The estimation of the heat capacity of NpO2

The heat capacity C-p,C-m of NpO2 was estimated for temperatures between 30 0 K and 1400 K. The C-p,C-m was evaluated as a sum of three terms, phonon v ibration C-ph,C-m, dilation C-d,C-m, and Schottky specific heat C-s,C-m. Th e C-ph,C-m and C-d,C-m were calculated using the Debye temperature, Gruneis en constant and thermal expansion data obtained by high-temperature X-ray d iffractometry. The coefficient of the linear thermal expansion (l.t.e.) for NPO2 was given as a polynomial function up to T = 1573 K. The estimated C- p,C-m was 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. (C) 2001 Academic Press .