -DE/DX =    0.0                 !
 ! A4    A(5,7,6)              107.8673         -DE/DX =    0.0                 !
 ! A5    A(5,7,8)              111.0335         -DE/DX =    0.0                 !
 ! A6    A(6,7,8)              111.0296         -DE/DX =    0.0                 !
 ! A7    A(1,8,2)              113.8814         -DE/DX =    0.0                 !
 ! A8    A(1,8,3)              113.879          -DE/DX =    0.0                 !
 ! A9    A(1,8,7)              104.5977         -DE/DX =    0.0                 !
 ! A10   A(2,8,3)              113.8671         -DE/DX =    0.0                 !
 ! A11   A(2,8,7)              104.5945         -DE/DX =    0.0                 !
 ! A12   A(3,8,7)              104.5926         -DE/DX =    0.0                 !
 ! D1    D(4,7,8,1)            179.9734         -DE/DX =    0.0                 !
 ! D2    D(4,7,8,2)            -60.0193         -DE/DX =    0.0                 !
 ! D3    D(4,7,8,3)             59.9696         -DE/DX =    0.0                 !
 ! D4    D(5,7,8,1)            -60.027          -DE/DX =    0.0                 !
 ! D5    D(5,7,8,2)             59.9803         -DE/DX =    0.0                 !
 ! D6    D(5,7,8,3)            179.9692         -DE/DX =    0.0                 !
 ! D7    D(6,7,8,1)             59.9736         -DE/DX =    0.0                 !
 ! D8    D(6,7,8,2)            179.9809         -DE/DX =    0.0                 !
 ! D9    D(6,7,8,3)            -60.0302         -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>

=== NH<sub>3</sub>BH<sub>3</sub> frequency ===
{{DOI|10042/}}<br>
[[File:VM1110_NH3BH3_freq_2.log‎]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': 6-31G(d,p)<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -83.22468730 au<br>
'''RMS Gradient Norm''': 0.00005971 au<br>
'''Dipole Moment''': 5.5649 Debye<br>
'''Point Group''': C1<br>
'''Job cpu time''': 1 minute 8.9 seconds.<br>
<pre>
 Low frequencies ---  -13.5525   -0.0010   -0.0008   -0.0006   16.5718   28.9370
 Low frequencies ---  265.0672  632.1225  638.0187
</pre>
=== Energy comparison ===
{| class="wikitable" border="1"
|-
! Molecule
! Energy
|-
| NH3
| -56.55776856 au
|-
| BH3
| -26.61532252 au
|-
| NH3BH3
| -83.22468730 au
|-
|ΔE
| -0.052 au (-135.47kJ/mol)
|}
'''Dissociation energy''': -135.47 kJ/mol

== Mod 2: Week 2, AlCl<sub>2</sub>Br dimer isomers ==
=== Part 1: AlCl<sub>2</sub>Br dimer optimisations ===
==== Isomer 1 ====
[[File:vm1110_Isomer_1.png|200px]]<br>
[[File:vm1110_AlCl4Br2_isomer_1_opt_gen_3.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.40630797 au<br>
'''RMS Gradient Norm''': 0.00000327 au<br>
'''Dipole Moment''': 0.0012 Debye<br>
'''Point Group''': C2V<br>
'''Job cpu time''': 28.4 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000008     0.000450     YES
 RMS     Force            0.000004     0.000300     YES
 Maximum Displacement     0.000324     0.001800     YES
 RMS     Displacement     0.000097     0.001200     YES
 Predicted change in Energy=-1.843622D-09
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,8)                  2.0934         -DE/DX =    0.0                 !
 ! R2    R(2,8)                  2.0934         -DE/DX =    0.0                 !
 ! R3    R(3,7)                  2.0934         -DE/DX =    0.0                 !
 ! R4    R(4,7)                  2.0934         -DE/DX =    0.0                 !
 ! R5    R(5,7)                  2.4893         -DE/DX =    0.0                 !
 ! R6    R(5,8)                  2.4893         -DE/DX =    0.0                 !
 ! R7    R(6,7)                  2.4893         -DE/DX =    0.0                 !
