WELCOME TO SJSU JV Acrivos et al., Physical Chemistry in the XX to XXI Centuries: Chemistry

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3*a = 1.155 nm


a a

Figures show SCF electron density contours, re>10-3/bohr3, TOTAL, HOMO, LUMO.

Many electron resonance interactions determine the bond distances in high temperature layer cuprate superconducting alloys, HTLSC: (Bi1.7Pb0.3Sr2Can-1CunO2n+4+δ)2,n<24, (2s:2:n-1:n). Indexed in ideal D174h symmetry, {an,bn,cn}={3.815Ǻ,a(1+ubn),2dP(n+3)(1+ucn)}u<1% the structure gives the experimental evidence that resonance reduces the Pauling ionic radii: 2(r(Cu+2)+r(O-2))= 4.2 > an > d(CuO)+2-3/2d(O3). Oxide melts form clusters of n-1 perovskite: [P][(CusO2)/_Ca/(CuO2)] stacks (at ideal AB stacking sites along the Cu4O4 square diagonal), and its center of symmetry inverted, [P*][(O2Cu)/Ca_/(O2Cu)]; dPd(CuO)+2-3/2d(O3) thick along the c-axis, that are intercalated in between high melting point, [S] [(CuO2)/OSr/BiO/OBi/SrO/(O2Cu)], hard stacks of layers, to obtain [P](n-1)[S][P*](n-1), cn/2 long chains of nm cross section, where the CuO2 exposed planes control the activity. An ideal D174h symmetry stoichiometric n-polymorph obtains by pairing of chains, according to the Gibbs free enthalpy of formation, DGn. But, the addition of perovskite stacks, by proximity reactions gives rise to mixed n'-polymorphs when cn'/2=Ncn, N=1,2,. or n'=Nn+3(N-1). A relation between the cluster size and the transition temperature to the superconducting state, Tc,n indicates that polarized free electron pairing, 2e-e2=, proposed to induce the phase transition, is favored in the intercalated perovskite stacks over the entire unit cell by: -DGn/kBTln((n+3)/(n-1)) 20meV/T-1.1 near Tc,n=2=87K, Tc,n=3=107K, to Tc,n'>7190K within the skin depth of the lower density n'-polymorphs, that float to the alloy surface on fast cooling and annealing at 848oC 5oC .