TY - JOUR

T1 - Comparison of ab initio and empirical potentials for H-atom association with diamond surfaces

AU - De Sainte Claire, Pascal

AU - Song, Kihyung

AU - Hase, William L.

AU - Brenner, Donald W.

PY - 1996/2/1

Y1 - 1996/2/1

N2 - Canonical variational transition-state theory (CVTST) is used to compare H + CH3 and H + diamond {111} association rate constants calculated from the Brenner empirical potential function and molecular anharmonic potentials written with switching (MAPS) functions. Previous work [J. Am. Chem. Soc. 1987, 109, 2916; J. Chem. Phys. 1994, 101, 2476] has shown that the MAPS functions, derived from ab initio calculations, give rate constants in agreement with experiment. For the 300-2000 K temperature range, the Brenner potential function gives CVTST H + CH3 and H + diamond {111} association rate constants which are 159-30 and 49-7 times smaller, respectively, than the values from the MAPS functions. An analysis of the Brenner potential function shows that it inaccurately represents the intermediate and long-range H - C association potential, which controls the structure of the variational transition state and the CVTST rate constant. The MAPS functions give H + CH3 and H + diamond {111} variational transition states with similar properties. Angular momentum and external rotation have no effect on the H + diamond {111} association rate constant, which makes it approximately an order-of-magnitude smaller than that for H + CH3 association.

AB - Canonical variational transition-state theory (CVTST) is used to compare H + CH3 and H + diamond {111} association rate constants calculated from the Brenner empirical potential function and molecular anharmonic potentials written with switching (MAPS) functions. Previous work [J. Am. Chem. Soc. 1987, 109, 2916; J. Chem. Phys. 1994, 101, 2476] has shown that the MAPS functions, derived from ab initio calculations, give rate constants in agreement with experiment. For the 300-2000 K temperature range, the Brenner potential function gives CVTST H + CH3 and H + diamond {111} association rate constants which are 159-30 and 49-7 times smaller, respectively, than the values from the MAPS functions. An analysis of the Brenner potential function shows that it inaccurately represents the intermediate and long-range H - C association potential, which controls the structure of the variational transition state and the CVTST rate constant. The MAPS functions give H + CH3 and H + diamond {111} variational transition states with similar properties. Angular momentum and external rotation have no effect on the H + diamond {111} association rate constant, which makes it approximately an order-of-magnitude smaller than that for H + CH3 association.

UR - http://www.scopus.com/inward/record.url?scp=0343602102&partnerID=8YFLogxK

U2 - 10.1021/jp951693m

DO - 10.1021/jp951693m

M3 - Article

AN - SCOPUS:0343602102

VL - 100

SP - 1761

EP - 1766

JO - Journal of Physical Chemistry

JF - Journal of Physical Chemistry

SN - 0022-3654

IS - 5

ER -