 ! R8    R(6,8)                  2.4893         -DE/DX =    0.0                 !
 ! A1    A(7,5,8)               88.2675         -DE/DX =    0.0                 !
 ! A2    A(7,6,8)               88.2675         -DE/DX =    0.0                 !
 ! A3    A(3,7,4)              121.7613         -DE/DX =    0.0                 !
 ! A4    A(3,7,5)              109.8017         -DE/DX =    0.0                 !
 ! A5    A(3,7,6)              109.8017         -DE/DX =    0.0                 !
 ! A6    A(4,7,5)              109.813          -DE/DX =    0.0                 !
 ! A7    A(4,7,6)              109.813          -DE/DX =    0.0                 !
 ! A8    A(5,7,6)               91.7325         -DE/DX =    0.0                 !
 ! A9    A(1,8,2)              121.7613         -DE/DX =    0.0                 !
 ! A10   A(1,8,5)              109.8017         -DE/DX =    0.0                 !
 ! A11   A(1,8,6)              109.8017         -DE/DX =    0.0                 !
 ! A12   A(2,8,5)              109.813          -DE/DX =    0.0                 !
 ! A13   A(2,8,6)              109.813          -DE/DX =    0.0                 !
 ! A14   A(5,8,6)               91.7325         -DE/DX =    0.0                 !
 ! D1    D(8,5,7,3)           -111.7781         -DE/DX =    0.0                 !
 ! D2    D(8,5,7,4)            111.8043         -DE/DX =    0.0                 !
 ! D3    D(8,5,7,6)              0.006          -DE/DX =    0.0                 !
 ! D4    D(7,5,8,1)            111.7781         -DE/DX =    0.0                 !
 ! D5    D(7,5,8,2)           -111.8043         -DE/DX =    0.0                 !
 ! D6    D(7,5,8,6)             -0.006          -DE/DX =    0.0                 !
 ! D7    D(8,6,7,3)            111.7781         -DE/DX =    0.0                 !
 ! D8    D(8,6,7,4)           -111.8043         -DE/DX =    0.0                 !
 ! D9    D(8,6,7,5)             -0.006          -DE/DX =    0.0                 !
 ! D10   D(7,6,8,1)           -111.7781         -DE/DX =    0.0                 !
 ! D11   D(7,6,8,2)            111.8043         -DE/DX =    0.0                 !
 ! D12   D(7,6,8,5)              0.006          -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>


==== Isomer 2 ====
[[File:vm1110_Isomer_2.png|200px]]<br>
[[File:vm1110_AlCl4Br2_isomer_3_opt_gen_3.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41632880 au<br>
'''RMS Gradient Norm''': 0.00002607 au<br>
'''Dipole Moment''': 0.1920 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': 54.9 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000083     0.000450     YES
 RMS     Force            0.000031     0.000300     YES
 Maximum Displacement     0.000571     0.001800     YES
 RMS     Displacement     0.000264     0.001200     YES
 Predicted change in Energy=-6.679677D-08
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,3)                  2.0926         -DE/DX =    0.0                 !
 ! R2    R(2,3)                  2.0926         -DE/DX =    0.0                 !
 ! R3    R(3,6)                  2.2958         -DE/DX =    0.0                 !
 ! R4    R(3,7)                  2.2958         -DE/DX =    0.0                 !
 ! R5    R(4,5)                  2.2765         -DE/DX =    0.0                 !
 ! R6    R(4,6)                  2.3006         -DE/DX =    0.0                 !
 ! R7    R(4,7)                  2.3006         -DE/DX =    0.0                 !
 ! R8    R(4,8)                  2.2765         -DE/DX =    0.0                 !
 ! A1    A(1,3,2)              121.7655         -DE/DX =    0.0                 !
 ! A2    A(1,3,6)              110.0697         -DE/DX =    0.0                 !
 ! A3    A(1,3,7)              110.0697         -DE/DX =    0.0                 !
 ! A4    A(2,3,6)              110.0696         -DE/DX =    0.0                 !
 ! A5    A(2,3,7)              110.0696         -DE/DX =    0.0                 !
