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.)

Molecule problem. Defaulted to H2CO

Compare vibrational frequencies for two calculations for H₂CO⁺ (formaldehyde cation)

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		2868	2779	89.0	1.032		1.043	1.032	0.011	1.011		75.10	155.12	-80.03	0.484
2	A1	A1		1568	1546	22.2	1.014		6.065	11.849	-5.784	0.512		9.30	0.78	8.53	11.977
3	A1	A1		1320	1265	54.5	1.043		1.145	1.060	0.085	1.080		67.87	75.30	-7.43	0.901
4	B1	B1		1146	1068	77.8	1.073		1.331	1.340	-0.009	0.994		16.03	37.33	-21.30	0.429
5	B2	B2		3003	2920	83.1	1.028		1.125	1.117	0.008	1.007		100.23	144.33	-44.11	0.694
6	B2	B2		968	855	112.8	1.132		1.315	1.337	-0.022	0.983		9.51	0.91	8.60	10.436
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.