Rep:Mod:00636773

Introduction

In this project, Gaussian was explored to calculate electronic and physical properties of small molecules and the results were compared to literature. The molecules were BH₃, BBr₃, GaBr₃ and TlBr₃. Additionally, the B-N bond strength of NH₃BH₃ and the B-O bond strength of BH₃(THF) were calculated. The MO diagram of BH₃ and the NBO analysis of NH₃ were included.

Borane Optimisation

A molecule of borane, BH₃ was drawn and optimised first using a 3-21G and then a 6-31G basis set. These values cannot be compared for reasons stated later on.

Optimisation Results

Property	3-21G	6-31G	Ultrafine 6-31G	Ultrafine Frequency analysis
File type:	.log	.log	.log	.log
Calculation type:	FOPT	FOPT	FOPT	FREQ
Calculation method:	RB3LYP	RB3LYP	RB3LYP	RB3LYP
Basis set:	3-21G	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)
Final energy:	-26.46226338 a.u.	-26.61532363 a.u.	-26.46226364 a.u.	-26.61532364 a.u.
Gradient:	0.00020672 a.u.	0.00000235 a.u.	0.00000146 a.u.	0.00000146 a.u.
Dipole moment:	0 Debye	0 Debye	0 Debye	0 Debye
Point group:	D3H	D3H	D3H	D3H
Calculation time:	8.0 seconds	21.8 seconds	3.0 seconds	5.0 seconds
Log file:	BH3 3-21G	BH3 6-31G	BH3 Ultrafine	BH3 Ultrafine Frequency Analysis

A lower energy was observed for the 6-31G basis set. This is because it improves the simulation of polarisation of electrons as well as better modelling of the core orbitals, while using more processing time.

For 3-21G Basis Set:

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.

For 6-31G Basis Set:

Item               Value     Threshold  Converged?
 Maximum Force            0.000005     0.000450     YES
 RMS     Force            0.000003     0.000300     YES
 Maximum Displacement     0.000019     0.001800     YES
 RMS     Displacement     0.000012     0.001200     YES
 Predicted change in Energy=-1.305135D-10
 Optimization completed.
    -- Stationary point found.

Gallium Bromide and Thallium Bromide Optimisation

Gallium and thallium bromide were optimised using the same basis set, LANL2DZ.

Optimisation Results

Property	GaBr₃	TlBr₃
File type:	.log	.log
Calculation type:	FOPT	FOPT
Calculation method:	RB3LYP	RB3LYP
Basis set:	LANL2DZ	LANL2DZ
Final energy:	-41.700827827 a.u.	-91.218128507 a.u.
Gradient:	0.00000016 a.u.	0.00000090 a.u.
Dipole moment:	0 Debye	0 Debye
Point group:	D3H	D3H
Calculation time:	27.5 seconds	38.4 seconds
Link to D-Space:	DOI:10042/25225
Log file:	GaBr3 HPC	TlBr3 HPC

The final energy for thallium bromide was significantly lower than that of gallium bromide due to there being many more electrons in the thallium atom.

For GaBr₃:

Item               Value     Threshold  Converged?
 Maximum Force            0.000000     0.000450     YES
 RMS     Force            0.000000     0.000300     YES
 Maximum Displacement     0.000003     0.001800     YES
 RMS     Displacement     0.000002     0.001200     YES
 Predicted change in Energy=-1.282691D-12
 Optimization completed.
    -- Stationary point found.

For TlBr₃:

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.

Geometry

Property	GaBr₃ Gaussian	GaBr₃ Literature	TlBr₃ Gaussian	TlBr₃ Literature
Bond length:	2.350Å	2.239Å ^[1]	2.651Å	2.618Å ^[2]
Bond angle:	120.0°

Boron Triboride Optimisation

Boron tribromide was optimised using the "GEN" function, allowing custom basis sets to be used on individual atoms. 6-31G was used for boron, and LANL2DZ was used for the larger bromines.

Optimisation Results

Property	BBr₃
File type:	.log
Calculation type:	FOPT
Calculation method:	RB3LYP
Basis set:	Gen
Final energy:	-64.4364529566 a.u.
Gradient:	0.00000382 a.u.
Dipole moment:	0 Debye
Point group:	D3H
Calculation time:	36.8 seconds
Log files:	BBr3.gjf BBr3.log

Gaussian successfully settled on -64.43 a.u., about -160,177.92 kJ·mol^-1.

