Vibrational infrared and Raman spectrum of HCOOH from variational computations

TL;DR

This study computes the vibrational spectra of formic acid using advanced variational methods and ab initio data, providing detailed energies and transition moments for comparison with experimental spectra.

Contribution

It introduces a full-dimensional variational approach with high-level ab initio surfaces to accurately compute vibrational energies and spectra of HCOOH.

Findings

Vibrational energies converged up to 4500 cm$^{-1}$

Simulated infrared and Raman spectra match experimental data

Provides benchmark vibrational transition moments and wave functions

Abstract

All vibrational energies of the (trans-, cis-, delocalized-) formic acid molecule are converged up to 4500 cm$^{-1}$ beyond the zero-point vibrational energy with the GENIUSH-Smolyak variational approach and using an ab initio potential energy surface [D. P. Tew and W. Mizukami, J. Phys. Chem. A, 120, 9815-9828 (2016)]. Full-dimensional dipole and polarizability surfaces are fitted to points computed at the CCSD/aug-cc-pVTZ level of theory. Then, body-fixed vibrational dipole and polarizability transition moments are evaluated and used to simulate jet-cooled infrared and Raman spectra of HCOOH. The benchmark-quality vibrational energy, transition moment, and wave function list will be used in further work in comparison with vibrational experiments, and in further rovibrational computations.