Rep:Mod:littlecutemolecule

NH₃ Molecule

Basic Information

A 3D NH3 Molecule

Molecule Name: NH₃

Calculation Method: RB3LYP

Basis Set: 6-31G(d,p)

E(RB3LYP): -56.55776873 a.u.

RMS Gradient Norm: 0.00000485 a.u.

Point Group: C3V

Optimized N-H bond distance: 1.01798 Å

Optimized H-N-H bond angle: 105.741 °

Real Data Of NH₃
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

Predicted change in Energy: -5.986276D-10

The optimisation file is liked to here

Frequency Analysis

There are six modes of vibrations for NH₃. Its frequencies spread from 1089.54s^-1 to 3589.82s^-1. Also, the peak intensities spread from 145.3814 to 0.2711.

Questions

1. How many modes do you expect from the 3N-6 rule?

  A: Six.

2. Which modes are degenerate (ie have the same energy)?

  A: 2&3, 5&6

3. Which modes are "bending" vibrations and which are "bond stretch" vibrations?

  A: Bending: 1,2,3  Bond Stretch: 4,5,6

4. Which mode is highly symmetric?

  A: Mode4

5. One mode is known as the "umbrella" mode, which one is this?

  A: Mode1

6. How many bands would you expect to see in an experimental spectrum of gaseous ammonia?

  A: Two.Since 2&3, 5&6 are degenerate, and 4&5&6 have negligible peak intensity, only the peak of mode1 and the peak of mode2&mode3 can be seen.

Atomic Charges

A screenshot of the charge distribution.

The charge on N is -1.125A and that on H is 0.375A.

Negative charge is expected on nitrogen and positive charge is expected on hydrogen since N is more electronegative than H.

N₂ Molecule

Basic Information

A 3D N2 Molecule

Molecule Name: N₂

Calculation Method: RB3LYP

Basis Set: 6-31G(d,p)

E(RB3LYP): -109.52359111 a.u.

RMS Gradient Norm: 0.02473091 a.u.

Point Group: D∞H

Optimized N-N bond distance: 1.09200 Å

Optimized N-N bond angle: 180.0 °

Real Data Of N₂
ITEM	VALUE	THRESHOLD	CONVERGED?
Maximum Force	0.000001	0.000450	YES
RMS Force	0.000001	0.000300	YES
Maximum Displacement	0.000001	0.001800	YES
RMS Displacement	0.000001	0.001200	YES

Predicted change in Energy=-3.401031D-13

The optimisation file is liked to here

Frequency Analysis

There is only one kind of vibration for N₂ molecule. According to the screenshot, there is a peak at 2457.33s^-1. However, since the intensity of the peak is 0.0000, no peak is expected to be observed on the spectrum.

Atomic Charges

The charge on N is 0, because it is a diatomic molecule, no electronegative difference.

H₂ Molecule

Basic Information

A 3D H2 Molecule

Molecule Name: H₂

Calculation Method: RB3LYP

Basis Set: 6-31G(d,p)

E(RB3LYP): -1.17853936 a.u.

RMS Gradient Norm: 0.00000017 a.u.

Point Group: D∞H

Optimized H-H bond distance: 0.74279 Å

Optimized H-H bond angle: 105.741 °

Real Data Of H₂
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

Predicted change in Energy=-1.164080D-13

The optimisation file is liked to here

Frequency Analysis

There is only one kind of vibration for H₂ molecule. According to the screenshot, there is a peak at 4465.68s^-1. However, since the intensity of the peak is 0.0000, no peak is expected to be observed on the spectrum.

Atomic Charges

The charge on H is 0, because it is a diatomic molecule, no electronegative difference.

Haber-Bosch process

Energy Calculations

E(NH3)=-56.55776873 a.u.

2*E(NH3)=-113.1155375 a.u.

E(N2)= -109.52359111 a.u.

E(H2)=-1.17853936 a.u.

3*E(H2)=-3.53561808 a.u.

ΔE=2*E(NH3)-[E(N2)+3*E(H2)]=-0.05632831 a.u.

Unit Conversion= -147.889989171 kJ/mol

The ammonia product is more stable.

literature value:ΔH_298K=-45.7kJ/mol ^[1]

The literature value is less exothermic than the calculated value.

ClF Molecule

Basic Information

A 3D ClF Molecule

Molecule Name: ClF

Calculation Method: RB3LYP

Basis Set: 6-31G(d,p)

E(RB3LYP): -559.93737432 a.u.

RMS Gradient Norm: 0.03767912 a.u.

Point Group: C∞V

Optimized Cl-F bond distance: 1.57000 Å

Optimized Cl-F bond angle: 180.000 °

Real Data Of ClF
ITEM	VALUE	THRESHOLD	CONVERGED?
Maximum Force	0.000246	0.000450	YES
RMS Force	0.000246	0.000300	YES
Maximum Displacement	0.000433	0.001800	YES
RMS Displacement	0.000613	0.001200	YES

Predicted change in Energy: -1.066055D-07

The optimisation file is liked to here

Frequency Analysis

There is only one kind of vibration for ClF molecule. According to the screenshot, there is a peak at 781.00s^-1. However, since the intensity of the peak is 11.6966, one peak is expected to be observed on the spectrum.

Atomic Charges

The charge on F is -0.337 and the charge on Cl is 0.337, because F is more electronegative than Cl.

Molecular Orbital

The third chosen molecular orbital is a 2s atomic orbital of Cl. The molecular orbital is not bonded and occupied. It is deep in energy and has not effect on bonding.

The fourth chosen molecular orbital is a mixture of 2s atomic orbital of F and 3s atomic orbital of Cl. The molecular orbital is bonded and occupied. It is deep in energy and tightens the bonding.

The last chosen molecular orbital is a mixture of 2s atomic orbital of F and 3s atomic orbital of Cl. The molecular orbital is anti-bonded and occupied. It is deep in energy and weakens the bonding.

References and bibliography

[1]G Austin,Shreve’s Chemical Process Industries, 5th ed., McGraw-Hill International Editions, New York, 1984.