“…Some sets of model parameters used to fit low temperature heat capacity measurements are purely empirical (see, e.g., [ 1 , 2 , 3 , 4 ]), other parameters are at least partly motivated by theory, e.g., following the Debye–Einstein approach [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. A Debye–Einstein integral to describe heat capacities of several compounds is introduced by Kelley and King [ 5 ].…”