State‐selective cross sections from ring polymer molecular dynamics

Abstract

Understanding the influence of different forms of energy (eg, translational, vibrational, rotational) on chemical reactions is a key goal and great challenge in physical chemistry. Very recently, we proposed a new approach to obtain state-selective cross sections that approximately include quantum effects such as zero-point energy and tunneling. The method is a combination of the widely used quasiclassical trajectory approach (QCT) and the ring polymer molecular dynamics method and thus is numerically very efficient and easily employed. Here, we present a detailed description of the method and exhaustive tests of its accuracy and applicability. The robustness of the approach is tested, as well as the convergence with the number of beads. The approach is then applied to several prototypical X + H 2 (ν = 0, 1), X = Mu, H, D, F, Cl reactions over a wide range of collision energies. Good agreement with rigorous quantum dynamics simulations is found for most cases. Encouraging improvement over QCT results is found for particular cases, while only a small increase in numerical cost is required.

Equilibrium–nonequilibrium ring-polymer molecular dynamics for nonlinear spectroscopy

“…Here, we present an alternative RPMD approach to two-dimensional spectroscopy, which directly considers the two-time response function and does not rely on the additional approximation related to the DKT correlation function. To derive the proposed method, we start from the recently developed nonequilibrium RPMD [69][70][71][72][73] and employ classical response theory. We then explore its validity and limitations both theoretically and numerically.…”

Path-integral approximations to quantum dynamics

“…This has been exploited recently with the development of nonequilibrium RPMD [133] (following earlier explorations of non-equilibrium CMD [134,135]), which has had interesting recent applications to hydrogen-graphene scattering [136,137], gas-surface reactions [138], and to excited-state dynamics [139]. Closely related to this are the recent developments of microcanonical RPMD [140][141][142].…”

Equilibrium-nonequilibrium ring-polymer molecular dynamics for nonlinear spectroscopy

“…Here, we present an alternative RPMD approach to two-dimensional spectroscopy, which directly approximates the two-time response function and does not rely on the additional approximation related to the DKT correlation function. To derive the proposed method, we start from the recently developed nonequilibrium RPMD [51][52][53][54][55] and employ classical response theory. We then explore its validity and limitations both theoretically and numerically.…”