Mechanical Vibrational Relaxation of NO Scattering from Metal and Insulator Surfaces: When and Why Are They Different?

TL;DR

This study uses neural network potentials to compare vibrational relaxation of NO molecules on metal and insulator surfaces, revealing mechanical energy transfer mechanisms influenced by initial states and potential landscapes.

Contribution

It introduces a computational approach to explain vibrational energy transfer differences between metallic and insulating surfaces beyond electronic effects.

Findings

Vibrational energy transfers to substrate phonons on Au(111).

Energy transfer is limited in NO/LiF(001) due to repulsive interactions.

Initial vibrational state and potential landscape jointly affect energy transfer.

Abstract

NO scattering from metallic and insulating surfaces represent contrasting benchmark systems for understanding energy transfer at gas-surface interface. Strikingly different behaviors of highly vibrationally excited NO scattered from Au(111) and LiF(001) were observed and attributed to disparate electronic structures between metals and insulators. Here, we reveal an alternative mechanical origin of this discrepancy by comparative molecular dynamics simulations with globally accurate adiabatic neural network potentials of both systems. We find that highly-vibrating NO can reach for the high dissociation barrier on Au(111), by which vibrational energy can largely transfer to translation/rotation and further dissipate into substrate phonons. This mechanical energy transfer channel is forbidden in the purely repulsive NO/LiF(001) system or for low-vibrating NO on Au(111), where molecular vibration is barely coupled to other degrees of freedom. Our results emphasize that the initial state and potential energy landscape concurrently influence the mechanical energy transfer dynamics of gas-surface scattering.