Melt Curves of RDX and HMX Computed by Molecular Simulation

ORAL

Abstract

In this talk, we show how the solid–liquid coexistence curves of classical fully flexible atomistic models of α-RDX and β-HMX can be calculated using thermodynamically rigorous methodologies that identify where the free energy difference between the phases is zero. The free energy difference between each phase at a given state point was computed using the pseudosupercritical path (PSCP) method, and Gibbs–Helmholtz integration was used to evaluate the solid–liquid free energy difference as a function of temperature. This procedure was repeated for several pressures to determine points along the coexistence curve. While effective, this method is computationally expensive. To trace out the coexistence curve in a more computationally economical manner, Gibbs–Duhem integration was used starting from a coexistence point determined by the PSCP method. For α-RDX, the predicted melting temperature increases significantly more for a given increase in pressure when compared to available experimental data.

*This work was supported in part by high-performance computer time and resources from the DOD High Performance Computing Modernization Program (HPCMP). Research was sponsored by the Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF-21-2-0177 and by the 2020 CCDC-ARL Summer Student Experience sponsored by the HPCMP's High Performance Computing Internship Program under Project Number HIP-20-021. Research performed by ML was sponsored by the Army Research Office, and was accomplished under Cooperative Agreement Number W911NF-20-2-0203.

–

Publication: Garrett M. Tow, James P. Larentzos, Michael S. Sellers, Martin Lísal, and John K. Brennan, "Predicting Melt Curves of Energetic Materials Using Molecular Models," Propellants, Explosives, Pyrotechnics, accepted.

Presenters

  • Garrett M Tow

    • Weapons and Materials Research Directorate, U.S. Army DEVCOM Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA
    • Army Research Laboratory, Adelphi, MD
    • U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory, Aberdeen Proving Ground, MD, United States
    • U.S. Army Research Laboratory

Authors

  • Garrett M Tow

    • Weapons and Materials Research Directorate, U.S. Army DEVCOM Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA
    • Army Research Laboratory, Adelphi, MD
    • U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory, Aberdeen Proving Ground, MD, United States
    • U.S. Army Research Laboratory

  • James P Larentzos

    • Weapons and Materials Research Directorate, U.S. Army DEVCOM Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA
    • U.S. Army Research Laboratory
    • Army research Laboratory, Adelphi, MD
    • U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory, Aberdeen Proving Ground, MD, United States

  • Michael S Sellers

    • Booz Allen Hamilton Inc., McLean, VA 22102, USA

  • Martin Lίsal

    • Department of Physics, Faculty of Science, Jan Evangelista Purkyně University in Ústí nad Labem, Ústí n. Lab. 400 96, Czech Republic

  • John K Brennan

    • Weapons and Materials Research Directorate, U.S. Army DEVCOM Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA
    • U.S. Army Research Laboratory
    • U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory, Aberdeen Proving Ground, MD, United States