“…At room temperature, the heat capacities are 77.72, 72.61, 69.67, 59.33 and 48.27 J/mol K with the increasing x, respectively. It is known that for solids the difference between C p and C v is negligible at low temperatures, our calculated value of C v is smaller than the experimental data of C p ¼40.45 J/mol K in [51] for ZnO, while, our calculated value of C v for BeO is in fairly good agreement with the experimental C v values and 40.18 J/mol K in [52] at room temperature.…”