 ! A6    A(6,3,7)               90.3043         -DE/DX =   -0.0001              !
 ! A7    A(5,4,6)              110.2008         -DE/DX =    0.0                 !
 ! A8    A(5,4,7)              110.2008         -DE/DX =    0.0                 !
 ! A9    A(5,4,8)              121.5012         -DE/DX =    0.0                 !
 ! A10   A(6,4,7)               90.0628         -DE/DX =   -0.0001              !
 ! A11   A(6,4,8)              110.2008         -DE/DX =    0.0                 !
 ! A12   A(7,4,8)              110.2008         -DE/DX =    0.0                 !
 ! A13   A(3,6,4)               89.8164         -DE/DX =    0.0001              !
 ! A14   A(3,7,4)               89.8164         -DE/DX =    0.0001              !
 ! D1    D(1,3,6,4)           -111.5487         -DE/DX =    0.0                 !
 ! D2    D(2,3,6,4)            111.5488         -DE/DX =    0.0                 !
 ! D3    D(7,3,6,4)              0.0001         -DE/DX =    0.0                 !
 ! D4    D(1,3,7,4)            111.5487         -DE/DX =    0.0                 !
 ! D5    D(2,3,7,4)           -111.5488         -DE/DX =    0.0                 !
 ! D6    D(6,3,7,4)             -0.0001         -DE/DX =    0.0                 !
 ! D7    D(5,4,6,3)            111.6137         -DE/DX =    0.0                 !
 ! D8    D(7,4,6,3)             -0.0001         -DE/DX =    0.0                 !
 ! D9    D(8,4,6,3)           -111.6138         -DE/DX =    0.0                 !
 ! D10   D(5,4,7,3)           -111.6137         -DE/DX =    0.0                 !
 ! D11   D(6,4,7,3)              0.0001         -DE/DX =    0.0                 !
 ! D12   D(8,4,7,3)            111.6138         -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
==== Isomer 3 ====
[[File:vm1110_Isomer_3.png|200px]]<br>
[[File:vm1110_AlCl4Br2_isomer_4_opt_gen_2.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41626675 au<br>
'''RMS Gradient Norm''': 0.00002016 au<br>
'''Dipole Moment''': 0.1669 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': 52.6 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000049     0.000450     YES
 RMS     Force            0.000020     0.000300     YES
 Maximum Displacement     0.000512     0.001800     YES
 RMS     Displacement     0.000174     0.001200     YES
 Predicted change in Energy=-2.899010D-08
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  2.0939         -DE/DX =    0.0                 !
 ! R2    R(2,5)                  2.2981         -DE/DX =    0.0                 !
 ! R3    R(2,6)                  2.2981         -DE/DX =    0.0                 !
 ! R4    R(2,7)                  2.2747         -DE/DX =    0.0                 !
 ! R5    R(3,4)                  2.2747         -DE/DX =    0.0                 !
 ! R6    R(3,5)                  2.2981         -DE/DX =    0.0                 !
 ! R7    R(3,6)                  2.2981         -DE/DX =    0.0                 !
 ! R8    R(3,8)                  2.0937         -DE/DX =    0.0                 !
 ! A1    A(1,2,5)              109.8477         -DE/DX =    0.0                 !
 ! A2    A(1,2,6)              109.8477         -DE/DX =    0.0                 !
 ! A3    A(1,2,7)              121.4998         -DE/DX =    0.0                 !
 ! A4    A(5,2,6)               90.1702         -DE/DX =    0.0                 !
 ! A5    A(5,2,7)              110.5144         -DE/DX =    0.0                 !
 ! A6    A(6,2,7)              110.5144         -DE/DX =    0.0                 !
 ! A7    A(4,3,5)              110.5164         -DE/DX =    0.0                 !
 ! A8    A(4,3,6)              110.5164         -DE/DX =    0.0                 !
 ! A9    A(4,3,8)              121.4893         -DE/DX =    0.0                 !
 ! A10   A(5,3,6)               90.1678         -DE/DX =    0.0                 !
 ! A11   A(5,3,8)              109.8534         -DE/DX =    0.0                 !
 ! A12   A(6,3,8)              109.8534         -DE/DX =    0.0                 !
