Calorimetric study of MgZn2 and Mg2Zn11

Abstract

Abstract The thermodynamic properties of MgZn2 and Mg2Zn11 were investigated by calorimetry. The standard entropies of formation at 298 K, Δ f S 298 ° $\Delta _{\rm{f}} S_{298}^{\rm{^\circ }} $ were determined from measuring the heat capacities, Cp , from near absolute zero (2 K) to 390 K by the relaxation method. The standard enthalpies of formation at 298 K, Δ f H 298 ° $\Delta _{\rm{f}} H_{298}^{\rm{^\circ }} $ were determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energies of formation at 298 K, Δ f G 298 ° $\Delta _{\rm{f}} G_{298}^{\rm{^\circ }} $ were determined from these data. The electronic contribution to the heat capacities of MgZn2 and M2Zn11 were found to be similar to pure Zn, indicating that the valence electrons of Mg are trapped by the density of states for Zn in the vicinity of the Fermi level.