Uranium chalcogenides--II Heat capacities and thermodynamic properties of US2 and US3 from 5 to 350[deg]K

Abstract

Heat capacity measurements and calculations of thermodynamic properties have been carried out for the compounds US2 and US3 from 5 to 350[deg]K. The temperature dependence of the heat capacities is of normal sigmate type, except that for US2 the rise in heat capacity in the region 10 to 20[deg]K is more rapid than expected. Comparison of the US2 data with those on US and US3 indicates the presence of a Schottky-type transition in US2 with a maximum of about 0[middle dot]5 cal mole-1 [deg]K-1 at 25[deg]K.Values of the heat capacity (Cp), entropy (S[deg] - S[deg]0), and Gibbs energy function [-(G[deg] - G[deg]0)/T] at 298[middle dot]15[deg]K are 17[middle dot]86, 26[middle dot]42, and 14[middle dot]01 for US2 and 22[middle dot]85, 33[middle dot]09, and 17[middle dot]45 for US3, respectively, in cal mole-1[deg]K-1.