Devni

lab marking

You have a good working wiki. It would be good if you round off reported values to correct significant figures and do include "type:NBO" in charge selection section. Overall, a good attempt. If you have any specific questions, do email Prof. Hunt

NH₃ molecule

Calculation data

Name of submitted file	ndev_nh3_opt.log
Molecule Name	NH3
Calculation Method	RB3LYP
Basis Set	6-31G(d,p)
Final energy in atomic units	-56.557769
RMS Gradient	0.00
Point Group	C3V

Geometry Data

• Optimized r(N-H) bond distance = 1.018Â
  
• Optimized θ(H-N-H) angle = 106°

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

Optimized Molecule Image

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Log File

Media:NDEV_NH3_OPT.LOG

Rotateable Jmol

Optimized NH3

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Spectra Data

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

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

Charges

Atom	H1	H2	H3	Nitrogen
Charge	0.38	0.38	0.38	-1.13

Project Molecule Cis-N₂F₂

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The molecule from the log file does not have bonds between the F and N atoms, what is going on here?
The molecule from the log file does not show because the N-F bond is long and weak, it is there but the N=N bond is much stronger and thus gets visualised while the N-F bond (though present) is cut off.

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Calculation data

Name of submitted file	devni_n2f2_opt.log
Molecule Name	Cis-N2F2
Calculation Method	RB3LYP
Basis Set	6-31G(d,p)
final energy (Hartree)	-309.012413
RMS Gradient	0.00
Point Group	C2V

Log file Link: Media: DEVNI_N2F2_OPT.LOG

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ITEM TABLE

Confirmation of optimization, all converged

        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

Geometry Data

• Optimized r(N-F) bond distance = 1.391Â
  
• Optimized r(N=N) bond distance = 1.220Â
  
• Optimized θ(F-N=N) angle = 114°

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Optimized Rotatable N2F2

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Frequency Analysis

Low frequencies ---   -0.0015   -0.0012   -0.0010    3.2225    4.3532    5.1001
Low frequencies ---  347.8772  561.2472  771.6105

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

 IR Questions 

o How many vibrations are expected from the 3N-6 rule? 3N-6 -> (3*4)-6 = 6 vibrations
o Why are there only 4 peaks in the IR spectrum? Despite there being 6 vibrational modes not all of these are IR active such as symmetric vibrations and as cis-N₂F₂ is small and highly symmetrical some of the movements may have no change in dipole moment, hence do not appear. They may also just be too weak.
o Which vibration is the asymmetric N-F stretch? Vibration 3
o What is the nature of the highest energy vibration? N=N stretch, they move in a straight line towards each other like magnets then pull apart.

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Charges

Range: -0.215 to +0.215

Atom Charges

N1	N2	F1	F2
0.22	0.22	-0.22	-0.22

Molecular Orbital and LCAO Diagram

The core orbital is the n=1, s orbital