Anharmonic effects in the heat capacity of Al

The vibrational heat capacity of aluminum at fixed volume is studied in molecular dynamics and Monte Carlo simulations, using effective interactions due to Ercolessi and Adams, Mishin , and Mei and Davenport. When experimental data are reduced to represent the classical vibrational heat capacity at fixed volume, the result is within about +/-2 % of 3k(B)/atom up to the melting temperature of Al, thus suggesting small anharmonic effects. Our simulations of the heat capacity are in good agreement with experiments, but also show that anharmonic effects are in fact large, with a cancellation between the low-order linear term in the temperature T and higher-order terms.