Rep:Mod:asdfgh1234

NH3 molecule

N-H bond distance = 1.01798

H-N-H bond angle = 37.129

Key information from optimised job

Molecule name = NH3

Calculation method = RB3LYP

Basis set = 6-31G(d,p)

Final energy E(RB3LYP) in atomic units = -56.55776873

Point group of molecule = C3V

Item table

 
         Item               Value     Threshold  Converged?
 Maximum Force            0.000004     0.000450     YES
 RMS     Force            0.000004     0.000300     YES
 Maximum Displacement     0.000072     0.001800     YES
 RMS     Displacement     0.000035     0.001200     YES

NH3 Molecule

The optimisation file is linked to here

Vibrations and charges

-6 modes would be expected from the 3N-6 rule

-Modes 2 + 3 and 5 + 6 are degenerate (ie have the same energy)

-Vibration modes 1, 2 + 3 are bending. Whereas, 4, 5 + 6 are stretching

-Mode 4 is highly symmetric

-Mode 1 is known as the "umbrella" mode

-You would expect to see 6 bands in an experimental spectrum of gaseous ammonia

Charge distribution

We would expect hydrogen to be positive and, as a consequence, the nitrogen to be negative

H = 0.375

N = -1.125

N2 Molecule

N-N bond distance = 1.09200

Key information from optimised job

Molecule name = Nitrogen gas

Calculation method = RB3LYP

Basis set = 6-31G(d,p)

Final energy E(RB3LYP) in atomic units = -109.52359111

Point group of molecule = D*H

Item table

 
         Item               Value     Threshold  Converged?
 Maximum Force            0.000001     0.000450     YES
 RMS     Force            0.000001     0.000300     YES
 Maximum Displacement     0.000000     0.001800     YES
 RMS     Displacement     0.000000     0.001200     YES

There was just one mode of vibration identified; frequency = 2457.33, infrared = 0

H2 Molecule

H-H bond distance = 0.60000

Key information from optimised job

Molecule name = Hydrogen gas

Calculation method = RB3LYP

Basis set = 6-31G(d,p)

Final energy E(RB3LYP) in atomic units = -1.15928020

Point group of molecule = D*H

Item table

 
         Item               Value     Threshold  Converged?
 Maximum Force            0.000000     0.000450     YES
 RMS     Force            0.000000     0.000300     YES
 Maximum Displacement     0.000000     0.001800     YES
 RMS     Displacement     0.000001     0.001200     YES

There was just one mode of vibration identified; frequency = 4465.68, infrared = 0

Reaction energies

N2 + 3H2 --> 2NH3

ΔE=2*E(NH3)-[E(N2)+3*E(H2)]= -0.11410576 a.u

-0.11410576*2625.5 = -299.58 kJ/mol

Choice of Small Molecule

Molecule = CH4

C-H Bond distance = 1.07000

Bond angle = 109.471

Key information from optimised job

Molecule name = Methane

Calculation method = RB3LYP

Basis set = 6-31G(d,p)

Final energy E(RB3LYP) in atomic units = -40.52275298

Point group of molecule = T

Item table

         Item               Value     Threshold  Converged?
 Maximum Force            0.000063     0.000450     YES
 RMS     Force            0.000034     0.000300     YES
 Maximum Displacement     0.000179     0.001800     YES
 RMS     Displacement     0.000095     0.001200     YES

CH4 Molecule

The optimisation file is linked to here

Vibrations and charges

Molecular Orbitals

Worth revisiting this when I am with the group in Chemistry

This MO is deep in energy. No overlap, held tightly to nuclei and not involved in chemical bonding

Combination of valence orbitals bonding and antibonding. Strong overlap, likely to be involved in chemical bonding

Orbitals lie along the bond. Sit side by side, etc.

Charge distribution

H = 0.233

C = -0.930