Constant-volume specific heat of solid argon

Specific heats of solid argon were measured between 25 K and 120 K in a closed pressure vessel. Between 60 K and the melting point of 120 K the solid filled the vessel, and at the m.p. the pressure was 1.6 kbar. After correction for the nonrigidity of the container, we find thatCvincreases by 7.3% between 60 K and 120 K, reaching 2.8 R. Comparison with recent calculations based on self-consistent phonon theory reveals substantial discrepancies from the data, indicating the necessity of including higher-order terms in the theory.