MO:hm1017
BH3
B3LYP/6-31G(d,p)
Item Value Threshold Converged? Maximum Force 0.000158 0.000450 YES RMS Force 0.000079 0.000300 YES Maximum Displacement 0.000622 0.001800 YES RMS Displacement 0.000311 0.001200 YES
Frequency fileː HUISHU_BH3_631_D3H_FREQ.LOG
Low frequencies --- -0.2456 -0.1129 -0.0054 44.0270 45.1846 45.1853 Low frequencies --- 1163.6049 1213.5924 1213.5951
BH3 |
Vibrational spectrum for BH3
| wavenumber(cm-1) | Intensity (arbitrary units) | symmetry | IR active? | type |
|---|---|---|---|---|
| 1163.60 | 92 | E' | yes | out-of-plane bend |
| 1213.59 | 14 | A2" | yes | bend |
| 1213.60 | 14 | E' | yes | bend |
| 2580.15 | 0 | E' | no | symmetric stretch |
| 2713.12 | 126 | A1' | yes | asymmetric stretch |
| 2713.12 | 126 | E' | yes | asymmetric stretch |
A vibrational mode absorbs infrared light when it is in a periodic change in the dipole moment of the molecule. Such vibrations are said to be infrared active. In general, the greater the polarity of the bond, the stronger its IR absorption. The symmetric stretch in BH3 (2580.15 cm-1) does not result in a change in dipole moment, and therefore does not result in any absorption of light.
Ng611 (talk) 21:40, 5 June 2019 (BST) This accounts for one of the missing IR bands, what about the other two missing bands?
PP and basis sets
Frequency file: HUISHU_BH3_631_D3H.LOG
Ng611 (talk) 21:39, 5 June 2019 (BST) This needed to be your frequency job, not your freq+opt job.
Item Value Threshold Converged? Maximum Force 0.000161 0.000450 YES RMS Force 0.000105 0.000300 YES Maximum Displacement 0.000638 0.001800 YES RMS Displacement 0.000418 0.001200 YES
optimised BH3 |
The optimized distance is 1.1927
MOs for BH3
There is no significant differences between the real and LCAO MOs. Hence when we draw the LCAO MOs, the real MOs can be used for a reference.
Ng611 (talk) 21:41, 5 June 2019 (BST) There are SOME differences though. What could they be?
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Association energies: Ammonia-Borane
NH3 B3LYP/6-31G(d,p) |
The optimized distance is 1.0179
NH3BH3 B3LYP/6-31G(d,p) |
The optimized distance are 1.2097(B-H), 1.6686 (B-N), 1.0184 (N-H)
NH3 Low frequencies --- -32.4235 -32.4224 -11.4276 -0.0047 0.0113 0.0475 Low frequencies --- 1088.7628 1694.0251 1694.0251 Item Value Threshold Converged? Maximum Force 0.000092 0.000450 YES RMS Force 0.000039 0.000300 YES Maximum Displacement 0.000305 0.001800 YES RMS Displacement 0.000102 0.001200 YES
Frequency file for NH3ː HSM_NH3_631_FREQ.LOG
NH3BH3 Low frequencies --- -25.5743 -13.3444 0.0008 0.0009 0.0012 10.9831 Low frequencies --- 262.9367 631.1057 637.2215 Item Value Threshold Converged? Maximum Force 0.000273 0.000450 YES RMS Force 0.000060 0.000300 YES Maximum Displacement 0.001506 0.001800 YES RMS Displacement 0.000384 0.001200 YES
Frequency file for NH3BH3ː HSM_NH3BH3_631_FREQ.LOG
E(NH3) = -56.55777 a.u.
E(BH3) = -26.61532 a.u.
E(NH3BH3) = -83.22469 a.u.
ΔE = E(NH3BH3) - [E(NH3)+E(BH3)] = -0.05160 a.u.
1 a.u. = 2625.5 kJ/mol
Hence ΔE = E(NH3BH3) - [E(NH3)+E(BH3)] = -0.05160 a.u. = -135.48 kJ/mol
Ng611 (talk) 21:43, 5 June 2019 (BST) Too many d.p. here.
It is a medium bond. The dative bond is weaker than commom covalent bond.
Ng611 (talk) 21:43, 5 June 2019 (BST) Good calculation, what is a common covalent bond? Provide a (referenced) example.
NI3
B3LYP/6-31G(d,p)
optimised NI3 |
The optimized distance is 2.1836
Ng611 (talk) 21:44, 5 June 2019 (BST) Too many d.p. here as well.
Frequency file: HSM_NI3_freq.LOG
Low frequencies --- -12.7349 -12.7287 -6.2860 -0.0040 0.0188 0.0634 Low frequencies --- 101.0320 101.0328 147.4112 Item Value Threshold Converged? Maximum Force 0.000063 0.000450 YES RMS Force 0.000038 0.000300 YES Maximum Displacement 0.000478 0.001800 YES RMS Displacement 0.000273 0.001200 YES
Project - Al2Cl4Br2
The five possible isomers
Isomer 1
B3LYP/6-31G(d,p)
Ng611 (talk) 21:47, 5 June 2019 (BST) You've not used a pseudopotential in your system and this has led you to incorrect values.
Symmetryː CS
Energyː -7469.09029 a.u.
