Direct computation of the quantum partition function by path-integral nested sampling

TL;DR

This paper introduces a novel computational method combining path-integral formalism with nested sampling to calculate the quantum partition function, offering an efficient alternative for medium-sized molecules at higher temperatures.

Contribution

The work presents the first application of path-integral nested sampling for computing the quantum partition function, demonstrating its effectiveness for small molecules of spectroscopic interest.

Findings

Method is applicable to small molecules with spectroscopic relevance.

Computational cost depends on potential-energy surface evaluation time.

Potentially more efficient than traditional Boltzmann summation for medium-sized molecules.

Abstract

In the present work we introduce a computational approach to the absolute rovibrational quantum partition function using the path-integral formalism of quantum mechanics in combination with the nested sampling technique. The numerical applicability of path-integral nested sampling is demonstrated for small molecules of spectroscopic interest. The computational cost of the method is determined by the evaluation time of a point on the potential-energy surface (PES). For efficient PES implementations, the path-integral nested-sampling method can be a viable alternative to the direct Boltzmann summation technique of variationally computed rovibrational energies, especially for medium-sized molecules and at elevated temperatures.