FIRST-PRINCIPLES MOLECULAR-DYNAMICS ON MULTIPLE ELECTRONIC STATES - ACASE-STUDY OF NAI

We present the first application of first-principles molecular dynamic s to a chemical process occurring on more than one electronic state. T he example is the collisional chemi-ionization of NaI using a novel ab initio technique for the electronic states and a previously described full multiple spawning (FMS) classically motivated quantal method to describe the nuclear dynamics, The results for the dynamics are compar ed with fully exact quantal propagation, The FMS method which generate s quantal amplitudes and inherently conserves normalization is shown t o perform remarkably well for this heavy particle problem. The ab init io generated potentials and interstate couplings are compared with emp irical potentials for NaI. Particular attention is given to the locali zed molecular orbital/generalized valence bond (LMO/GVB) method used f or the electronic problem and to its interface with the equations of m otion for the nuclei. The ability to incorporate atomic input (such as the ionization potential or the electron affinity) into the LMO/GVB m ethod is emphasized. (C) 1996 American Institute of Physics.