CrAs: heat capacity, enthalpy increments, thermodynamic properties from 5 to 1280 K, and transitions

Abstract

The heat capacity of chromium arsenide has been measured by adiabatic calorimetry from 5 to 1050 K and enthalpy increments have been taken over the range 875 to 1280 K with respect to 298.15 K by drop calorimetry. The heat capacity shows a distinct bell-shaped transition with a peak at 259.9 K related to the disappearance of antiferromagnetic helical ordering on heating. The enthalpy and entropy of this transition are 177 calth mol-1 and 0.69 calth K-1 mol-1, respectively. At 1170 K another transition is observed related to the phase change from the MnP- to the NiAs-type structure. The enthalpy and entropy of the latter gradual transition are 280 calth mol-1 and 0.22 calth K-1 mol-1, respectively. Thermodynamic functions have been evaluated and the values of Cp, {So(T)-So(0)}, -{o(T)-Ho(0)}/T at 298.15 K are 12.501, 15.40, and 6.990 calth K-1 mol-1 and 16.09, 32.53, and 19.86 calth K-1 mol-1 at 1000 K.