Table 13.

Vibrational corrections α, rotational constants B_e and B₀ and quartic and sextic distortion constants for HCP, OCS, and C₂H₂ (in cm⁻¹)

	MP2	B3LYP[a]	B2PLYP	Best theo.	Expt.
HCP
	−0.00046[b]	−0.00058	−0.00047[b]	−0.00045[c]	−0.00045[d]
	0.00409	0.00346	0.00388	0.00362	0.00362[e]
	0.00313	0.00307	0.00313	0.00322	0.00318[d]
Be	0.65822	0.66174	0.66702	0.66931	—
B0	0.65506	0.65905	0.66400	0.66634	0.66633[c]
	−0.00316	−0.00269	−0.00302	−0.00297	—
	0.70884	0.64986	0.69155	0.70545[c]	0.70420[c,f]
OCS
	−0.00037[b]	−0.00035	−0.00036[a]	−0.00035[g]	−0.00034[g]
	0.00056	0.00068	0.00064	0.00066	0.00067
	0.00125	0.00121	0.00125	0.00123	0.00125
Be	0.20219	0.20030	0.20247	—	—
B0	0.20166	0.19971	0.20188	—	—
	−0.00053	−0.00059	−0.00059	—	—
	0.04063	0.04164	0.04223	0.04203	0.04270
C2H2
	−0.00137[h]	−0.00145	−0.00135[h]	−0.00141[i]	−0.00135[i,j]
	−0.00201	−0.00221	−0.00218	−0.00220	−0.00223
	0.00653	0.00556	0.00609	0.00584	0.00588
	0.00579	0.00575	0.00586	0.00601	0.00618
	0.00693	0.00672	0.00697	0.00686	0.00690
Be	1.16883	1.17463	1.18369	1.18245	—
B0	1.16259	1.16928	1.17775	1.17670	1.17665
	−0.00624	−0.00535	−0.00594	−0.00575	—
	1.58695	1.46786	1.56394	1.5902	1.627[f,k]
	0.89529	1.11004	1.08214	1.2631	1.6[f,k]

Basis sets: [a] SNSD; [b] AVQZ; [h] AVTZ.

Refs.: [c]¹⁹⁶; [d]¹⁹⁸; [e]¹⁹⁹; [g]¹⁵⁷; [i]¹⁶³; [j]⁵⁹; [k]¹⁹⁷.

[f] Ground state observed values.