Solitary waves in nonequilibrium molecular dynamics simulations of heat flow in one-dimensional lattices

We study the use of the Evans Nonequilibrium Molecular Dynamics (NEMD) heat flow algorithm for the computation of the heat conductivity in one-dimensional lattices. For the well-known Fermi-Pasta-Ulam (FPU) model, it is shown that when the heat field strength is greater than a certain critical value (which depends on the system size) solitons can be generated in molecular dynamics simulations starting from random initial conditions. Such solitons are stable and travel with supersonic speeds. For smaller heat fields, no solitons are generated in the molecular dynamics simulations; the heat conductivity obtained via the NEMD algorithm increases monotonically with the size of the system.