Hayalex1

lab marking

You have a good working wiki. It would be good if you report values of wavenumber in your answers. Overall a very good attempt. If you have any specific questions, do email Prof. Hunt

NH₃

Calculation Data

Optimisation of NH₃ was performed using the following parameters:

Log file	AH_opf_pop.log
Molecule	NH3
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-56.55777 au
RMS gradient	0.000000
Point group	C3V

Log file

Media:AH_NH3_OPF_POP.LOG

Convergence data

The following data was collected from the log file, confirming convergence.

Item table

         Item               Value     Threshold  Converged?
 Maximum Force            0.000000     0.000015     YES
 RMS     Force            0.000000     0.000010     YES
 Maximum Displacement     0.000003     0.000060     YES
 RMS     Displacement     0.000001     0.000040     YES

Low frequencies

 Low frequencies ---   -5.6864   -3.6131   -3.6124    0.0017    0.0048    0.0162
 Low frequencies --- 1089.3674 1693.9284 1693.9284

Optimised molecule

Molecule parameters

• r(N-H): 1.02Â
  
• θ(H-N-H): 106°

Molecular structure

NH₃ top-down view

NH₃ 3D view

Vibrational analysis and IR spectrum

Mode	1	2	3	4	5	6
Wavenumber (cm-1)	1089	1694	1694	3461	3590	3590
Symmetry	A1	E	E	A1	E	E
Intensity	145	14	14	1	0	0

Charge distribution

Atom	N	H
Charge (e)	-1.13	+0.38

cis-N₂F₂ (Project molecule)

Calculation Data

Optimisation of N₂F₂ was performed using the following parameters:

Log file	AH_N2F2_OPTF_POP.LOG
Molecule	N2F2
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-309.01241 au
RMS gradient	0.000000
Point group	C2V

Log file

Media:AH_N2F2_OPTF_POP.LOG

Convergence data

The following data was collected from the log file, confirming convergence.

Item table

         Item               Value     Threshold  Converged?
 Maximum Force            0.000001     0.000015     YES
 RMS     Force            0.000000     0.000010     YES
 Maximum Displacement     0.000001     0.000060     YES
 RMS     Displacement     0.000001     0.000040     YES

Low frequencies

 Low frequencies ---    0.0014    0.0022    0.0022    3.2225    4.3532    5.1001
 Low frequencies ---  347.8772  561.2472  771.6105

Optimised molecule

Molecule parameters

• r(N-F): 1.39Â
• r(N=N): 1.22Â
• θ(F-N=N): 114°
• θ(F-N=N-F): 0°

Molecular structure

N₂F₂ 2D view

N₂F₂ 3D view

Vibrational analysis and IR spectrum

Data

Mode	1	2	3	4	5	6
Wavenumber (cm-1)	348	561	772	949	987	1637
Symmetry	A1	A2	B2	A1	B2	A1
Intensity	1	0	75	75	81	21

• The 3N-6 rule gives us an expected 6 vibrations (3 × 4 - 6 = 6).
• There are only 4 peaks on the IR spectrum because two of the vibrational modes have a negligible change in dipole moment, so they are not visible via IR spectroscopy.
• Vibrational mode 3 represents the asymmetric N-F stretching vibration.
• The highest energy mode is the N=N stretching vibration.

Charge distribution

cis-N₂F₂ has a charge separation driven by the high electronegativity of the fluorine atoms.

Atom	N	F
Charge (e)	+0.22	-0.22

Molecular orbital analysis

• MOs 1-4 correspond to the core orbitals of the atoms.

Molecular Orbital 9

The 9th molecular orbital of cis-N₂F₂ can be represented as the in-phase addition of the p_z orbitals on the N and F atoms.

BH₃

Calculation Data

Optimisation of BH₃ was performed using the following parameters:

Log file	AH_bh3_opt.log
Molecule	BH3
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-26.61532 au
RMS gradient	0.000002
Point group	D3h

Log File

Media:AH_BH3_OPT.LOG

Convergence data

The following data was collected from the log file, confirming convergence.

Item table

         Item               Value     Threshold  Converged?
 Maximum Force            0.000004     0.000015     YES
 RMS     Force            0.000003     0.000010     YES
 Maximum Displacement     0.000017     0.000060     YES
 RMS     Displacement     0.000011     0.000040     YES

Low frequencies

 Low frequencies ---  -11.6940  -11.6861   -6.5543   -0.0009    0.0280    0.4289
 Low frequencies --- 1162.9745 1213.1390 1213.1392