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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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 NH₄Cl (Ammonium chloride)

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		3318	3307	11.5	1.003		1.027	1.027	0.000	1.000		5.38	5.53	-0.15	0.973
2	A1	A1		2466	2207	258.1	1.117		1.039	1.042	-0.003	0.997		1035.31	1652.86	-617.55	0.626
3	A1	A1		1144	1151	-6.2	0.995		1.188	1.197	-0.009	0.993		199.93	134.36	65.57	1.488
4	A1	A1		165	198	-32.3	0.836		5.384	5.154	0.230	1.045		9.77	23.59	-13.82	0.414
5	E	E		3438	3451	-12.6	0.996		1.092	1.091	0.001	1.001		10.40	15.64	-5.24	0.665
6	E	E		3438	3451	-12.6	0.996		1.092	1.091	0.001	1.001		10.40	15.64	-5.24	0.665
7	E	E		1654	1641	13.1	1.008		1.064	1.063	0.001	1.001		28.88	29.04	-0.16	0.994
8	E	E		1654	1641	13.1	1.008		1.064	1.063	0.001	1.001		28.88	29.04	-0.16	0.994
9	E	E		629	777	-148.5	0.809		1.048	1.050	-0.002	0.998		110.90	100.23	10.67	1.106
10	E	E		629	777	-148.5	0.809		1.048	1.050	-0.002	0.998		110.90	100.23	10.67	1.106
11	E	E		219	252	-32.6	0.871		1.066	1.069	-0.003	0.997		22.61	22.21	0.40	1.018
12	E	E		219	252	-32.6	0.871		1.066	1.069	-0.003	0.997		22.61	22.21	0.40	1.018
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.