Heat capacity anomalies associated with phase transition type change in CeH2+c-like superstoichiometric rare-earth dihydrides Original Research Article

In a number of superstoichiometric rare-earth dihydrides RH2+c, the subsystem of octa-hydrogen atoms undergoes an order–disorder phase transition. Previously it was shown that in CeH2+c, a phase transition type change occurs at some concentration c0: the structural transformation, discontinuous for cc0. In the present article, the temperature dependence of the ordering subsystem heat capacity C(T) is calculated in a wide range of concentrations c and it is shown that the discontinuity of C(T) at the structural transformation point Ttr, ΔC(Ttr), becomes extremely large when c∼c0. The obtained results are analyzed from the point of view of previous theoretical considerations and compared with the available experimental data.