TY - JOUR
T1 - Comparisons of classical and Wigner sampling of transition state energy levels for quasiclassical trajectory chemical dynamics simulations
AU - Sun, Lipeng
AU - Hase, William L.
N1 - Funding Information:
This material was based on work supported by the National Science Foundation under Grant Nos. CHE-0615321 and CHE-0957521, and the Robert A. Welch Foundation under Grant No. D-0005. Professor Jesus Santamaria is thanked for important discussions concerning sampling the Wigner distribution, and Professor Gyorgy Lendvay is thanked for helpful suggestions concerning the manuscript.
PY - 2010/7/28
Y1 - 2010/7/28
N2 - Quasiclassical trajectory calculations are compared, with classical and Wigner sampling of transition state (TS) energy levels, for C2 H5 F →HF+ C2 H4 product energy partitioning and [Cl CH3 Cl] - central barrier dynamics. The calculations with Wigner sampling are reported here for comparison with the previously reported calculations with classical sampling [Y. J. Cho, J. Chem. Phys. 96, 8275 (1992); L. Sun and W. L. Hase, J. Chem. Phys. 121, 8831 (2004)]. The C2 H5 F calculations were performed with direct dynamics at the MP2/6-31 G level of theory. Classical and Wigner sampling give post-transition state dynamics, for these two chemical systems, which are the same within statistical uncertainties. This is a result of important equivalences in these two sampling methods for selecting initial conditions at a TS. In contrast, classical and Wigner sampling often give different photodissociation dynamics [R. Schinke, J. Phys. Chem. 92, 3195 (1988)]. Here the sampling is performed for a vibrational state of the ground electronic state potential energy surface (PES), which is then projected onto the excited electronic state's PES. Differences between the ground and the excited PESs may give rise to substantially different excitations of the vibrational and dissociative coordinates on the excited state PES by classical and Wigner sampling, resulting in different photodissociation dynamics.
AB - Quasiclassical trajectory calculations are compared, with classical and Wigner sampling of transition state (TS) energy levels, for C2 H5 F →HF+ C2 H4 product energy partitioning and [Cl CH3 Cl] - central barrier dynamics. The calculations with Wigner sampling are reported here for comparison with the previously reported calculations with classical sampling [Y. J. Cho, J. Chem. Phys. 96, 8275 (1992); L. Sun and W. L. Hase, J. Chem. Phys. 121, 8831 (2004)]. The C2 H5 F calculations were performed with direct dynamics at the MP2/6-31 G level of theory. Classical and Wigner sampling give post-transition state dynamics, for these two chemical systems, which are the same within statistical uncertainties. This is a result of important equivalences in these two sampling methods for selecting initial conditions at a TS. In contrast, classical and Wigner sampling often give different photodissociation dynamics [R. Schinke, J. Phys. Chem. 92, 3195 (1988)]. Here the sampling is performed for a vibrational state of the ground electronic state potential energy surface (PES), which is then projected onto the excited electronic state's PES. Differences between the ground and the excited PESs may give rise to substantially different excitations of the vibrational and dissociative coordinates on the excited state PES by classical and Wigner sampling, resulting in different photodissociation dynamics.
UR - http://www.scopus.com/inward/record.url?scp=77955678781&partnerID=8YFLogxK
U2 - 10.1063/1.3463717
DO - 10.1063/1.3463717
M3 - Article
C2 - 20687656
AN - SCOPUS:77955678781
SN - 0021-9606
VL - 133
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 4
M1 - 044313
ER -