The random force in molecular dynamics with electronic friction

Nils Hertl; Raidel Martin-Barrios; Oihana Galparsoro; Pascal Larregaray; Daniel J. Auerbach; Dirk Schwarzer; Alec M. Wodtke; Alexander Kandratsenka

arXiv · 2103.03005

The random force in molecular dynamics with electronic friction

Nils Hertl·Raidel Martin-Barrios·Oihana Galparsoro·Pascal Larregaray·Daniel J. Auerbach·Dirk Schwarzer·Alec M. Wodtke·Alexander Kandratsenka

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Abstract

The Langevin equation includes a random force to maintain equilibrium and prevent friction from bringing motion to a standstill; but for ballistic motion, the random force is often neglected. Here, we use the Langevin equation for molecular dynamics simulations of 2.76 eV H-atoms experiencing electronic friction in collisions with 300 K metals, where a random force arises from thermal electron-hole pairs. Simulations without the random force fail dramatically to reproduce experiment, although the incidence energy is much larger than $k_\text{B}T$. We analyze the Ornstein-Uhlenbeck process to show that this is a general property of ballistic particles experiencing friction under the influence of thermal fluctuations.

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Nils Hertl, Raidel Martin-Barrios, Oihana Galparsoro, Pascal Larregaray, Daniel J. Auerbach, Dirk Schwarzer, Alec M. Wodtke, Alexander Kandratsenka. 2021-03-04. The random force in molecular dynamics with electronic friction. https://arxiv.org/abs/2103.03005

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