 ! A13   A(2,5,3)               89.829          -DE/DX =    0.0                 !
 ! A14   A(2,6,3)               89.829          -DE/DX =    0.0                 !
 ! D1    D(1,2,5,3)            110.7482         -DE/DX =    0.0                 !
 ! D2    D(6,2,5,3)             -0.4771         -DE/DX =    0.0                 !
 ! D3    D(7,2,5,3)           -112.519          -DE/DX =    0.0                 !
 ! D4    D(1,2,6,3)           -110.7482         -DE/DX =    0.0                 !
 ! D5    D(5,2,6,3)              0.4771         -DE/DX =    0.0                 !
 ! D6    D(7,2,6,3)            112.519          -DE/DX =    0.0                 !
 ! D7    D(4,3,5,2)            112.5206         -DE/DX =    0.0                 !
 ! D8    D(6,3,5,2)              0.4771         -DE/DX =    0.0                 !
 ! D9    D(8,3,5,2)           -110.7542         -DE/DX =    0.0                 !
 ! D10   D(4,3,6,2)           -112.5206         -DE/DX =    0.0                 !
 ! D11   D(5,3,6,2)             -0.4771         -DE/DX =    0.0                 !
 ! D12   D(8,3,6,2)            110.7542         -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
==== Isomer 4 ====
[[File:vm1110_Isomer_4.png|200px]]<br>
[[File:vm1110_AlCl4Br2_isomer_5_opt_gen_2.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41631606 au<br>
'''RMS Gradient Norm''': 0.00001798 au<br>
'''Dipole Moment''': 0.0059 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': 54.8 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000046     0.000450     YES
 RMS     Force            0.000017     0.000300     YES
 Maximum Displacement     0.000619     0.001800     YES
 RMS     Displacement     0.000158     0.001200     YES
 Predicted change in Energy=-2.701528D-08
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,4)                  2.2984         -DE/DX =    0.0                 !
 ! R2    R(1,5)                  2.2984         -DE/DX =    0.0                 !
 ! R3    R(1,7)                  2.0938         -DE/DX =    0.0                 !
 ! R4    R(1,8)                  2.2746         -DE/DX =    0.0                 !
 ! R5    R(2,3)                  2.2746         -DE/DX =    0.0                 !
 ! R6    R(2,4)                  2.2985         -DE/DX =    0.0                 !
 ! R7    R(2,5)                  2.2985         -DE/DX =    0.0                 !
 ! R8    R(2,6)                  2.0937         -DE/DX =    0.0                 !
 ! A1    A(4,1,5)               90.1599         -DE/DX =    0.0                 !
 ! A2    A(4,1,7)              109.8678         -DE/DX =    0.0                 !
 ! A3    A(4,1,8)              110.5187         -DE/DX =    0.0                 !
 ! A4    A(5,1,7)              109.8678         -DE/DX =    0.0                 !
 ! A5    A(5,1,8)              110.5187         -DE/DX =    0.0                 !
 ! A6    A(7,1,8)              121.4683         -DE/DX =    0.0                 !
 ! A7    A(3,2,4)              110.4933         -DE/DX =    0.0                 !
 ! A8    A(3,2,5)              110.4933         -DE/DX =    0.0                 !
 ! A9    A(3,2,6)              121.5473         -DE/DX =    0.0                 !
 ! A10   A(4,2,5)               90.1547         -DE/DX =    0.0                 !
 ! A11   A(4,2,6)              109.8433         -DE/DX =    0.0                 !
 ! A12   A(5,2,6)              109.8433         -DE/DX =    0.0                 !
 ! A13   A(1,4,2)               89.8427         -DE/DX =    0.0                 !
 ! A14   A(1,5,2)               89.8427         -DE/DX =    0.0                 !
 ! D1    D(5,1,4,2)             -0.0017         -DE/DX =    0.0                 !
 ! D2    D(7,1,4,2)           -111.2475         -DE/DX =    0.0                 !
 ! D3    D(8,1,4,2)            112.0414         -DE/DX =    0.0                 !
 ! D4    D(4,1,5,2)              0.0017         -DE/DX =    0.0                 !
