Cashisab

lab marking

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

NH₃ Molecule

Calculation data

Name of submitted log file	ISABELLAC OPTIMISATIONNH3.log
Molecule	NH3
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-56.557769
RMS gradient	0.000000
Point group	C3v

Convergence data

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

Maximum Force does not exceed 0.00045 au, and the average (RMS) force does not exceed 0.0003 au indicating that the energies have fully converged.

Low frequencies

Low frequencies --- -5.6864 -3.6131 -3.6124 0.0017 0.0048 0.0162
Low frequencies --- 1089.3674 1693.9284 1693.9284
Values on top line are within +/- 20cm^-1 indicating that the geometries have fully converged

Optimized molecule images

Logfile: Media:ISABELLAC OPTIMISATIONNH3.log

Rotatable image

Imported geometric parameters

Optimized bond distance for NH₃

• r(N-H)=1.02Â
  

Optimized bond angle for NH₃

• θ(H-N-H)=105°

Vibrations

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

Charges

Charge H atom	0.38
Charge Nitrogen	-1.13

N₂F₂Molecule

Calculation data

Name of submitted log file	ISABELLACASHN2F2OPTIMSATION.LOG
Molecule	N2F2
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-309.012413
RMS gradient	0.000005
Point group	C2v

Convergence data

Item Table

         Item               Value     Threshold  Converged?
 Maximum Force            0.000018     0.000450     YES
 RMS     Force            0.000012     0.000300     YES
 Maximum Displacement     0.000087     0.001800     YES
 RMS     Displacement     0.000050     0.001200     YES

Maximum Force does not exceed 0.00045 au, and the average (RMS) force does not exceed 0.0003 au indicating that the energies have fully converged.

Low frequencies

Low frequencies --- -0.0016 -0.0007 0.0005 2.3561 3.8813 4.6729
Low frequencies --- 347.9199 561.2466 771.6387
Values on top line are within +/- 20cm^-1 indicating that it has fully converged

Optimized molecule images

Logfile: Media:ISABELLACASHN2F2OPTIMSATION.LOG

Rotatable image

Imported geometric paramters

Optimized bond distance for N₂F₂

• r(N-F)=1.40Â
  
• r(N-N)=1.22Â
  

Optimized bond angle for N₂F₂

• θ(F-N-N)=114°

Vibrations

Mode	1	2	3	4	5	6
Wavenumber(cm-1)	348	561	772	950	987	1637
Symmetry	A1	A2	B2	A1	B2	A1
Intensity	1	0	75	75	81	21

Questions

• How many vibrations are expected from the 3N-6 rule?
  (3x4-6)= 6
• Why are there only 4 peaks in the IR spectrum?
  The vibrations at 348 cm-1 and 561cm-1 have basically no intensity. To show up on IR the vibration must involve a net change in dipole, but these vibrational modes do not.
• Which vibration is the asymmetric N-F stretch?
  3
• What is the nature of the highest energy vibration?
  N-N stretch

Charges

Charge Fluorine atom	-0.21
Charge Nitrogen	0.215

Orbital Analysis

• Which MOs are core orbital MOs?
  1,2,3,4.
• Provide a picture of MO 9 and beside it draw the LCAO diagram