CLASSICAL SPECIFIC-HEAT OF AN ATOMIC LATTICE AT LOW-TEMPERATURE, REVISITED

We present results of a standard (constant energy) molecular dynamics simulation of a Lennard-Jones lattice at low temperature. The kinetic energy fluctuations exhibit an anomalous behavior, due to a dynamics w hich is only weakly chaotic. Such a dynamics does not allow the use of the usual microcanonical equilibrium formula to compute the specific heat. We devise a different method for computing the specific heat, wh ich exploits just the weak chaos at low temperature. The result is tha t at low temperature this ''revisited'' specific heat is lower than th e classical value, and approaches zero when the temperature goes to ze ro. Only for exceedingly long trajectories does the specific heat appr oach the classical value, with the exception of the very low temperatu re range. These results prompt a reconsideration, in the frame of mode rn nonlinear dynamics, of early intuitions by Nernst and Jeans.