Quantum corrections to parameters of interatomic distance distributions in molecular dynamics simulations

Abstract

The problem of computation of interatomic distance distributions is considered in the context of gas electron diffraction method. A new theoretical approach has been developed for calculation of mean square amplitudes, corrections for interatomic distances and asymmetry parameters on the basis of ab initio molecular dynamics simulations with a posteriori quantum corrections. Several approximations have been evolved, and corresponding algorithms have been coded. Their testing has been performed by calculation of parameters for a set of diatomic molecules, ethane and 9,12-I2-1,2-dicarba-closo-dodecaborane. Comparison of the obtained amplitudes and distance corrections with those calculated by conventional methods demonstrates the superiority of the new approach. By contrast, asymmetry parameters remain numerically unstable after introduction quantum corrections. The best of the assessed approximations, termed MDC(5), is recommended for routine application to large molecules with small-amplitude vibrations.