Accuracy and limitations of the bond polarizability model in modeling of Raman scattering from molecular dynamics simulations

TL;DR

This study evaluates the bond polarizability model's effectiveness in simulating Raman spectra from molecular dynamics, revealing its accuracy for peak shifts but limitations in complex or asymmetric systems.

Contribution

It systematically assesses the accuracy and limitations of the bond polarizability model for both molecular and solid-state systems using DFT-parameterized data.

Findings

BPM reliably reproduces peak position shifts in Raman spectra.

Limitations arise in asymmetric systems due to the non-interacting bonds assumption.

Qualitative inaccuracies occur in systems with large deviations from ground state structures.

Abstract

Calculation of Raman scattering from molecular dynamics (MD) simulations requires accurate modeling of the evolution of the electronic polarizability of the system along its MD trajectory. For large systems, this necessitates the use of atomistic models to represent the dependence of electronic polarizability on atomic coordinates. The bond polarizability model (BPM) is the simplest such model and has been used for modeling the Raman spectra of molecular systems but has not been applied to solid-state systems. Here, we systematically investigate the accuracy and limitations of the BPM parameterized from density functional theory (DFT) results for a series of simple molecules such as CO2, SO2, H2S, H2O, NH3, and CH4, the more complex CH2O, CH3OH and CH3CH2OH and thiophene molecules and the BaTiO3 and CsPbBr3 perovskite solids. We find that BPM can reliably reproduce the overall features of the Raman spectra such as shifts of peak positions. However, with the exception of highly symmetric systems, the assumption of non-interacting bonds limits the quantitative accuracy of the BPM; this assumption also leads to qualitatively inaccurate polarizability evolution and Raman spectra for systems where large deviations from the ground state structure are present.