title: Simulations of shocked methane including self-consistent semiclassical quantum nuclear effects.
abstract: A methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects on the fly. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift.
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Tingting
authors.initials: T
authors.lastname: Qi
authors.forename: Evan J
authors.initials: EJ
authors.lastname: Reed
mesh_terms: D008697:Methane / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D013696:Temperature
chemical_list: D008697:Methane