For BBr₃:

Item               Value     Threshold  Converged?
 Maximum Force            0.000008     0.000450     YES
 RMS     Force            0.000005     0.000300     YES
 Maximum Displacement     0.000036     0.001800     YES
 RMS     Displacement     0.000023     0.001200     YES
 Predicted change in Energy=-4.026916D-10
 Optimization completed.
    -- Stationary point found.

Geometry

B-Br Bond Length: 1.934Å compared to literature 1.900Å using gas diffraction ^[3]

Comparison of BH₃, BBr₃, GaBr₃ and TlBr₃

The bond lengths were calculated for the titled molecules and compared to the sum of their covalent radii.

Molecule	BH₃	BBr₃	GaBr₃	TlBr₃
Bond length:	1.193Å	1.934Å	2.350Å	2.651Å
Bond length using covalent radii:	1.17Å	2.04Å	2.42Å	2.65Å
Difference in electronegativity:	-0.16	-0.92	-1.15	-1.34
Bond angle:	120.0°

Atom	Boron	Gallium	Thallium	Hydrogen	Bromine
Atomic Radius:	0.90Å	1.35Å	1.70Å	0.65Å	1.20Å
Covalent Radius:	0.84Å	1.22Å	1.45Å	0.31Å	1.20Å

As expected, changing the ligand affects bond distances. They follow the expected trend that the larger the atom, the greater the bond length. In each of the above cases, the ligand is δ^-, but replacing hydrogen with bromine causes a greater difference in electronegativiy and increasing the Lewis acidity of the trigonal planar molecules.

Thallium (III) bromide is interesting in that the bond length is almost exactly the combination of the covalent radii, despite having expected ionic character. In fact it is unstable, disproportionating into thallium (II), thallium (I) and bromine.

Sometimes the bond length is outside of GaussView's animator's tolerated distance and does not draw a bond. This does not mean there is not a bond however. Again, sometimes extra bonds may be drawn for the opposite reason (an example being the dimerisation of MX3 Lewis acids. A chemical bond is the attractive interaction between oppositely charged particles, typically between ions, or when a structure adopts a lower energy from electrons filling overlapping wavefunctions of the same phase. The most favourable overlap dictates the distance between nuclei, and so the bond length changes depending on the orbitals.

Frequency Analysis

In the following section, the IR spectrum was predicted for BH₃ and GaBr₃. 6 modes were observed for each molecule in agreement to the 3N-6 rules (N = Number of atoms in molecule), but one mode was not IR active due to a lack of change of dipole moment.

Borane Frequency Analysis

Property	6-31G Optimisation	Frequency Optimisation
File type:	.log	.log
Calculation type:	FOPT	FREQ
Calculation method:	RB3LYP	RB3LYP
Basis set:	6-31G(d,p)	6-31G(d,p)
Final energy:	-26.61532363 a.u.	-26.61532363 a.u.
Gradient:	0.00000235 a.u.	0.00000294 a.u.
Dipole moment:	0 Debye	0 Debye
Point group:	D3H	D3H
Calculation time:	21.8 seconds	6.0 seconds
Log file	BH3 6-31G	BH3 Freq

 Item               Value     Threshold  Converged?
 Maximum Force            0.000006     0.000450     YES
 RMS     Force            0.000003     0.000300     YES
 Maximum Displacement     0.000023     0.001800     YES
 RMS     Displacement     0.000012     0.001200     YES
 Predicted change in Energy=-2.041299D-10
 Optimization completed.
    -- Stationary point found.

Low frequencies ---   -0.9458   -0.8709   -0.0054    5.6809   11.6924   11.7306
 Low frequencies --- 1162.9961 1213.1825 1213.1852

The following table shows the animated vibrational modes of borane, ordered from lowest wavenumber to highest; below that, a simulated spectrum is shown.

