Molecular Dynamics Simulations of Warm Dense Carbon

• Published in: Contributions to plasma physics (1988) Vol. 55; no. 5; pp. 390 - 398
• Main Authors: Whitley, H. D., Sanchez, D. M., Hamel, S., Correa, A. A., Benedict, L. X.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.05.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Carbon; Classical molecular dynamics; Computer simulation; Coulomb friction; density functional molecular dynamics; equation of state; Inertial confinement fusion; Mathematical models; Molecular dynamics; Phases; Simulation
• ISSN: 0863-1042; 1521-3986
• DOI: 10.1002/ctpp.201400101

We present classical and DFT‐based molecular dynamics (MD) simulations of carbon in the warm dense matter regime (ϱ = 3.7 g/cc, 0.86 eV < T < 8.62 eV [T < 100 eV for classical MD]). Two different classical interatomic potentials are used: 1. LCBOP, designed to simulate condensed (e.g. solid) phases of C, and 2. linearly screened Coulomb (Yukawa) potentials. It is shown that LCBOP over‐predicts minima and maxima in the pair correlation functions of liquid‐C in this regime when compared to the DFT‐MD results. The screened Coulomb model, while under‐correlating at low‐T, seems to produce the correct qualitative features in the static ionic pair distributions at the highest‐T. However, both approaches predict the decay in the ionic contribution of the specific heat as T → ∞ to be much slower than that predicted by a model based on DFT‐MD. These differences in the MD‐derived equations of state in warm dense regimes could have important consequences when using classical inter‐ionic forces such as these in large‐scale MD simulations aimed at studying, for instance, processes of relevance to inertial confinement fusion when C is used as an ablator material. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)