This document discusses frequency calculations using Gaussian09 software. Frequency calculations can (1) predict IR and Raman spectra of molecules, (2) compute force constants for geometry optimization, (3) identify the nature of stationary points on the potential energy surface, and (4) compute zero-point vibration and thermal energy corrections. The document provides examples of frequency calculation outputs for files F1.3, F2.3, and F3.3 that show frequencies and intensities, force constants, stationary points, and thermal corrections.

1. Frequency CaIculations
Presented by
Nguyen Duy The

2. Introduction
 Running frequency calculations using Gaussian09, frequency
calculations can serve a number of different purposes:
 To predict the IR and Raman spectra of molecules (frequencies and
intensities). (Content 1)
 To compute force constants for a geometry optimization. (Content 2)
 To identify the nature of stationary points on the potential energy
surface. (Content 3)
 To compute zero-point vibration and thermal energy corrections to
total energies as well as other thermodynamic quantities of interest
such and the enthalpy and entropy of the system (Conten 4)

3. Object: Benzen + Hydro ( C6H6 + H2)
• Files 1(F1) : th1.0benzen.cml + Benzen1.com + Benzen1.log
▫ F1.1: file structure after optimizating by Avogadro.
▫ F1.2: Input file for gaussian09
▫ F1.3: file log after running
• Files 2(F2): th2.1benzen.cml + Benzen2.com + Benzen2.log
• Files 3(F3): th2.2benzen.cml + Benzen3.com + Benzen2.log
Link:

4. Object: File .cml of C6H6 + H2
F1.1 F2.1 F3.1

5. Object: File .com of C6H6 + H2
# RHF/6-31G(d) Freq
Benzen Hydro
0 1
C 1.3694080000 0.0863440000 -0.0021330000
C 0.6820980000 0.1424780000 -1.2193950000
C -0.7167020000 0.1638500000 -1.2325740000
C -1.4281990000 0.1292130000 -0.0284710000
C -0.7408860000 0.0731960000 1.1887950000
C 0.6579120000 0.0516970000 1.2019680000
H 0.3043660000 3.1027220000 0.2819250000
H -0.2921620000 3.1290040000 -0.0983550000
H 2.4515430000 0.0699760000 0.0080640000
H 1.2325250000 0.1695200000 -2.1508930000
H -1.2484090000 0.2074550000 -2.1742600000
H -2.5103260000 0.1460220000 -0.0386510000
H -1.2913040000 0.0466400000 2.1203130000
H 1.1896260000 0.0085280000 2.14367100000

6. Content 1: Frequencies and intensities
Spectral line 1 2 3 4 5 6 7 8 9 10 11
Frequencies -
841.220
-
824.469
-
70.890
47.05 250 477 478 666.14 666.17 785 803
IR Int 0.6109 0.1142 0.0010 0.0012 0.0250 0.0026 0.0025 0.0003 0.0007 0.0012 108
Spectral line 12 13 14 15 16 17 18 19 20 21 22
Frequencies 985 986 1048 1091 1115 1116 1125 1126 1127 1149 1288
IR Int 0.0003 0.0178 0.0014 0 0.0125 0.0014 1.985 2.2798 0.1870 0.0008 0.0001

7. Content 1: Frequencies and intensities
Spectral line 23 24 25 26 27 28 29 30 0.0250 32 33
Frequencies 1288 1341 1511 1637.6 1637.9 1754.6 1754.8 3287 3297 3298 3316.0
IR Int 0.0081 0.0020 11.7435 0 11.8753 0.0004 0.0004 0.0004 0.0041 0.0059 61.145
Spectral line 34 35 36
Frequencies 3316.11 3327 4988
IR Int 61.7183 0.2191

8. Content 1: Frequencies and intensities

9. Content 2: Force constant
Spectral line 1 2 3 4 5 6 7 8 9 10 11
Force
constant
0.4206 0.4041 0.0036 0.0016 0.0388 0.3980 0.3996 1.6315 1.6314 1.2232 0.412
4
Spectral line 12 13 14 15 16 17 18 19 20 21 22
Force
constant
0.7121 0.7135 3.9086 4.551
7
0.9978 0.9960 1.4324 1.3819 2.6789 1.0008 1.1595
Spectral line 23 24 25 26 27 28 29 30 31 32 33
Force
constant
1.1600 1.2953 1.6781 2.9035 2.9055 7.8738 7.8795 6.9101 6.9833 6.9837 7.1003
Spectral line 34 35 36
Force
constant
7.1007 7.1714 14.777
6

10. Content 2: Force constant

11. Content 3: Stationary Points
• There are two pieces of information from the output which are critical
to characterizing a stationary point:
 The number of imaginary frequencies.
 The normal mode corresponding to the imaginary frequency.
lmanginary Frequencies are listed in the output of a frequency calculation
as negative numbers. By definition, a structure which has n imaginary
frequencies is an nth order saddle point

12. Content 3: Stationary Points
From: Exploring Chemistry with Electronic Structure Methods - James B. Foresman
Aleen Frisch

13. Content 3: Stationary Points
F1.3 F2.3 F3.3
The number of imaginary
frequencies
3 6 8

14. Content 4: The Zero-point and Thermal Energy-corrected
The zero-point energy is a correction to the electronic energy of the molecule or hamal mayy cdon. to account for
the effects of molecular vibrations which persist even at 0 K.
From: Exploring Chemistry with Electronic Structure Methods - James B. Foresman
Aleen Frisch

15. Content 4: The Zero-point and Thermal Energy-corrected
Zero-point vibrational energy 311597.0 (Joules/Mol) = 74.47348 (Kcal/Mol)
Zero-point correction= 0.118681 (Hartree/Particle)
Thermal correction to Energy= 0.124051
Thermal correction to Enthalpy= 0.124995
Thermal correction to Gibbs Free Energy= 0.089267
E0 Sum of electronic and zero-point Energies= -231.708133
(E) Sum of electronic and thermal Energies= -231.702763
(H) Sum of electronic and thermal Enthalpies= -231.701818
(G) Sum of electronic and thermal Free Energies= -231.737546

16. F1.3 F2.3 F3.3
Zero-point vibrational energy 311597.0 (Joules/Mol)
= 74.47348 (Kcal/Mol)
238397.0 (Joules/Mol)
56.97825 (Kcal/Mol)
237582.3 (Joules/Mol)
56.78352 (Kcal/Mol)
Zero-point correction 0.118681 (Hartree/Particle) 0.090801 (Hartree/Particle) 0.090490 (Hartree/Particle)
Thermal correction to Energy 0.124051 0.097207 0.096498
Thermal correction to Enthalpy 0.124995 0.098151 0.097443
Thermal correction to Gibbs Free
Energy
0.089267 0.061294 0.061095
(E0) Sum of electronic and zero-point
Energies
-231.708133 -193.443437 -230.767603
(E) Sum of electronic and thermal
Energies
-231.702763 -193.437031 -230.761595
(H) Sum of electronic and thermal
Enthalpies
-231.701818 -193.436087 -230.760651
(G) Sum of electronic and thermal
Free Energies
-231.737546 -193.472944 -230.796998
Content 4: The Zero-point and Thermal Energy-corrected

17. Content 1: Frequencies and intensities
F1.3 F2.3 F3.3

18. Content 1: Frequencies and intensities
F1.3 F2.3 F3.3

19. Content 2: Force constant
F1.3 F2.3 F3.3

20. Frequency CaIculations
Presented by
Nguyen Duy The