A semiclassical hybrid approach to linear response functions for infrared spectroscopy

TL;DR

This paper introduces a hybrid semiclassical method for calculating infrared spectroscopy response functions, reducing computational effort while maintaining accuracy, especially for systems with few degrees of freedom.

Contribution

It presents a novel hybrid approach based on the Herman-Kluk propagator that simplifies calculations of linear response functions at high temperatures.

Findings

Significant reduction in computational effort for small systems.

Effective approximation for coupled anharmonic oscillators.

Maintains accuracy with fewer degrees of freedom.

Abstract

Based on the integral representation of the semiclassical propagator of Herman and Kluk (HK), and in the limit of high temperatures, we formulate a hybrid expression for the correlation function of infrared spectroscopy. This is achieved by performing a partial linearization inside the integral over the difference of phase space variables that occurs after a twofold application of the HK propagator. A numerical case study for a coupled anharmonic oscillator shows that already for a total number of only two degrees of freedom, one of which is treated in the simplified manner, a substantial reduction of the numerical effort is achieved.