 ! D5    D(7,1,5,2)            111.2475         -DE/DX =    0.0                 !
 ! D6    D(8,1,5,2)           -112.0414         -DE/DX =    0.0                 !
 ! D7    D(3,2,4,1)            112.0113         -DE/DX =    0.0                 !
 ! D8    D(5,2,4,1)              0.0017         -DE/DX =    0.0                 !
 ! D9    D(6,2,4,1)           -111.2123         -DE/DX =    0.0                 !
 ! D10   D(3,2,5,1)           -112.0113         -DE/DX =    0.0                 !
 ! D11   D(4,2,5,1)             -0.0017         -DE/DX =    0.0                 !
 ! D12   D(6,2,5,1)            111.2123         -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
=== AlCl<sub>2</sub>Br dimer energy differences ===
{| class="wikitable" border="1"
|+ Energies relative to isomer 2
|-
! Isomer
! Energy (au)
! ΔE (au)
! ΔE (kJ/mol)
|-
| 1
| -2352.40630797
| 0.0100
| 26.26
|-
| 2
| -2352.41632880
| 0
| 0
|-
| 3
| -2352.41626675
| 0.0001
| 0.26
|-
| 4
| -2352.41631606
| 0.00001
| 0.02
|}
==== Discussion ====
The isomer of lowest energy is isomer 2 and the isomer of highest energy is isomer 1. Isomer 1 has 2 bridging Br atoms whereas isomers 2, 3 and, 4 have bridging Cl atoms. Hence the dimer is most stable with bridging Cl atoms rather than Br. Isomer 2 has both the terminal Br atoms on one side. Isomers 3 and 4 have the terminal Br atoms on opposite ends in cis and trans conformations respectively. The trans isomer is slightly lower in energy than the cis isomer and both are relatively similar in energy to isomer 2. Hence the molecule is most stable when the Br atoms are terminal and on the same end of the dimer.
==== Momomer optimization ====
[[File:vm1110_AlCl2Br_monomer_opt_gen_3.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FOPT<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -1176.19013667 au<br>
'''RMS Gradient Norm''': 0.00013439 au<br>
'''Dipole Moment''': 0.1194 Debye<br>
'''Point Group''': C2V<br>
'''Job cpu time''': 9.5 seconds.<br>
<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000181     0.000450     YES
 RMS     Force            0.000118     0.000300     YES
 Maximum Displacement     0.001031     0.001800     YES
 RMS     Displacement     0.000577     0.001200     YES
 Predicted change in Energy=-2.606668D-07
 Optimization completed.
    -- Stationary point found.
                           ----------------------------
                           !   Optimized Parameters   !
                           ! (Angstroms and Degrees)  !
 --------------------------                            --------------------------
 ! Name  Definition              Value          Derivative Info.                !
 --------------------------------------------------------------------------------
 ! R1    R(1,2)                  2.27           -DE/DX =   -0.0002              !
 ! R2    R(1,3)                  2.0883         -DE/DX =    0.0002              !
 ! R3    R(1,4)                  2.0883         -DE/DX =    0.0002              !
 ! A1    A(2,1,3)              120.0373         -DE/DX =    0.0                 !
 ! A2    A(2,1,4)              120.0373         -DE/DX =    0.0                 !
 ! A3    A(3,1,4)              119.9254         -DE/DX =    0.0                 !
 ! D1    D(2,1,4,3)            180.0            -DE/DX =    0.0                 !
 --------------------------------------------------------------------------------
 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
</pre>
==== Dimer dissociation energy ====
{| class="wikitable" border="1"
|+ Energies relative to isomer 2
|-
! Molecule
! Energy (au)
! Energy (kJ/mol)
|-
| monomer
| -1176.19013667
| -
|-
| dimer
| -2352.41632880
| -
|-
| ΔE
| -1176.226
| -3.088 10<sup>6</sup>
|}
==== Discussion ====
Isomer 2 of the dimers is much more stable than the monomer on its own. This is shown by the very large dissociation energy.

