An interatomic potential for saturated hydrocarbons based on the modified embedded-atom method

TL;DR

This paper introduces a modified embedded-atom method (MEAM) interatomic potential tailored for saturated hydrocarbons, demonstrating its accuracy and applicability in modeling molecular geometries, energies, and PVT data, comparable to or better than existing reactive potentials.

Contribution

The work extends the MEAM formalism to covalently bonded saturated hydrocarbons, providing a new reactive potential with validated accuracy for hydrocarbons and related polymers.

Findings

MEAM accurately reproduces experimental and FP data for hydrocarbons.

The potential predicts PVT data of methane and other alkanes well.

MEAM shows promise for modeling covalent molecular systems.

Abstract

In this work, we developed an interatomic potential for saturated hydrocarbons using the modified embedded-atom method (MEAM), a reactive semi-empirical many-body potential based on density functional theory and pair potentials. We parameterized the potential by fitting to a large experimental and first-principles (FP) database consisting of 1) bond distances, bond angles, and atomization energies at 0 K of a homologous series of alkanes and their select isomers from methane to n-octane, 2) the potential energy curves of H$_2$, CH, and C$_2$ diatomics, 3) the potential energy curves of hydrogen, methane, ethane, and propane dimers, i.e., (H$_2$)$_2$, (CH$_4$)$_2$, (C$_2$H$_6$)$_2$, and (C$_3$H$_8$)$_2$, respectively, and 5) pressure-volume-temperature (PVT) data of a dense high-pressure methane system with the density of 0.5534 g/cc. We compared the atomization energies and geometries of a range of linear alkanes, cycloalkanes, and free radicals calculated from the MEAM potential to those calculated by other commonly used reactive potentials for hydrocarbons, i.e., second-generation reactive empirical bond order (REBO) and reactive force field (ReaxFF). MEAM reproduced the experimental and/or FP data with accuracy comparable to or better than REBO or ReaxFF. The experimental PVT data for a relatively large series of methane, ethane, propane, and butane systems with different densities were predicted reasonably well by MEAM. Although the MEAM formalism has been applied to atomic systems with predominantly metallic bonding in the past, the current work demonstrates the promising extension of the MEAM potential to covalently bonded molecular systems, specifically saturated hydrocarbons and saturated hydrocarbon-based polymers.