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 tigh t-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 1 ps, the d issociation region consists mainly of molecular hydrogen and hydrocarbon po lymers. Shock wave experiments, which access much longer time scales, sugge st that the hydrocarbons ultimately decompose into elemental carbon.