=== Part 2: AlCl<sub>2</sub>Br dimer frequencies ===
==== Isomer 1 ====
{{DOI|10042/}}<br>
[[File:vm1110_AlCl4Br2_isomer_1_freq.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.40630797 au<br>
'''RMS Gradient Norm''': 0.00000327 au<br>
'''Dipole Moment''': 0.0012 Debye<br>
'''Point Group''': C2V<br>
'''Job cpu time''': 2minutes 1.7 seconds.<br>
<pre>
 Low frequencies ---   -5.1814   -4.9633   -3.1838    0.0030    0.0038    0.0039
 Low frequencies ---   14.8246   63.2887   86.0876
</pre>
{| class="wikitable" border="1"
|+ IR spectrum
|-
|[[File:vm1110_AlCl4Br2_isomer_1_IR.png|300px]]
|}
==== Isomer 2 ====
{{DOI|10042/}}<br>
[[File:vm1110_AlCl4Br2_isomer_3_freq.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41632880 au<br>
'''RMS Gradient Norm''': 0.00002607 au<br>
'''Dipole Moment''': 0.1920 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': 3 minutes 46.9 seconds.<br>
<pre>
 Low frequencies ---   -3.5964   -2.5820   -1.4168   -0.0020    0.0011    0.0027
 Low frequencies ---   17.7720   51.0000   72.1620
</pre>
{| class="wikitable" border="1"
|+ IR spectrum
|-
|[[File:vm1110_AlCl4Br2_isomer_2_IR.png|300px]]
|}
==== Isomer 3 ====
{{DOI|10042/}}<br>
[[File:vm1110_AlCl4Br2_isomer_4_freq.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41626675 au<br>
'''RMS Gradient Norm''': 0.00002016 au<br>
'''Dipole Moment''': 0.1669 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': 3 minutes 11.8 seconds.<br>
<pre>
 Low frequencies ---   -4.0622   -2.3951   -0.0038   -0.0035   -0.0022    1.0273
 Low frequencies ---   17.1580   50.9238   78.5379
</pre>
{| class="wikitable" border="1"
|+ IR spectrum
|-
|[[File:vm1110_AlCl4Br2_isomer_3_IR.png|300px]]
|}
==== Isomer 4 ====
{{DOI|10042/}}<br>
[[File:vm1110_AlCl4Br2_isomer_5_freq.log]]<br>
'''File Type''': .log<br>
'''Calculation Type''': FREQ<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41631606 au<br>
'''RMS Gradient Norm''': 0.00001798 au<br>
'''Dipole Moment''': 0.0059 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': 3 minutes 40.1 seconds.<br>
<pre>
 Low frequencies ---   -0.0013    0.0020    0.0021    2.1254    2.5567    4.1893
 Low frequencies ---   18.1395   49.0727   72.9198
</pre>
{| class="wikitable" border="1"
|+ IR spectrum
|-
|[[File:vm1110_AlCl4Br2_isomer_4_IR.png|300px]]
|}
==== IR spectra discussion ====
More intense bands appear in the spectrum for isomer 1 because more vibrations change the overall dipole of the molecule. In isomers 1 and 2 the Br atoms are close to one another which means that with every vibration there is more electron density moving, leading to more, intense vibrations which show up as a greater number of intense peaks on the IR spectra. Isomer 1 has 18 vibrations and 10 of those are IR inactive. However, of the ones that are IR active, 4 are of a high intensity. The other three isomers have intense IR peaks at approx. 420 which are more intense than any of the isomer 1 peaks but rather than 4, they only have 3 peaks of the same level of intensity. This means that isomer 1 has more vibrations that make a significant change in the overall dipole of the molecule and isomers 3 and 4 have the fewest.
==== IR discussion ====
For a vibration to be IR active it needs to create a change in the overall dipole of the molecule. All vibrations that do not create a change are then IR inactive and show an intensity of 0.