1 a.u. = 2625.5 kJ/mol, hence energy is -19610097 kJ/mol
Al2Cl4Br2 Isomer 1 |
File: Alhm1.LOG
Item Value Threshold Converged? Maximum Force 0.000010 0.000450 YES RMS Force 0.000004 0.000300 YES Maximum Displacement 0.000798 0.001800 YES RMS Displacement 0.000279 0.001200 YES
Isomer 2
B3LYP/6-31G(d,p)
Symmetryː CS
Energyː -7469.08959 a.u.
1 a.u. = 2625.5 kJ/mol, hence energy is -19610095 kJ/mol
Al2Cl4Br2 Isomer 2 |
File: Alhm2.LOG
Item Value Threshold Converged? Maximum Force 0.000059 0.000450 YES RMS Force 0.000020 0.000300 YES Maximum Displacement 0.001628 0.001800 YES RMS Displacement 0.000580 0.001200 YES
Isomer 3
B3LYP/6-31G(d,p)
Symmetryː C1
Energyː -7469.13122 a.u.
1 a.u. = 2625.5 kJ/mol, hence energy is -19610204 kJ/mol
Al2Cl4Br2 Isomer 3 |
File: Alhm3.LOG
Item Value Threshold Converged? Maximum Force 0.000101 0.000450 YES RMS Force 0.000034 0.000300 YES Maximum Displacement 0.001656 0.001800 YES RMS Displacement 0.000719 0.001200 YES
Isomer 4
B3LYP/6-31G(d,p)
Symmetryː C1
Energyː -7469.13125 a.u.
1 a.u. = 2625.5 kJ/mol, hence energy is -19610204 kJ/mol
Al2Cl4Br2 Isomer 4 |
File: Alhm4.LOG
Item Value Threshold Converged? Maximum Force 0.000025 0.000450 YES RMS Force 0.000010 0.000300 YES Maximum Displacement 0.000375 0.001800 YES RMS Displacement 0.000174 0.001200 YES
Isomer 5
B3LYP/6-31G(d,p)
Symmetryː C1
Energyː -7469.13125 a.u.
1 a.u. = 2625.5 kJ/mol, hence energy is -19610204 kJ/mol
Al2Cl4Br2 Isomer 5 |
File: Alhm5.LOG
Item Value Threshold Converged? Maximum Force 0.000197 0.000450 YES RMS Force 0.000051 0.000300 YES Maximum Displacement 0.000621 0.001800 YES RMS Displacement 0.000365 0.001200 YES
The energy of the isomers with (a) 2 bridging Br ions and (b) the isomer with trans terminal Br and bridging Cl ions
(a) is the isomer 1, with the energy -7469.09028905 a. u.
(b) is the isomer 3, with the energy -7469.13122002 a. u.
The energy of (b) is a little more negative, thus it is more stable. This is due to the steric factor. In the isomer 3, the two larger Br groups are far away from each other, so there is less repulsion between their lone pairs.
Ng611 (talk) 21:46, 5 June 2019 (BST) Correct trend obtained, although your values are incorrect due to your problem in inputting the pseudopotential.
The relative stability of these conformers with respect to the bridging ions
For the two bridge atoms, if they are different (one Br and one Cl), the energy will be more negative. Then it will be more stable.
The dissociation energy for the lowest energy conformer into 2AlCl2Br
optimised AlCl2Br (B3LYP/6-31G(d,p)) |
The lowest energy conformer is the isomer 4, which has the most negative energy.
E(AlCl2Br) = -3734.74851982 a.u.
E(Al2Cl4Br2) = -7469.13125448 a.u.
ΔE = E(Al2Cl4Br2) - [E(AlCl2Br)+E(AlCl2Br)] = 0.36578516 a.u.
1 a.u. = 2625.5 kJ/mol
Hence ΔE = E(Al2Cl4Br2) - [E(AlCl2Br)+E(AlCl2Br)] = 0.36578516 a.u. = 960 kJ/mol
The product is less stable than the isolated monomers, due to the positive ΔE.
MO calcualtion on the lowest energy isomer
Isomer 4 is the lowest energy isomer.
Al2Cl4Br2 Isomer 4 |
3 MOs ranging from highly bonding to highly antibonding
MO74
(1) strong directed p-p sigma overlap, hence strong anti-bonding interaction
(2) weak p-p pi overlap, hence weak bonding interaction
(3) weak long range through space p-p bonding interactions
(4) nodes on atoms less important
In conclusion, it is highly antibonding.
MO73
(1) strong directed p-p sigma ovrelap, hence strong anti-bonding interaction
(2) weak p-p pi antibonding interactions
(3) medium non-directed p-p overlap bonding interaction
(4) weak long range through space antibonding interactions
(5) medium non-directed p-p through space anti-bonding interaction
(6) nodes between atoms increase anti-bonding character
In conclusion, it is highly anti-bonding.
MO70
(1) strong directed p-p sigma ovrelap, hence strong bonding interaction
(3) weak long range through space bonding interactions
(4) weak p-p pi bonding interactions
In conclusion, it is highly bonding.
Reference
1. http://www.huntresearchgroup.org.uk/teaching/teaching_comp_lab_year2a/Tut_MO_diagram_BH3.pdf