Dissipative Tunneling Rates through the Incorporation of First-Principles Electronic Friction in Instanton Rate Theory I: Theory

TL;DR

This paper introduces a new theoretical framework combining quantum nuclear effects and non-adiabatic electronic friction to accurately compute reaction rates on metallic surfaces, applicable to complex systems.

Contribution

It develops the RPI-EF method integrating electronic friction into instanton theory, enabling efficient first-principles calculations of reaction rates with non-adiabatic effects.

Findings

Derived general equations for spatial and frequency-dependent friction tensor

Connected RPI-EF with ab initio electronic friction formalism without additional approximations

Applicable to high-dimensional realistic systems involving metallic surfaces

Abstract

Reactions involving adsorbates on metallic surfaces and impurities in bulk metals are ubiquitous in a wide range of technological applications. The theoretical modelling of such reactions presents a formidable challenge for theory because nuclear quantum effects (NQEs) can play a prominent role and the coupling of the atomic motion with the electrons in the metal gives rise to important non-adiabatic effects (NAEs) that alter atomic dynamics. In this work, we derive a theoretical framework that captures both NQEs and NAEs and, due to its high efficiency, can be applied to first-principles calculations of reaction rates in high-dimensional realistic systems. In more detail, we develop a method that we coin ring polymer instanton with explicit friction (RPI-EF), starting from the ring-polymer instanton formalism applied to a system-bath model. We derive general equations that incorporate the spatial and frequency dependence of the friction tensor, and then combine this method with the \textit{ab initio} electronic friction formalism for the calculation of thermal reaction rates. We show that the connection between RPI-EF and the form of the electronic friction tensor presented in this work does not require any further approximations, and it is expected to be valid as long as the approximations of both underlying theories remain valid.