==== Al-Br bond stretch discussion ====
{| class="wikitable" border="1"
|+ Energies relative to isomer 2
|-
! rowspan="2" | Molcule
! colspan="3" | Vibrations
|-
! Frequency
! Images
! Description
|-
! rowspan="6" |Isomer 1
| 196.90
| 0.0
| Al sideways movemenmt in opposite directions, slight Br movement.
|-
| 241.00
| 99.7720
| Al opposite  movement towards and from Br.
|-
| 246.75
| 0.0
| Al concerted inward movement.
|-
| 341.32
| 160.6510
| Al concerted sideways movement.
|-
| 467.22
| 346.5254
| Al opposite movement towards and from Br, Cl outward stretch.
|-
| 493.90
| 0.0
| Al inward movement, Cl outward movement, Br fixed.
|-
! rowspan="5" |Isomer 1
| 186.76
| 1.5858
| Al concerted inwards movemenmt, Br movement toward Al.
|-
| 270.68
| 13.3495
| Al movement outwards in opposite directions, Br moment towards Al.
|-
| 418.55
| 309.6868
| Al between Br atoms outward movement, other atoms relatively fixed.
|-
| 495.50
| 133.7192
| Al between Br atoms sideways movement, other atoms relatively fixed.
|-
| 502.68
| 104.9317
| Al between Cl atoms inward movement, other atoms relatively fixed.
|}

== Mod 2: Week 2, AlCl<sub>2</sub>Br lowest energy dimer ==
==== Isomer 2 MO calculation ====
{{DOI|10042/}}<br>
[[File:vm1110_AlCl4Br2_isomer_3_mo.fchk]]<br>
'''File Type''': .fchk<br>
'''Calculation Type''': SP<br>
'''Calculation Method''': RB3LYP<br>
'''Basis Set''': Gen<br>
'''Charge''': 0<br>
'''Spin''': Singlet<br>
'''E(RB3LYP)''': -2352.41632880 au<br>
'''RMS Gradient Norm''': 0.0000000 au<br>
'''Dipole Moment''': 0.1920 Debye<br>
'''Point Group''': CS<br>
'''Job cpu time''': <br>

==== MO visualisations ====
{| class="wikitable" border="1"
|-
!MO
! AO interaction Weak or strong?
! AO interaction Bonding or antibonding?
! Nodes
! Delocalisation
|-
|[[File:vm1110_AlCl4Br2_isomer_1_mo_1.png|200px]]
| weak
| pi antibonding between the two 2 s orbitals on bridging Cl
| 1 node in the centre of the molecule
| Highly delocalised
|-
|[[File:vm1110_AlCl4Br2_isomer_1_mo_2.png|200px]]
| weak
| pi antibonding between two s orbitals on terminal Cl
| 1 node between terminal Cl atoms
| moderately delocalised
|-
|[[File:vm1110_AlCl4Br2_isomer_1_mo_3.png|200px]]
| weak
| pi antibonding between two s orbitals on terminal Br
| 1 node between terminal Br atoms
| moderately delocalised
|-
|[[File:vm1110_AlCl4Br2_isomer_1_mo_4.png|200px]]
| Weak interactions
| Antibonding between two p orbitals on terminal Cl. Bonding interaction between bridging Cl MOs
| node between and on terminal Cl atoms, nodes on bridging Cl atoms
| Terminal Cl MOs highly delocalised, bridging Cl MOs not very delocalised
|-
|[[File:vm1110_AlCl4Br2_isomer_1_mo_5.png|200px]]
| Weak interactions
| Antibonding between two p orbitals on terminal Br. Bonding interaction between bridging Cl MOs
| node between and on terminal Br atoms, nodes on bridging Cl atoms
| Terminal Br MOs highly delocalised, bridging Cl MOs not very delocalised
|}

The above table shows a selection of 5 filled non-core molecular orbitals ranging from the most bonding (top) to very antibonding (bottom).

== References ==
<references>
<ref name="Tl_Br_bond">{{cite journal|title = Structure of Thallium(III) Chloride, Bromide, and Cyanide Complexes in Aqueous Solution|journal = J. Am. Chem. Soc.|volume = 117|issue = 18|year = 1995 | pages = 5089-5104|doi = 10.1021/ja00123a011 | author1 = Johan Blixt | author2 =Julius Glasser | author3 = Janos Mink | author4 = Ingmar Persson | author5 = Per Persson | author6 = Magnus Sandstrom}}</ref>
</references>