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 HCNCH₂⁺ (2H-Azirine 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	A'	A'		3118	3302	-183.1	0.945		1.156	1.607	-0.451	0.719		211.01	743.06	-532.06	0.284
2	A'	A'		3014	3033	-18.9	0.994		1.042	1.043	-0.001	0.999		22.32	36.47	-14.16	0.612
3	A'	A'		1878	2577	-698.6	0.729		5.614	2.353	3.261	2.386		8.45	1427.97	-1419.52	0.006
4	A'	A'		1430	1445	-14.5	0.990		1.073	1.079	-0.006	0.995		2.12	4.23	-2.10	0.502
5	A'	A'		943	998	-55.1	0.945		1.486	1.261	0.226	1.179		37.08	31.24	5.83	1.187
6	A'	A'		834	953	-118.5	0.876		1.218	5.765	-4.547	0.211		73.91	10.16	63.75	7.274
7	A'	A'		663	788	-125.2	0.841		3.300	1.822	1.479	1.812		37.33	41.73	-4.40	0.895
8	A'	A'		385	538	-153.2	0.715		8.043	2.467	5.575	3.260		20.50	18.26	2.24	1.123
9	A"	A"		3160	3184	-24.6	0.992		1.133	1.133	-0.000	1.000		26.13	26.77	-0.63	0.976
10	A"	A"		1068	1117	-48.6	0.956		1.215	1.236	-0.022	0.983		4.23	2.01	2.22	2.105
11	A"	A"		809	879	-69.8	0.921		1.424	1.219	0.206	1.169		32.42	20.22	12.20	1.604
12	A"	A"		493	402	91.9	1.229		1.051	1.183	-0.132	0.888		33.23	1.84	31.39	18.038
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.