TY - JOUR
T1 - What are the best affordable multi-coefficient strategies for calculating transition state geometries and barrier heights?
AU - Lynch, Benjamin J.
AU - Truhlar, Donald G.
PY - 2002/2/7
Y1 - 2002/2/7
N2 - We compare hybrid density functional theory and multi-coefficient correlation methods for locating saddle point geometries and calculating barrier heights on a Born-Oppenhiemer potential energy surface. We located reactant, product, and saddle point stationary points by the multi-coefficient Gaussian-3 (MCG3) method for 15 reactions, and by the multi-coefficient quadratic configuration interaction with single and double excitations (MC-QCISD) method for 22 reactions; and the resulting structures and energies are compared to those obtained by the Møller-Plesset second order perturbation theory (MP2), QCISD, and modified Perdew-Wang 1-parameter-for-kinetics (MPW1K) methods. We examined three single-level methods with two basis sets, 6-31+G(d,p) and MG3. By comparison to calculations on five systems where the saddle point has been optimized at a high level of theory, we conclude that the best saddle point geometries for the methods tested are those found at the MC-QCISD, MCG3, and MPW1K levels. MP2 was shown to have systematic deficiencies in predicting saddle point geometries. Our recommended most affordable methods are the MPW1K/6-31 +G(d,p) and MC-QCISD methods for fully optimized calculations and the MCG3//MPW1K/6-31 +G(d,p) method for single-point calculations with mean unsigned errors in calculating reaction energies and barrier heights of 1.6, 1.6, and 1.1 kcal/mol respectively.
AB - We compare hybrid density functional theory and multi-coefficient correlation methods for locating saddle point geometries and calculating barrier heights on a Born-Oppenhiemer potential energy surface. We located reactant, product, and saddle point stationary points by the multi-coefficient Gaussian-3 (MCG3) method for 15 reactions, and by the multi-coefficient quadratic configuration interaction with single and double excitations (MC-QCISD) method for 22 reactions; and the resulting structures and energies are compared to those obtained by the Møller-Plesset second order perturbation theory (MP2), QCISD, and modified Perdew-Wang 1-parameter-for-kinetics (MPW1K) methods. We examined three single-level methods with two basis sets, 6-31+G(d,p) and MG3. By comparison to calculations on five systems where the saddle point has been optimized at a high level of theory, we conclude that the best saddle point geometries for the methods tested are those found at the MC-QCISD, MCG3, and MPW1K levels. MP2 was shown to have systematic deficiencies in predicting saddle point geometries. Our recommended most affordable methods are the MPW1K/6-31 +G(d,p) and MC-QCISD methods for fully optimized calculations and the MCG3//MPW1K/6-31 +G(d,p) method for single-point calculations with mean unsigned errors in calculating reaction energies and barrier heights of 1.6, 1.6, and 1.1 kcal/mol respectively.
UR - http://www.scopus.com/inward/record.url?scp=0037034431&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037034431&partnerID=8YFLogxK
U2 - 10.1021/jp014002x
DO - 10.1021/jp014002x
M3 - Article
AN - SCOPUS:0037034431
SN - 1089-5639
VL - 106
SP - 842
EP - 846
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 5
ER -