Nanoscale heat transfer on the picosecond time scale

Using the method of molecular dynamics, we have examined the decay of an in stantaneously imposed heat pulse on an equilibrium model fluid similar to s uper-critical argon, The spatial extent of the initial pulse is quite small - on the order of 100 nm(3); the amount of energy added to the system is o nly 5% of the total system kinetic energy. This small pulse decays quite ra pidly, within several picoseconds, but the decay proceeds more slowly than predictions based on the hydrodynamic equations. During the first picosecon d of the decay, the kinetic energy is not equipartitioned and a very fast p rocess of energy transfer from kinetic energy to potential energy takes pla ce. A good fit to the molecular dynamics data is obtained using a simple li near superposition of the hydrodynamic and free streaming theories. (C) 200 1 Elsevier Science B.V. All rights reserved.