Mode	Frequency	Relative intensity	Symmetry D_3H point group	Comments
1	1163.00	93	A2"	Totally symmetric Hydrogens wag through the z-axis Change of dipole moment through z-axis
2	1213.18	14	E'	Almost symmetric through a B-H bond Two hydrogens scissor
3	1213.19	14	E'	No symmetry Two hydrogens scissor while one rocks Isoenergetic with mode 2
4	2582.28	0	A1'	A uniform, symmetric stretching centered at the boron IR inactive as no shift in dipole moment
5	2715.45	126	E'	One hydrogen is fixed while the others stretch asymmetrically
6	2715.45	126	E'	Two hydrogens stretch symmetrically while the other stretches asymmetrically to them isoenergetic with mode 5

From left to right, Modes 6 and 5, Modes 3 and 2, and Mode 1
Note Mode 4 is IR inactive

The following "Low Frequencies" were found in the results, 5.6809 being the lowest positive wavenumber:

-0.9458   -0.8709   -0.0054    5.6809   11.6924   11.7306

As the wavenumber goes down, the energy of the absorbed photon also goes down until it reaches 0. Going past that, the molecule begins to emit a photon of higher energy than the absorbed photon. This suggests that the molecule is in an excited or transition state, and absorbing another photon causes it to relax to a state of lower energy than the excited state, and therefore the emitted photon is of higher energy.

GaBr3 Frequency Analysis

Property	Frequency Optimisation
File type:	.log
Calculation type:	FREQ
Calculation method:	RB3LYP
Basis set:	LANL2DZ
Final energy:	-41.70082783 a.u.
Gradient:	0.00000011 a.u.
Dipole moment:	0 Debye
Point group:	D3H
Calculation time:	16.4 seconds
Link to D-Space	DOI:10042/25235

The system converged with a very low gradient, and the "0" frequencies were close to 0.

Item               Value     Threshold  Converged?
 Maximum Force            0.000000     0.000450     YES
 RMS     Force            0.000000     0.000300     YES
 Maximum Displacement     0.000002     0.001800     YES
 RMS     Displacement     0.000001     0.001200     YES
 Predicted change in Energy=-6.142862D-13
 Optimization completed.
    -- Stationary point found.


Low frequencies ---   -0.5252   -0.5247   -0.0024   -0.0010    0.0235    1.2010
 Low frequencies ---   76.3744   76.3753   99.6982

Mode	Frequency	Relative ntensity	Symmetry D_3H point group	Comments
1	76.37	3	E'	One bromine rocks about its own Ga-Br bond
2	76.38	3	E'	Two bromines scissor while the remaining gallium-bromine pair stretches asymmetrically to the bromines Isoenergetic to mode 1
3	99.70	9	A2"	Totally symmetric All 3 bromines wagging
4	197.34	0	A1'	A uniform, symmetric stretching centered at the gallium IR inactive as no shift in dipole moment
5	316.18	57	E'	Asymmetric wagging of two bromines as the third is fixed Large shift of dipole moment makes this mode highly active
6	316.19	57	E'	One bromine stretches with the gallium while the remaining bromines are fixed Isoenergetic with mode 5

From left to right, Modes 6 and 5, Mode 3, and Modes 2 and 1
Note mode 4 is IR inactive

A very strong absorption is observed at 316.18 wavenumbers, while the peak at 197.34 is not visible due to a lack of change of dipole moment.

Comparison of BH₃ and GaBr₃

Frequency analysis was completed for borane and gallium bromide using the same basis set and method. Basis sets use algorithms that take different components of systems into account, and so these components considered must be the mutually present for each system being compared. The Pople basis sets 3-21G and 6-31G were used for most of these calculations, while LANL2DZ (Los Alamos National Laboratoty 2 Double Zeta), a split basis set that makes a compromise between demand and accuracy, was used for larger centres.

A frequency analysis is performed to check the system is actually at a ground state and its potential is at a local minimum. If the system is not, negative frequencies will be observed showing that emitted photons will be of higher energy.

BH₃ Mode	BH₃ Frequency	GaBr₃ Frequency	Frequency Ratio	BH₃ Intensity	GaBr₃ Intensity	Intensity Ratio
1 (GaBr₃ Mode 3):	1163.00	99.70	11.66	93	9	10
2:	1213.18	76.38	15.88	14	3	4
3 (GaBr₃ Mode 1):	1213.19	76.37	15.89	14	3	4
4:	2582.28	197.34	13	0	0	NaN
5:	2715.45	316.18	8.59	126	57	2
6:	2715.45	316.19	8.59	126	57	2

Using ratios, modes can be paired up between the molecules. It becomes clear that the molecules are relatively similar. What is noticeable however is that the borane oscillates about 10 times faster than its gallium bromide counterpart. A large part of this is due to bromine being so much larger than hydrogen.

