Table 3. Fe(CO)₅ Assignments (cm^–1).

sym	mode no.	description	Edgell13	Bigorgne14	Catalotti15	Jones16	Delley18	Jonas19	Schaefer20	this work
			Expt.	Expt.	Expt.	Expt.	Calc.a	Calc.b	Calc.c
			gas	liquid	solid	gas				solid
A1′	ν1	ν(C≡O)	2117	2116	2115	2121	2072	2090	2169	2117
A1′	ν2	ν(C≡O)	1984	2030	2033	2042	1991	2012	2093	2021
A1′	ν3	ν(Fe–CO)	414	418	410	443	441	453	439	447
A1′	ν4	ν(Fe–CO)	377	381	440	413	419	428	413	419
A2′	ν5	δ(Fe–C≡O)		379	593	383	349	361	364	375
A2″	ν6	ν(C≡O)	2014	2022	2003	2034	1989	2011	2094	2020
A2″	ν7	δ(Fe–C≡O)	620	615	623	619	610	621	617	655/637
A2″	ν8	ν(Fe–CO)	474	430	433	429	480	485	473	427
A2″	ν9	δ(OC–Fe–CO)		72		[100]e	105	104	107	72
E′	ν10	ν(C≡O)	2034	2000	1980	2013	1974	1990	2067	1997
E′	ν11	δ(Fe–C≡O)	646	642	643	645	646	657	660	613
E′	ν12	δ(Fe–C≡O)	544	553	558	542	479	489	483	556
E′	ν13	ν(Fe–CO)	431	475	480	474	424	436	439	478
E′	ν14	δ(OC–Fe–CO)	104	114		105	103	100	104	106
E′	ν15	δ(OC–Fe–CO)	68	64		[74]e	54	50	54	84
E″	ν16	δ(Fe–C≡O)	752	488	487	488	539	552	563	447
E″	ν17	δ(Fe–C≡O)	492	448	614	[375]e	363	374	366	375
E″	ν18	δ(OC–Fe–CO)	95	130d		[97]e	94	93	95	129/122

^aB88-LYP with a double numerical basis set.

^bBP86 with an ECP2 basis set.

^cB3LYP with a double-ζ plus polarization (DZP) basis set.

^dSolid state.

^eEstimated from combination bands.