High temperature enthalpy increments and thermodynamic functions of ZrCo: An experimental and theoretical study

• Enthalpy increment study of Zr0.5Co0.5 carried out using inverse drop calorimeter.
• H(T)–H(298.15 K) and Cp of ZrCo obtained as a function of temperature.
• Thermodynamics functions of ZrCo were also obtained.
• Ab-initio study performed to support the experimental results.

The thermodynamic properties of ZrCo intermetallic were investigated both experimentally and theoretically to determine its applicability for the storage of hydrogen isotopes. The enthalpy increments of ZrCo were measured using a high temperature inverse drop calorimeter in the temperature range 642–1497 K. The enthalpy increments and heat capacity obtained for Zr0.5Co0.5(s) in the temperature range 642–1497 K were fitted into following polynomial expressions:Hm0(T)−Hm0(298.15   K)(J·mol−1)=25.682·(TK)+29.807·10−4·(TK)2+2.1864·105·(KT)−8655.5Cp.m0(J·K−1·mol−1)=25.682+5.961·10−3·(TK)−2.1864·105·(KT)2The enthalpy of formation of ZrCo(s) at 298.15 K was calculated to be −55.96 kJ mol−1 using the ab-initio   method. The temperature dependent thermodynamic functions were calculated from the Debye–Grüneisen quasi-harmonic approximation. A set of thermodynamic functions for ZrCo alloy were also calculated using experimental heat capacity data obtained in this study. The theoretically calculated low temperature heat capacity (Cp,m0) and entropy (Sm0) values of ZrCo smoothly joined with that of experimental high temperature data.