Bose-Einstein Condensation Picture of Superconductivity in Ag2 (Ag3Pb2H2O6), Na0.05WO3 and Na0.041NH3 composites. (Dilute metals)

Original · EN

Traditionally, when one describes the crystallographic structure of oxides, the oxygen ion radius r02 is assumed to be approximately equal to 1.4A. The oxygen ions occupy in this case 80-90% of the crystal volume. Metal atoms are considered then as ions playing a role of donors with rather small radius of (0.5 - 0.8) A. However, the atomic packing picture and, therefore, physical properties such as electric conductivity and superconductivity of oxides will be essentially different, if we assume r02- 0.56 A. Such magnitude of the radius is known from the quantum mechanics calculations [2]. According to this picture, 80-90 % of the crystal volume is occupied by the metal atom orbitals with radius (1.3-1.9) A, while the oxygen ions play a role of acceptors, which reduce occupancy of these orbitals ("indirect" dilution of the metal). A "direct" dilution of metals takes place in stoichiometric matrices. When r02- 0.56 A, channels with diameter 3.6 A present in the hexagonal matrix Ag3Pb2H2O6 directed along the "c" axis. The channels are filled by chains of the Ag2 molecules with atomic diameter of 2.6 A and the molecule concentration nB = 25.6 10²0 cm-3. The Bose-Einstein condensation (BEC) temperature TcB 400K is calculated for the electron effective mass value m*=7.5mₑ, where mₑ is the isolated electron mass. Three-dimensional networks of Na2 chains form in Na solutions in NH3 and WO3 as well (respectively, with nB=4.71 10²0 cm-3; Tc sim 180K; m*=5.0mₑ and nB=4.74 10²0 cm-3; Tc sim 91K; m*=10mₑ). Close magnitudes of the Ag2 and Na2 chains parameters respectively in NH3 and WO3 favors the opinion that all these structures have a composite structure and similar mechanisms of the high temperature superconductivity.