Table 5.

Comparison of experimental and computed harmonic ω and anharmonic ν wavenumbers for CO₂ (in cm⁻¹)

	B2PLYP[a]				HYBRID[b]				Best theo.		Expt.
State	ω				ω				ω	ν	ν
	669	664	642	664	673	668	646	668	673[c]	668[c]	668[c,d,e,f]
	1344	1275	1197	1285	1351	1284	1202	1293	1351[c]	1285[c,g]	1285[c,d,e,f,g]
	1337	1382	1374	1374	1346	1390	1381	1381		1388[g]	1388[d,e,f,g]
	1337	1330	1286	1330	1346	1338	1293	1338		1336[d]	1336[d,e,f]
	2006	1918	1752	1934	2018	1931	1759	1947		1933[d]	1934[d]
	2013	2070	2061	2055	2024	2082	2072	2066		2077[d]	2077[d,f]
	2390	2345	2345	2345	2391	2347	2347	2347	2391[c]	2349[c,g]	2349[c,d,e,f,g]
	2688	2526	2220	2581	2702	2543	2227	2597		2548[g]	2548[g]
	2674	2656	2660	2679	2691	2671	2673	2694		2671[g]	2671[g]
	2681	2791	2742	2714	2696	2797	2757	2729		2797[g]	2797[g]
	4780	4666	4666	4666	4782	4670	4670	4670		4673[g]	4673[g,f]
	3059	2997	2975	2997	3064	3003	2980	3003			3004[g,f]
	3734	3600	3517	3605	3742	3610	3524	3615		[d,e,g]	3613[d,e,f,g]
	3727	3706	3701	3701	3737	3715	3710	3710		[d,e,g]	3714[d,e,f,g]

The vibrational states are grouped by polyads.

^[a]AVQZ basis set.

^[b]harmonic CCSD(T)-F12a/AVTZ, from Ref.155, and anharmonic B2PLYP/AVQZ force fields.

Refs.: [c]¹⁵⁵, [d]¹⁶⁰, [e]¹⁶¹, [f]¹⁶², [g]¹⁵⁹.