Borane is also much more active in absorbing infrared, especially at the low wavenumbers.

In the table, the modes 1 and 3 for GaBr₃ have been switched over. This could be due to the fact that the bromines are not required to move as much as the hydrogens in the BH3. Therefore their relatively huge mass does not do much to lower the wavenumber.

The modes that involve a stretching (or nearly a stretching) tend to have a higher wavenumber. This is because the distortion involved is greater than that of bending and so the bond is "stiffer" in that direction.

The low frequencies were calculated to show the systems were at ground state.

Borane Molecular Orbital Diagram

The MOs of Borane were calculated using the 6-31G basis set.

Optimisation Results

Property	BH₃
File type:	.log
Calculation type:	SP
Calculation method:	RB3LYP
Basis set:	6-31G(d,p)
Final energy:	-26.61532363 a.u.
Gradient:
Dipole moment:	0 Debye
Point group:	D3H
Calculation time:	31.5 seconds
Link to D-Space	DOI:10042/25246

The following diagram shows the drawn LCAOs and computed MOs for borane.

The LCAOs and MOs are in very tight agreement. Importantly, the nodes match quite well. The HOMO is doubly degenerate. This might not seem obvious looking from a LCAO perspective as the pi orbitals from the boron are at 90° to each other, compared to the 60° of the two matched trihydrogen orbitals.

NBO Analysis of Ammonia

A "Natural Bond Orbital" Analysis was computed for ammonia.

Property:	6-31G Optimisation:	Frequency Analysis:	Energy Calculation:	NBO Calculation:	Ultrafine Optimisation:	Ultrafine Frequency Analysis:
File type:	.log	.log	.log	.log	.log	.log
Calculation type:	FOPT	FREQ	SP	SP	FOPT	FREQ
Calculation method:	RB3LYP	RB3LYP	RB3LYP	RB3LYP	RB3LYP	RB3LYP
Basis set:	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)
Final energy:	-56.55776856 a.u.	-56.55776856 a.u.	-56.55776856 a.u.	-56.55776856 a.u.	-56.55776872 a.u.	-56.55776872 a.u.
Gradient:	0.00000885 a.u.	0.00000890 a.u.			0.00000137 a.u.	0.00000125 a.u.
Dipole moment:	1.8464 Debye	1.8464 Debye	1.8464 Debye	1.8464 Debye	1.8465 Debye	1.8465 Debye
Point group:	C1	C1	C1	C1	C1	C1
Calculation time:	41.5 seconds	24.5 seconds	7.5 seconds	31.8 seconds	21.0 seconds	9.0 seconds
Link to D-Space:	DOI:10042/25274	DOI:10042/25276	DOI:10042/25277	DOI:10042/25278	NH3 Ultrafine	NH3 Ultrafine Frequency

Initial optimisation:

Item               Value     Threshold  Converged?
 Maximum Force            0.000024     0.000450     YES
 RMS     Force            0.000012     0.000300     YES
 Maximum Displacement     0.000079     0.001800     YES
 RMS     Displacement     0.000053     0.001200     YES
 Predicted change in Energy=-1.629718D-09
 Optimization completed.
    -- Stationary point found.

Frequency analysis:

Item               Value     Threshold  Converged?
 Maximum Force            0.000022     0.000450     YES
 RMS     Force            0.000009     0.000300     YES
 Maximum Displacement     0.000078     0.001800     YES
 RMS     Displacement     0.000039     0.001200     YES
 Predicted change in Energy=-1.607264D-09
 Optimization completed.
    -- Stationary point found.

Low frequencies ---  -30.6847   -0.0011   -0.0006    0.0003   20.2705   28.3113
 Low frequencies --- 1089.5554 1694.1245 1694.1864

Ultra fine optimisation:

Item               Value     Threshold  Converged?
 Maximum Force            0.000004     0.000015     YES
 RMS     Force            0.000002     0.000010     YES
 Maximum Displacement     0.000008     0.000060     YES
 RMS     Displacement     0.000004     0.000040     YES
 Predicted change in Energy=-1.781029D-11
 Optimization completed.
    -- Stationary point found.

