Young's moduli of carbon materials investigated by various classical molecular dynamics schemes

TL;DR

This study uses classical molecular dynamics with various potentials to evaluate the Young's moduli of different carbon materials, comparing results to experimental data to assess the accuracy of these computational models.

Contribution

It systematically compares classical potentials' predictions of Young's moduli for carbon materials, highlighting their limitations and suitability for different observables.

Findings

Young's moduli vary significantly with different potentials.

Classical potentials can approximate bond lengths but differ in mechanical property predictions.

Careful selection of potentials is necessary for accurate mechanical property estimation.

Abstract

Classical carbon potentials together with classical molecular dynamics are employed to calculate structures and physical properties of such carbon-based materials where quantum mechanical methods fail either due to the excessive size, irregular structure or long-time dynamics. Examples are given by recently synthesized free-standing carbon nanomembranes (CNM) with molecular thickness and macroscopic lateral size as well as by amorphous carbon. Although such potentials, as for instance implemented in LAMMPS, yield reasonably accurate bond lengths and angles for several carbon materials such as graphene, it is not clear how accurate they are in terms of mechanical properties such as Young's moduli. We performed large-scale classical molecular dynamics investigations of three carbon-based materials using the various potentials implemented in LAMMPS as well as the highly sophisticated EDIP potential of Nigel Marks. We demonstrate how the Young's moduli vary with classical potentials and compare to experimental results. Since classical descriptions of carbon are bound to be approximations it is not astonishing that different realizations yield differing results. One should therefore carefully check for which observables a certain potential is suited. We hope to contribute to such a clarification.