A generalized heat flow algorithm

Multiple nonequilibrium steady states for one-dimensional heat flow

A nonequilibrium molecular dynamics model of heat flow in one-dimensional lattices is shown to have multiple steady states for any fixed heat field strength f(e) ranging from zero to a certain positive value. We demonstrate that, depending on the initial conditions, there are at least two possibilities for the system's evolution: (i) formation of a stable traveling wave (soliton), and (ii) chaotic motion throughout the entire simulation. The percentage of the soliton-generating trajectories is zero for small field strength f(e), but increases sharply to unity over a critical region of the parameter f(e).

Unusually high thermal conductivity of carbon nanotubes

Combining equilibrium and nonequilibrium molecular dynamics simulations with accurate carbon potentials, we determine the thermal conductivity lambda of carbon nanotubes and its dependence on temperature. Our results suggest an unusually high value, lambda approximately 6600 W/m K, for an isolated (10,10) nanotube at room temperature, comparable to the thermal conductivity of a hypothetical isolated graphene monolayer or diamond. Our results suggest that these high values of lambda are associated with the large phonon mean free paths in these systems; substantially lower values are predicted and observed for the basal plane of bulk graphite.

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 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.