Extended Hamiltonian molecular dynamics: semiclassical trajectories with improved maintenance of zero point energy. Issue 48 (29th November 2018)

• Record Type: Journal Article
• Authors: Shu, Yinan; Dong, Sijia S.; Parker, Kelsey A.; Bao, Junwei L.; Zhang, Linyao; Truhlar, Donald G.
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 48(2018)
• Page Start: 30209
• Page End: 30218
• Publication Date: 2018-11-29
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp04914a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : We present a new semiclassical molecular dynamics method designed to improve the treatment of the zero-point energy in quasiclassical trajectories. Abstract : It is well known that classical trajectories, even if they are initiated with zero point energy (ZPE) in each mode (trajectories initiated this way are commonly called quasiclassical trajectories), do not maintain ZPE in the final states. The energy of high-frequency modes will typically leak into low-frequency modes or relative translation of subsystems during the time evolution. This can lead to severe problems such as unphysical dissociation of a molecule, production of energetically disallowed reaction products, and unphysical product energy distributions. Here a new molecular dynamics method called extended Hamiltonian molecular dynamics (EHMD) is developed to improve the ZPE problem in classical molecular dynamics. In EHMD, two images of a trajectory are connected by one or more springs. The EHMD method is tested with the Henon–Heiles Hamiltonian in reduced and real units and with a Hamiltonian with quartic anharmonicity in real units, and the method is found to improve zero-point maintenance as intended.