Isotope Effects in the Specific Heat of Solid Neon

Specific-heat measurements of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ are reported in the temperature range 2.5-23.5 K. The measurements were made simultaneously on the two isotopes in a calorimeter employing a mechanical heat switch. The results are presented in the form of tables of smoothed values of the following thermodynamic properties: specific heat at constant pressure, specific heat at constant volume, entropy, enthalpy, and the Grüneisen parameter. The results are compared with the Nernst-Lindemann equation, the Grüneisen equation of state, and the theoretical calculations of Barron, Gupta et al., Gillis et al., and Goldman et al., Excellent agreement is found at low temperatures between the present results and calculations based on anharmonic models. However, discrepancies arise at higher temperatures.