Reappraising 1907 Einstein’s Model of Specific Heat

This article emphasizes that the Einstein and Debye models of specific heats of solids are correlated more tightly than currently acknowledged. This correlation is evidenced without need of additional hypotheses on the early Einstein model. The results are also extensible to the case of a system of fermions; as an example, the specific heat of the electron sea in metals is inferred in the frame of the proposed approach only.