Degree of metallicity and thermodynamic conditions of superconducting transition appearance. Temperature effect

Physicochemical conditions are analyzed for occurrence of extremum on temperature dependence of metallicity for simple elements and compounds. Correspondence with two extremum types dμ(T)/dT=0(1) and aμ(T)/dT=∞(2) is shown to be either for relationship between ion radii of all components (1) or for charge compensation on the fraction of atoms (2). The condition 1 can be accomplished in superconducting metals and intermetallics, and condition 2 - in oxide high temperature superconductors. A number of intermetallic compounds is under consideration (Nb3Ge, AuBe, Mo3Ir etc)