, where E hot and E cold are the cumulative energies added and subtracted from the atoms in the hot and cold regions during the NEMD simulation respectively, t is the time over which the simulation proceeded and A is the cross sectional area of the simulation box in the xy plane. ⟨ Ė⟩ was determined by the gradient of the energy exchanged in the hot and cold thermostats against time. The thermal conductivity of the fluid was then calculated using Fourier's law: