Yuri L. Volobuev

Continuous surface switching: An improved time-dependent self-consistent-field method for nonadiabatic dynamics

We present a new semiclassical method for electronically nonadiabatic collisions. The method is a variant of the time-dependent self-consistent-field method and is called continuous surface switching. The algorithm involves a self-consistent potential trajectory surface switching approach that is designed to combine the advantages of the trajectory surface hopping approach and the Ehrenfest classical path self-consistent potential approach without their relative disadvantages. Viewed from the self-consistent perspective, it corresponds to “on-the-fly histogramming” of the Ehrenfest method by a natural decay of mixing; viewed from the surface hopping perspective, it corresponds to replacing discontinuous surface hops by continuous surface switching. In this article we present the method and illustrate it for three multidimensional cases. Accurate quantum mechanical scattering calculations are carried out for these three cases by a linear algebraic variational method, and the accurate values of reactive pro...

POTLIB 2001: A potential energy surface library for chemical systems☆

Abstract POTLIB 2001 is a computer program library of global chemical potential energy surface (PES) functions (91 functions in version 1.0) along with test data, a suite of utility programs, and a convenient user interface. The PES programs are written in ANSI standard FORTRAN77 and can be used to determine the Born–Oppenheimer potential energy of chemical systems as a function of the internal coordinates. The accompanying test data allow users to verify local implementations of this library. Finally, the utility programs permit use of this library in conjunction with a variety of chemical dynamics and chemical kinetics computer codes. Interface routines are provided for the POLYRATE and ABCRATE program packages of Truhlar and co-workers, the VENUS96 program package of Hase and co-workers, and the VARIFLEX program package of Klippenstein and co-workers; the routines in this library can also be used in conjunction with the DYNASOL program package of Zhang and co-workers. This article describes the library and the utility programs and outlines the systematic conventions used for interfaces in the computer programs contained in the library. Adherence to these conventions will allow future PESs to be compatible with this library.

Stabilization methods for quantum mechanical resonance states of four-body systems

We describe the methods used in a computer code for quantum mechanical calculations of bound and resonance states of four-body systems. Three stabilization techniques for identifying the resonances and estimating resonance widths are discussed: calculation of coordinate-space moments, application of an imaginary optical potential, and analytic continuation of a real discrete spectrum using rational polynomial interpolation. Computational implementation of these methods, recent improvements to the computer code, and parallelization strategies are described in detail.

An MIMD strategy for quantum mechanical reactive scattering calculations

This article describes a multiprocessor parallel computer program for quantum mechanical reactive scattering calculations by the linear algebraic outgoing wave variational principle. Two aspects of the parallelization are emphasized: (i) domain-based parallelization of multidimensional integrals and (ii) multithreaded and message passing strategies for parallelizing large, dense matrix operations.