Ultra fine frequency analysis:

Item               Value     Threshold  Converged?
 Maximum Force            0.000003     0.000450     YES
 RMS     Force            0.000001     0.000300     YES
 Maximum Displacement     0.000007     0.001800     YES
 RMS     Displacement     0.000003     0.001200     YES
 Predicted change in Energy=-1.750514D-11
 Optimization completed.
    -- Stationary point found.

Low frequencies ---   -9.2383   -8.2165   -6.3379   -0.0007    0.0012    0.0013
 Low frequencies --- 1089.3360 1693.9207 1693.9250

Red indicates strongly negative (-1)
Green indicates strongly positive (+1)

The NBO analysis shows, as expected, that the nitrogen is drawing electron density towards itself making it δ-.

Reacting Ammonia and Borane

The energy of ammonia borane was calculated and compared to the sum of the energies of ammonia and borane to produce an energy difference in kJ·mol^-1

The reaction is as follows:

NH₃ + BH₃ → NH₃BH₃

Therefore the energy of the O→B bond is:

ΔE = E(NH₃BH₃)) - E(NH₃) - E(BH₃)

Optimisation Results and Frequency Analysis

Property	NH₃BH₃ Optimisation	NH₃BH₃ Frequency analysis	NH₃BH₃ Ultrafine Optimisation	NH₃BH₃ Ultrafine Frequency analysis
File type:	.log	.log	.log	.log
Calculation type:	FOPT	Freq	FOPT	Freq
Calculation method:	RB3LYP	RB3LYP	RB3LYP	RB3LYP
Basis set:	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)
Final energy:	-83.22468907 a.u.	-83.22468907 a.u.	-83.22468909 a.u.	-83.22468909 a.u.
Gradient:	0.00005752 a.u.	0.00005744 a.u.	0.00000103 a.u.	0.00000098 a.u.
Dipole moment:	5.5625 Debye	5.5625 Debye	5.5646 Debye	5.5646 Debye
Point group:	C3	C3	C3	C3
Calculation time:	1 minute, 27.8 seconds	1 minute, 47.8 seconds	0 minutes, 21.0 seconds	0 minutes, 20.0 seconds
Link to D-Space:	DOI:10042/25266	DOI:10042/25272	NH3BH3 Ultrafine	NH3BH3 Ultrafine

For the optimisation:

Item               Value     Threshold  Converged?
 Maximum Force            0.000169     0.000450     YES
 RMS     Force            0.000036     0.000300     YES
 Maximum Displacement     0.000934     0.001800     YES
 RMS     Displacement     0.000376     0.001200     YES
 Predicted change in Energy=-1.195425D-07
 Optimization completed.
    -- Stationary point found.

For the frequency analysis:

Item               Value     Threshold  Converged?
 Maximum Force            0.000214     0.000450     YES
 RMS     Force            0.000057     0.000300     YES
 Maximum Displacement     0.001085     0.001800     YES
 RMS     Displacement     0.000467     0.001200     YES
 Predicted change in Energy=-1.671857D-07
 Optimization completed.
    -- Stationary point found.


Low frequencies ---  -16.4152   -0.1037   -0.0051    0.0952   15.9992   16.0799
 Low frequencies ---  263.0558  631.2038  638.3487

For the ultra fine optimisation:

Item               Value     Threshold  Converged?
 Maximum Force            0.000001     0.000015     YES
 RMS     Force            0.000001     0.000010     YES
 Maximum Displacement     0.000036     0.000060     YES
 RMS     Displacement     0.000016     0.000040     YES
 Predicted change in Energy=-5.305546D-11
 Optimization completed.
    -- Stationary point found.

For the ultra fine frequency analysis:

Item               Value     Threshold  Converged?
 Maximum Force            0.000004     0.000450     YES
 RMS     Force            0.000001     0.000300     YES
 Maximum Displacement     0.000037     0.001800     YES
 RMS     Displacement     0.000019     0.001200     YES
 Predicted change in Energy=-6.068981D-11
 Optimization completed.
    -- Stationary point found.


