National Institute of Standards and Technology

Computational Chemistry Comparison and Benchmark DataBase
Release 22	May 2022
NIST Standard Reference Database 101

I	Introduction
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XX	H-bond dimers
XXI	Oddities

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III.G.7. (XIII.B.3.) (XIII.D.5.)

Compare vibrational frequencies for two calculations for H₂CN (Dihydrogen cyanide radical)

A = HF/6-31G*

B = MP2/6-31G*

scale factors=0.8985, 0.943

	symmetry			frequency (cm-1)					reduced mass (amu)					IR Intensity (km mol-1)
mode number	A	B		A	B	diff.	ratio		A	B	diff.	ratio		A	B	diff.	ratio
1	A1	A1		2908	2920	-12.7	0.996		1.047	1.058	-0.011	0.989		0.22	0.00	0.21	47.956
2	A1	A1		1473	1959	-486.5	0.752		1.770	8.939	-7.169	0.198		12.22	13.28	-1.06	0.920
3	A1	A1		1292	1376	-83.9	0.939		2.099	1.065	1.035	1.972		0.02	17.04	-17.01	0.001
4	B1	B1		928	1106	-178.2	0.839		1.345	1.362	-0.017	0.988		31.84	32.23	-0.39	0.988
5	B2	B2		2983	2984	-1.0	1.000		1.116	1.113	0.003	1.003		16.39	11.27	5.12	1.454
6	B2	B2		964	929	34.9	1.038		1.326	1.353	-0.027	0.980		15.05	7.11	7.94	2.117
scaled by				0.8985	0.943

See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.