Theoretical approach to the nanoporous phase diagram of carbon

Abstract

Nanoporous carbon has been extensively used in a wide range of applications ranging from water treatment to electrochemical applications, such as in energy storage devices. An effort to relate structural to thermodynamical properties has not been explored from an atomistic approach. In this work we present numerical strategies to produce and study nanoporous carbon structures, using molecular dynamics simulations and a many-body potential. We designed a heating-quenching procedure in a thermodynamic region bounded by the critical, and triple point densities of carbon to study an ensemble of 1750 atomic arrangements produced at different densities, quench rates, and using graphite and diamond unit cells as precursor structures. All these samples were numerically characterized through the calculation of the free volumes, surface areas, radial distribution functions, and structure factors. We found particularly useful the potential energy dependence with $sp^3$ hybridization content, to determine structural phases through clustering methods. Three phases were related to graphite-like, sponge-like, and unstable states. We showed that our results are compatible with available experiments and different theoretical schemes, concluding that the use of Tersoff potential is a reliable choice to produce nanoporous structures with low computational cost.