National Institute of Standards and Technology

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

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XXI	Oddities

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

Compare vibrational frequencies for two calculations for HCNH (methyleneazane)

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	A'	A'		3219	3248	-28.5	0.991		1.075	1.100	-0.026	0.977		2.51	18.07	-15.57	0.139
2	A'	A'		2919	2885	34.2	1.012		1.088	1.261	-0.173	0.863		33.03	323.74	-290.71	0.102
3	A'	A'		1497	2339	-841.4	0.640		6.433	3.742	2.691	1.719		0.67	390.15	-389.47	0.002
4	A'	A'		1137	985	151.9	1.154		1.474	1.256	0.219	1.174		116.70	89.89	26.81	1.298
5	A'	A'		910	699	210.3	1.301		1.045	1.172	-0.126	0.892		45.48	332.42	-286.94	0.137
6	A"	A"		955	896	59.9	1.067		1.285	1.335	-0.050	0.962		8.56	12.02	-3.45	0.713
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.