Low frequencies ---   -0.1418   -0.0945   -0.0215    2.3376    2.3723    4.7234
 Low frequencies ---  263.4467  632.9779  638.4653

The "0" frequencies were a little negative, but mode 1 was high enough to be considered accurate.

Molecule	Energy in a.u.	Energy in kJ·mol^-1
NH₃:	-56.55776872	-148,492.43
BH₃:	-26.61532364	-69,878.54
NH₃BH₃:	-83.22468907	-218,506.44
ΔE:	-0.05159688	-135.47

The energy difference represents a bond enthalpy of 135.47kJ·mol^-1, which is comparatively close to the recorded bond enthalpy of 130.12kJ·mol^-1^[4].

The BH3-THF Adduct

The reaction of ammonia and borane is not straightforward - in the gaseous phase, borane dimerises to diborane, and the reaction with ammonia gives the diammoniate salt. Typically, a borane THF adduct is used. The reaction of the borane monomer with THF was calculated on a 4-core computer and visualised on Gaussview. This was to demonstrate the performance of the new computers.

The reaction is as follows:

BH₃ + THF → BH₃(THF)

Therefore the energy of the O→B bond is:

ΔE = E(BH₃(THF)) - E(THF) - E(BH₃)

Property	THF Opt	THF Freq	BH₃(THF) Opt	BH₃(THF) Freq	BH₃(THF) Ultra Fine Opt	BH₃(THF) Ultra Fine Freq
File type:	.log	.log	.log	.log	.log	.log
Calculation type:	FOPT	Freq	FOPT	Freq	FOPT	Freq
Calculation method:	RB3LYP	RB3LYP	RB3LYP	RB3LYP	RB3LYP	RB3LYP
Basis set:	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)	6-31G(d,p)
Final energy:	-232.45493214 a.u.	-232.45293214 a.u.	-259.10941197 a.u.	-259.10941197 a.u.	-259.10941260 a.u.	-259.10941260 a.u.
Gradient:	0.00013314 a.u.	0.00013316 a.u.	0.00001641 a.u.	0.00001635 a.u.	0.00000495 a.u.	0.00000496 a.u.
Dipole moment:	1.8164 Debye	1.8164 Debye	5.6555 Debye	5.6555 Debye	5.6561 Debye	5.6561 Debye
Point group:	C1	C1	C1	C1	C1	C1
Calculation time:	2 minute, 45.0 seconds	2 minute, 32.0 seconds	18 minute, 31.0 seconds	2 minute, 32.0 seconds	4 minute, 45.0 seconds	6 minute, 16.0 seconds
Log File:	THF.LOG	THF Freq.LOG	BH₃(THF)	BH₃(THF) Freq	BH₃(THF UF)	BH₃(THF) UF Freq

After 32 cycles and 18 minutes of processing on a desktop computer, the system converged:

Item               Value     Threshold  Converged?
 Maximum Force            0.000043     0.000450     YES
 RMS     Force            0.000010     0.000300     YES
 Maximum Displacement     0.000816     0.001800     YES
 RMS     Displacement     0.000221     0.001200     YES
 Predicted change in Energy=-2.993833D-08
 Optimization completed.
    -- Stationary point found.

However, the lowest frequency was too low for the system to be considered accurate.

Low frequencies ---  -19.1565   -0.0009   -0.0008   -0.0001    4.8530   13.8187
 Low frequencies ---   56.1338  171.4582  206.2434


Item               Value     Threshold  Converged?
 Maximum Force            0.000044     0.000450     YES
 RMS     Force            0.000016     0.000300     YES
 Maximum Displacement     0.001248     0.001800     YES
 RMS     Displacement     0.000489     0.001200     YES
 Predicted change in Energy=-4.178289D-08
 Optimization completed.
    -- Stationary point found.

A further 7 cycles were used to bring the system closer to the ground state.

Item               Value     Threshold  Converged?
 Maximum Force            0.000014     0.000450     YES
 RMS     Force            0.000002     0.000300     YES
 Maximum Displacement     0.000235     0.001800     YES
 RMS     Displacement     0.000063     0.001200     YES
 Predicted change in Energy=-1.424183D-09
 Optimization completed.
    -- Stationary point found.

Here the lowest frequency is within the tolerance threshold of -15 wavenumbers.

