QUANTUM DYNAMICS OF LARGE POLYATOMIC SYSTEMS USING CLASSICAL SEPARABLE POTENTIALS - THE COMPUTATIONAL IMPLEMENTATION

A novel approach for modeling of quantum dynamics and spectroscopy in large polyatomic systems is presented. The recently developed classica l separable potential (CSP) method propagates a multidimensional separ able quantum wavepacket using effective time-dependent single mode pot entials guided by classical trajectories. In this way, couplings betwe en individual degrees of freedom are taken into account in a mean-fiel d approximation. Comparison with ''numerically exact'' calculations fo r small systems and with experiments on large systems show that the CS P scheme is accurate and suitable for the description of short timesca le processes in the context of dynamical and spectroscopic application s. Moreover, calculations for systems having up to 10(3) coupled modes on scalar and up to 10(4) degrees of freedom on parallel computers ar e not computationally extremely demanding. This paper presents the pro gram package QDYN which implements the CSP method. Copyright (C) 1998 Elsevier Science Ltd.