Since the invocation of the concept of apparently characteristic, material-specific temperature parameters, [THETA], within Debye's classical paper [1] on specific heats of solids, one was concerned with a large variety of quotations of corresponding [[THETA].sub.D] values (so-called "Debye temperatures") within numerous thermophysical research papers, including various representative review articles [2-5] and books [6-10].

where the upper limits of integration are given by the ratios, [x.sub.D] (T) = [[THETA].sub.D] (T)/T, of adjustable Debye temperatures versus the respective lattice temperatures and [C.sub.Vh] ([infinity]) represents the familiar Dulong-Petit limiting value for the isochoric lattice heat capacity in harmonic approximation (i.e., in particular [C.sub.Vh] ([infinity]) = 6R, for binary materials).

In the course of numerical fittings of measured (isobaric) heat capacities, [C.sub.p] (T), on the basis of (1), it has continually been found that, in contrast with Debye's original suggestion [1], proper simulations of such heat capacity curves can in fact be realized only by admitting rather strong T-dependencies of the material-specific Debye temperatures, [[THETA].sub.D] (T).

Globally one can thus assess that Debye's original idea, according to which heat capacities of solids might be represented by Debye function integrals (of type (1)), whose upper limits of integration should be based on fixed, material-specific [[THETA].sub.D] values, is largely illusionary.

Such drastic deviations of physically realistic PDOS spectra from Debye's naive (quadratic) PDOS model function [1], [g.sub.D] (e) [varies] [[epsilon].sup.2], are continually confirmed to be indeed the main cause of the obviously typical, nonmonotonic (non-Debye) behaviours of [[THETA].sub.D](T) curves.

Considerably more problematic and difficult, however, is a proper computational solution of the hitherto largely ignored inverse problem, namely, the reliable determination of effective Debye temperatures, [[THETA].sub.D](T), on the basis of measured heat capacities, [C.sub.p] (T).

Concerning the successive development of this novel analytical apparatus for Debye temperatures, we would still like to note that some partial results in form of asymptotic (approximate) Debye temperature expressions had already been published in two preceding papers, namely, in [13] for the low-temperature region (T < [[THETA].sub.D](T)/12),

In Section 5 we perform, on the basis of a couple of precision formulas derived in Appendix B, transformations of the experimental heat capacity data in question (including the corresponding theoretical [C.sub.p] (T) and [C.sub.Vh] (T) curves), into the respective Debye temperature representations.

where the [[kappa].sub.Ck] ([x.sub.1] (T)) functions (being due to the two continuous components, [varies] [[epsilon].sup.2k], in (7)) are given in form of integrals of Debye and non-Debye type [14, 21]

the ratio of the characteristic phonon temperature associated with the first (lowest) special point, [[THETA].sub.1], versus lattice temperature, T (in analogy with the notation used within Debye's theory, [x.sub.D](T) [equivalent to] [[THETA].sub.D] /T; cf.