Efficient Composite Infrared Spectroscopy: Combining the Doubly-Harmonic Approximation with Machine Learning Potentials

TL;DR

This paper presents a computationally efficient method for predicting gas-phase IR spectra of organic molecules by combining the doubly-harmonic approximation with machine learning potentials, improving accuracy and speed.

Contribution

It introduces a composite approach that integrates the doubly-harmonic approximation with machine learning potentials, enhancing IR spectra prediction accuracy and computational efficiency.

Findings

Machine learning potentials like MACE-OFF23 improve IR spectra prediction accuracy.

The proposed method offers a faster alternative to traditional quantum mechanical calculations.

Systematic testing identifies optimal protocols for efficient IR spectra computation.

Abstract

Vibrational spectroscopy is a cornerstone technique for molecular characterization and offers an ideal target for the computational investigation of molecular materials. Building on previous comprehensive assessments of efficient methods for infrared (IR) spectroscopy, this study investigates the predictive accuracy and computational efficiency of gas-phase IR spectra calculations, accessible through a combination of modern semiempirical quantum mechanical and transferable machine learning potentials. A composite approach for IR spectra prediction based on the doubly-harmonic approximation, utilizing harmonic vibrational frequencies in combination squared derivatives of the molecular dipole moment, is employed. This approach allows for methodical flexibility in the calculation of IR intensities from molecular dipoles and the corresponding vibrational modes. Various methods are systematically tested to suggest a suitable protocol with an emphasis on computational efficiency. Among these methods, semiempirical extended tight-binding (xTB) models, classical charge equilibrium models, and machine learning potentials trained for dipole moment prediction are assessed across a diverse dataset of organic molecules. We particularly focus on the recently reported machine learning potential MACE-OFF23 to address the accuracy limitations of conventional low-cost quantum mechanical and force-field methods. This study aims to establish a standard for the efficient computational prediction of IR spectra, facilitating the rapid and reliable identification of unknown compounds and advancing automated analytical workflows in chemistry.