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Citation: Z.G. Fthenakis, I.D. Petsalakis, V. Tozzini, and N.N. Lathiotakis (2022), "Evaluating the performance of ReaxFF potentials for sp2 carbon systems (graphene, carbon nanotubes, fullerenes) and a new ReaxFF potential", Frontiers in Chemistry, 10, 951261. DOI: 10.3389/fchem.2022.951261.
Abstract: We study the performance of eleven reactive force fields (ReaxFF), which can be used to study sp2 carbon systems. Among them a new hybrid ReaxFF is proposed combining two others and introducing two different types of C atoms. The advantages of that potential are discussed. We analyze the behavior of ReaxFFs with respect to 1) the structural and mechanical properties of graphene, its response to strain and phonon dispersion relation; 2) the energetics of (n, 0) and (n, n) carbon nanotubes (CNTs), their mechanical properties and response to strain up to fracture; 3) the energetics of the icosahedral C60 fullerene and the 40 C40 fullerene isomers. Seven of them provide not very realistic predictions for graphene, which made us focusing on the remaining, which provide reasonable results for 1) the structure, energy and phonon band structure of graphene, 2) the energetics of CNTs versus their diameter and 3) the energy of C60 and the trend of the energy of the C40 fullerene isomers versus their pentagon adjacencies, in accordance with density functional theory (DFT) calculations and/or experimental data. Moreover, the predicted fracture strain, ultimate tensile strength and strain values of CNTs are inside the range of experimental values, although overestimated with respect to DFT. However, they underestimate the Young’s modulus, overestimate the Poisson’s ratio of both graphene and CNTs and they display anomalous behavior of the stress - strain and Poisson’s ratio - strain curves, whose origin needs further investigation.

Notes: The potential belongs to the type of Reax potentials, which is designed to describe interactions between condensed carbon phases (like graphene, diamond etc) and molecules composed of C, H, O and/or N atoms. It is a hybrid potential combining two other Reax potentials, namely the C-2013 potential (Srinivasan, S. G., van Duin, A. C. T., and Ganesh, P., J. Phys. Chem. A 119, 571–580 (2015)) for carbon condensed phases and RDX potential (Strachan, A., van Duin, A. C. T., Chakraborty, D., Dasgupta, S., and Goddard, W. A., Phys. Rev. Lett. 91, 098301 (2003)) for interactions between C/H/O/N atoms and molecules composed of C/H/O/N atoms, originally designed to describe initial chemical events in nitramine RDX explosions. The potential considers a hypothetical new species denoted as Cg, representing the carbon atoms in condensed carbon phases, and C, representing the carbon atoms in all other cases. The interactions between C/H/O/N atoms are described by the RDX potential, while the interactions between Cg-Cg atoms are described by a slightly modified C-2013 potential. Moreover, the interactions between Cg-C, Cg-H, Cg-O and Cg-N are also described by RDX potential, as if Cg was a C atom. The modification of GR-RDX-2021 potential with respect to the C-2013 for the Cg-Cg interactions has to do with the 39 general parameters of the potential, which has been chosen to be the parameters of the RDX potential.

See Computed Properties
Notes: These files were provided by Zacharias Fthenakis on Nov 3, 2022. "in.graphene" and "data.graphene_H_C_O_N" provide an example LAMMPS script and corresponding atomic configuration.
Date Created: October 5, 2010 | Last updated: November 18, 2022