 Low frequencies ---   -9.3408    0.0007    0.0009    0.0011    4.9592   13.6031
 Low frequencies ---   50.4086  171.7010  203.3594


Item               Value     Threshold  Converged?
 Maximum Force            0.000024     0.000450     YES
 RMS     Force            0.000005     0.000300     YES
 Maximum Displacement     0.000252     0.001800     YES
 RMS     Displacement     0.000095     0.001200     YES
 Predicted change in Energy=-2.588702D-09
 Optimization completed.
    -- Stationary point found.

Comparing the energies of BH₃(THF) with BH₃ and THF:

Molecule	Energy in a.u.	Energy in kJ·mol^-1
THF	-232.45493214	-610,310.47
BH₃:	-26.61532363	-69,878.54
BH₃(THF):	-259.10941260	-680,291.81
ΔE:	-0.0391562	-102.81

A bond energy of 102.81 kJ·mol^-1 was calculated. This is lower than the 135.46 kJ·mol^-1 of ammonia borane formation, showing that the reaction is still exothermic, despite splitting the adduct.

References

↑ Balázs Réffya, Mária Kolonitsb, Magdolna Hargittai "Gallium tribromide: molecular geometry of monomer and dimer from gas-phase electron diffraction", Journal of Molecular Structure, Volume 445, Issues 1–3, 6 April 1998, 139-148, ISSN 0022-2860DOI:10.1016/S0022-2860(97)00420-1
↑ Schwerdtfeger, P. and Ischtwan, J. 1993, "Theoretical investigations on thallium halides: Relativistic and electron correlation effects in T1X and T1X3 compounds (X[DOUBLE BOND]F, C1, Br, and I)" J. Comput. Chem., 14: 913–921 DOI:10.1002/jcc.540140806
↑ Santiso-Quiñones, G. and Krossing, I. 2008, Reference Values for the B-X Bond Lengths of BI₃ and BBr₃. Z. anorg. allg. Chem., 634: 704–707 DOI:10.1002/zaac.200700510 .
↑ Yirong Mo, Lingchun Song, Wei Wu, and Qianer Zhang, Charge Transfer in the Electron Donor−Acceptor Complex BH₃NH₃, J. Am. Chem. Soc., 2004, 126 (12), 3974–3982 DOI:10.1021/ja039778l

[1] Balázs Réffya, Mária Kolonitsb, Magdolna Hargittai "Gallium tribromide: molecular geometry of monomer and dimer from gas-phase electron diffraction", Journal of Molecular Structure, Volume 445, Issues 1–3, 6 April 1998, 139-148, ISSN 0022-2860DOI:10.1016/S0022-2860(97)00420-1

[2] Schwerdtfeger, P. and Ischtwan, J. 1993, "Theoretical investigations on thallium halides: Relativistic and electron correlation effects in T1X and T1X3 compounds (X[DOUBLE BOND]F, C1, Br, and I)" J. Comput. Chem., 14: 913–921 DOI:10.1002/jcc.540140806

[3] Santiso-Quiñones, G. and Krossing, I. 2008, Reference Values for the B-X Bond Lengths of BI₃ and BBr₃. Z. anorg. allg. Chem., 634: 704–707 DOI:10.1002/zaac.200700510 .

[4] Yirong Mo, Lingchun Song, Wei Wu, and Qianer Zhang, Charge Transfer in the Electron Donor−Acceptor Complex BH₃NH₃, J. Am. Chem. Soc., 2004, 126 (12), 3974–3982 DOI:10.1021/ja039778l

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[2]

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Introduction

Borane Optimisation

Optimisation Results

Gallium Bromide and Thallium Bromide Optimisation

Optimisation Results

Geometry

Boron Triboride Optimisation

Optimisation Results

Geometry

Comparison of BH3, BBr3, GaBr3 and TlBr3

Frequency Analysis

Borane Frequency Analysis

GaBr3 Frequency Analysis

Comparison of BH3 and GaBr3

Borane Molecular Orbital Diagram

Optimisation Results

NBO Analysis of Ammonia

Reacting Ammonia and Borane

Optimisation Results and Frequency Analysis

The BH3-THF Adduct

References

Comparison of BH₃, BBr₃, GaBr₃ and TlBr₃

Comparison of BH₃ and GaBr₃