The estimation of the heat capacity of NpO2

The heat capacity C_{p, m}of NpO₂was estimated for temperatures between 300 K and 1400 K. The C_{p, m}was evaluated as a sum of three terms, phonon vibration C_{ph, m}, dilation C_{d, m}, and Schottky specific heat C_{s, m}. The C_{ph, m}and C_d,mwere calculated using the Debye temperature, Grüneisen constant and thermal expansion data obtained by high-temperature X-ray diffractometry. The coefficient of the linear thermal expansion (l.t.e.) for NpO₂was given as a polynomial function up to T =  1573 K. The estimated C_p,mwas compared with that of previous studies. The present result at T =  300 K was 66.87 J · K ^− 1· mol ^− 1, which agreed well with previous results, 66.22 J · K ^− 1· mol ^− 1, measured by using calorimetry. The thermodynamic functions were given as a function of temperature.