Development of new quantum, semiclassical, and mixed quantum-classical methods for chemical dynamics simulations

Three new tools for understanding chemical dynamics are proposed and tested on model systems. Primary emphasis has been placed on understanding and improving upon semiclassical (SC) and mixed quantum-classical (MQC) simulation techniques. An efficient representation scheme for use in fully quantum mechanical methods is proposed as well. There are three primary achievements in this work. First, the semiclassical initial value representation (SC-IVR) has been implemented in a time-slicing algorithm, showing improvement over previous SC methods and approaching the limit of full quantum path integrals. Second, the Bohm approach to quantum mechanics has been used to examine the MQC simulation of electronically nonadiabatic dynamics and to understand drawbacks of current MQC approaches. Third, a new discrete variable representation has been devised for describing wavefunctions in a compact manner.