Algorithm for auto-generation of hindered internal rotation parameters for complex chemical systems

Abstract

In order to obtain accurate thermodynamic properties for a chemical species, an effective and rigorous improvement on the common harmonic oscillator approximation is to solve the 1-D Schrödinger equation for hindered internal rotors (HIRs), which requires detailed information about the rotors (e.g., low-frequency vibrational modes needed to be treated as hindered internal rotors and the corresponding rotational axes, groups, internal symmetries, and hindrance potentials). Such a treatment is tedious, prone-to-error even for experts; thus, it is challenging to make it a de-facto procedure for general cases. In this work, we present a robust JAVA-based algorithm for automatically generating the HIR parameters using data from the electronic structure calculations. The algorithm has been shown to be reliable via different types of test cases. As a result, when combined with a HIR engine such as that of MSMC (https://sites.google.com/site/msmccode), the scheme provides a powerful tool for calculating accurate thermodynamic data for a wide range of systems on-the-fly.