The estimation of the heat capacity of NpO2

Abstract

The heat capacity Cp, mof NpO2was estimated for temperatures between 300 K and 1400 K. The Cp, mwas evaluated as a sum of three terms, phonon vibration Cph, m, dilation Cd, m, and Schottky specific heat Cs, m. The Cph, mand Cd,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 Cp,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.