Geertsabig

lab marking

You have a good working wiki. It would be good if you round off reported values to correct significant figures. The resolution of images could be better. Overall, a good attempt. If you have any specific questions, do email Prof. Hunt

NH₃ Molecule

Log File

Media:AMG NH3 OPTF 307.LOG

Calculation Data

The settings on gausview and the data from the optimised molecule summary.

name of log file	AMG_NH3_optf_307.log
Molecule	NH3
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-56.557769au
RMS gradient	0.0000000
Point group	C3v

Item Table

The item table from the .log file for the optimised NH₃ molecule. It shows that the molecule was optimised successfully because all the values fall below the threshold.

         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

Optimised Molecule Image

NH₃ fully optimised from as viewed from above.

Jmol rotatable Molecule

3D rotatable NH₃ molecule

The N atom is blue the three H atoms are white

Measurements of NH₃

Measurements from the optimised Molecule.

Bond angle

H-N-H 105°

Bond length

N-H 1.300 Å

Vibrations

The stretching and bending modes of the bonds in the molecule.

Table of modes

Wavenumber, intensity and symmetry of each vibrational mode.

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

IR spectrum

IR spectrum of NH₃ generated by gausview.

Modes 2 and 3 overlap with eachother and modes 4, 5 and 6 are too small to be visible so only 2 peaks are visible.

Log file data

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

Charge Distribution

Table

Atom	Charge (e)
N	-1.13
H	0.38

Image

Image showing the distribution of charge across the atoms in the molecule.

Gradient goes from red to green, -1.125 to 1.125

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Project Molecule

Log file

Media:ABI_G_N2F2_OPTF.LOG

Calculation Data

Method of optimisation and optimisation summary data.

name of log file	ABI_G_N2F2_OPTF.log
Molecule	N2F2
Method	RB3LYP
Basis set	6-31G(d,p)
Final energy	-309.012413 Eh
RMS gradient	0.0000000
Point group	C2v

Item table N₂F₂

The item table from the .log file for the optimised N₂F₂ molecule. It shows that the molecule was optimised successfully because all the values fall below the threshold.

         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

Image of N₂F₂

Image of optimised N₂F₂ molecule from side on

The length of the N-F bonds exceeds the bond length where gausview will show the bond.

Jmol Rotatable Molecule

3D rotatable N₂F₂ Molecule.

The N atoms are represented in blue and the F atoms are represented in green.

Measurement of N₂F₂

The lengths and angles of the bonds on the optimised N₂F₂

Bond length

F-N 1.39 Å

N-N 1.22 Å

Bond angles

F-N-N 114°

Vibrations

The stretching and bending modes of the bonds in the molecule. There are 3 bending modes and 3 stretching modes are present in N₂F₂.

Table of Vibrations

Wavenumber, intensity and symmetry of each vibrational mode

Mode	Wavenumber (cm-1)	Intensity	Symmetry
1	348	1	A1
2	561	0	A2
3	772	75	B2
4	949	75	A1
5	987	81	B2
6	1636	21	A1

IR spectrum

IR spectrum of N₂F₂ generated by gausview.

Modes 1 and 2 are too small to be visible. All the other modes show as a peak on the spectrum.

IR questions

1. How many vibrations are expected from the 3N-6 rule?
   • 6 are expected. 3(2 N atoms+2 F atoms)-6=6
2. Why are there only 4 peaks in the IR spectrum?
   • There are 4 peaks in the IR spectrum because vibrational modes 1 and 2 have such low intesitys that they do not make a visible peak. Therefore only the modes from 3 onwards are seen on the IR spectrum
3. Which vibration is the asymmetric N-F stretch?
   • Mode 3 is the asymmetric N-F stretch.
4. What is the nature of the highest energy vibration?
   • The highest energy vibration is mode 6 it is the N=N stretch.

Log file

The Low frequency lines from the .log file. The low frequencies being within -20 and 20 on the first line shows the molecule has been optimised to an acceptable level.

 Low frequencies ---   -0.0018   -0.0017   -0.0012    3.2233    4.3533    5.0998
 Low frequencies ---  347.8772  561.2472  771.6105

Charge Distribution

Table

The values of the charge on each atom.

Atom	Charge (au)
N	0.22
F	-0.22

Image

Image showing the charge distribution of the N₂F₂

Gradient goes from red to green, -0.215 to 0.215

Molecular orbitals

The MOs describe electron density and bonding in the molecule.

Questions

1. Which MOs are core orbital MOs?
   • MOs 1, 2, 3 and 4 are core orbitals. They are orbitals that only have S orbitals of either the F atoms, 1 and 2, or the N atoms, 3 and 4.

MO 9 image

MO 9 as generated by gausview

LACO diagram

The LACO diagram for N₂F₂