Tight-Binding Molecular Dynamics of Shock Waves in Methane

The behavior of shock-compressed methane at high temperatures and pressures is studied using nonequilibrium molecular dynamics and linear-scaling tight-binding electronic structure theory in simulations containing as many as 1728 molecules. For certain piston velocities, a chemical dissociation wave evolves that lags behind the compressive shock front. At about 1thinspthinspps, the dissociation region consists mainly of molecular hydrogen and hydrocarbon polymers. Shock wave experiments, which access much longer time scales, suggest that the hydrocarbons ultimately decompose into elemental carbon. {copyright} {ital 1999} {ital The American Physical Society}