Reaction and relaxation at surface hotspots: using molecular dynamics and the energy-grained master equation to describe diamond etching.
The extent to which vibrational energy transfer dynamics can impact reaction outcomes beyond the gas phase remains an active research question. Molecular dynamics (MD) simulations are the method of choice for investigating such questions; however, they can be extremely expensive, and therefore it is worth developing cheaper models that are capable of furnishing reasonable results. This paper has two primary aims. First, we investigate the competition between energy relaxation and reaction at 'hotspots' that form on the surface of diamond during the chemical vapour deposition process. To explore this, we developed an efficient reactive potential energy surface by fitting an empirical valence bond model to higher-levelab initioelectronic structure theory. We then ran 160 000 NVE trajectories on a large slab of diamond, and the results are in reasonable agreement with experiment: they suggest that energy dissipation from surface hotspots is complete within a few hundred femtoseconds, but that a small fraction of CH3does in fact undergo dissociation prior to the onset of thermal equilibrium. Second, we developed and tested a general procedure to formulate and solve the energy-grained master equation (EGME) for surface chemistry problems. The procedure we outline splits the diamond slab into system and bath components, and then evaluates microcanonical transition-state theory rate coefficients in the configuration space of the system atoms. Energy transfer from the system to the bath is estimated using linear response theory from a single long MD trajectory, and used to parametrize an energy transfer function which can be input into the EGME. Despite the number of approximations involved, the surface EGME results are in reasonable agreement with the NVE MD simulations, but considerably cheaper. The results are encouraging, because they offer a computationally tractable strategy for investigating non-equilibrium reaction dynamics at surfaces for a broader range of systems.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK glowacki@bristol.ac.uk.|Department of Computer Science, University of Bristol, Bristol BS8 1UB, UK.|Department of Mechanical Engineering, Stanford University, 452 Escondido Mall, Stanford, CA 94305, USA.
David R
http://orcid.org/0000-0002-9608-3845
DR
Glowacki
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
W J
WJ
Rodgers
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.|Department of Mechanical Engineering, Stanford University, 452 Escondido Mall, Stanford, CA 94305, USA.
Robin
R
Shannon
Dassault Systémes BIOVIA, 334 Cambridge Science Park, Cambridge CB4 0WN, UK.
Struan H
SH
Robertson
Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium.
Jeremy N
JN
Harvey
chemical vapour deposition; diamond; heterogeneous chemistry; molecular dynamics; reaction dynamics; statistical mechanics