Constructing Potential Energy Surfaces for Polyatomic Systems: Recent Progress and New Problems

Table 3

NH₄ hydrogen abstraction saddle point properties.^a

	Interpolated (MC)b	Analytical (EC-2009)c	Ab initio d
Barrier height	14.64	14.48	14.73
Geometry
R(N–H′)	1.323	1.279	1.308
R(H′–HB)	0.900	0.868	0.890
<C–H′–HB	160.8	180.0	158.4
Vibrational frequencies
	3450	3444	3478
	3350	3373	3384
	2057	1861	1888
	1527	1623	1566
	1174	1497	1280
	1047	1080	1063
	650	622	677
	629	581	506
	1371i	1602i	1662i

aEnergy in kcal mol⁻¹, geometry in Å and degrees, and vibrational frequency in cm⁻¹; b[72]; c [39]; d [39], at the CCSD(T)/cc-pVTZ level.