A NEW METHOD FOR NUMERICAL FLUX CALCULATIONS IN QUANTUM MOLECULAR-DYNAMICS

The flux of an evolving wavepacket is the definite time integral of its probability current density. A new method for calculating the flux, based on a Chebychev polynomial expansion of the quantum evolution operator is presented. The central point of the development is that the time integration of the current density is performed analytically, resulting in a scheme which eliminates additional numerical errors. Using this method, one benefits from both the time-dependent and time-independent frameworks of the dynamics. Furthermore, the method requires only a small modification to the existing Chebychev polynomial evolution code. Examples of performance and accuracy and an application to the calculation of recombinative desorption probabilities of N-2 on Re are shown and discussed.