CRYSTAL CHEMICAL DESIGN OF HIGH-T_c SUPERCONDUCTORS ON THE GROUND OF OXIDE AND INTERMETAL LAYERS. L. M. Volkova, S. A. Polyshchuk, Institute of Chemistry, Far Eastern Branch of Russian Academy of Science, Vladivostok 690022, Russia, S. A. Magarill, Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Science, Novosibirsk 630090, Russia

The design of new compounds (B₂C₂)(MO₂) and A₂(B₂C₂)(MO₂) - candidates in superconductors of Nd₂CuO₄ and Sr₂Mn₃As₂O₂ structure types, which consist of alternating oxide planes of CuO₂-type and intermetal layers such as in compounds of the ThCr₂Si₂ or CaBe₂Ge₂ structure types will be presented. The paper will discuss the possibility of these systems formation on the ground of B and M = Cu, Mo, Nb, Ta, Re, W, Ru or Ti and C = Si, Ge, P, As, Bi or Te. The double role of B₂C₂-layer will be shown. It combines the functions of CuO₂-layers and interstitial layers (CuO, TlO, Bi₂O₂ and so on) in high-T_c cuprates.

This design was carried out on the base of our own crystal chemical concept of appearing "conductance coupled oscillating displacements of atoms" by transition in superconducting state. On the ground of the crystal chemical investigations of the high-T_c superconductors we proposed that the appearance of high-T_c superconductivity near the Mott metal-insulator phase boundary is associated with transition of system in dynamic state with coupled oscillating atom displacements. The correlation between the coupled oscillating displacements of atoms, changes of magnetic properties and transfer of charge carriers determines the transition of materials in superconducting state. 2D-systems with mutual controllability of layers by the presence of atoms at critical near-neighbor distances are favorable to appearance the dynamic state. The mixed valent compounds of the transition metals with low energy of intervalent transfer, where one of the states has a magnetic moment, my be a basis for these systems.