Performance of a black-box-type rovibrational method in comparison with a tailor-made approach: case study for the methane-water dimer

TL;DR

This study compares a general black-box rovibrational method with a specialized approach for the methane-water dimer, demonstrating comparable accuracy with larger basis sets, thus validating the black-box method's effectiveness.

Contribution

It shows that a general black-box rovibrational method can achieve near the performance of a specialized, tailor-made approach for floppy molecular dimers.

Findings

Black-box method approaches tailor-made accuracy with larger basis sets.

Excellent numerical agreement between the two methods.

Black-box method is effective for floppy dimers like methane-water.

Abstract

The present work intends to join and respond to the excellent and thoroughly documented rovibrational study of [X.-G. Wang and T. Carrington, Jr., J. Chem. Phys. 154, 124112 (2021)] that used an approach tailored for floppy dimers with an analytic dimer Hamiltonian and a non-product basis set including Wigner $D$ functions. It is shown in the present work that the GENIUSH black-box-type rovibrational method can approach the performance of the tailor-made computation for the example of the floppy methane-water dimer. Rovibrational transition energies and intensities are obtained in the black-box-type computation with `only' 2-3 times larger basis set sizes and in an excellent numerical agreement in comparison with the more efficient tailor-made approach.