Frederick E. Wang

Some crystal chemical aspects of A3B(β-W) type compounds

Abstract All the known A3B compounds with the A15(β-W) type structure have been compiled. The compilation shows that the formation of the A3B compounds to be strongly dependent on atomic orbitals of both the A and B elements. Specifically A elements come exclusively from the transition atoms of 4-A 5-A and 6-A groups, whereas B elements come exclusively from 8-A, 9-A, 10-A groups of transition atoms as well as from 1-B, 2-B, 3-B, 4-B and 5-B groups of nontransition atoms. Roughly, there is a one-to-one correspondence between the population (therefore the stability) of the A3B compounds and their superconducting critical temperature; the more stable is the compound, the higher is the critical temperature.

Multiple metal-metal bonding and A-chain integrity in superconducting A3B (β-tungsten) alloy☆

Abstract Charge overlap and molecular orbital energies for the -(M2)- linear chain unit are computed for selected transition metals. For valid comparison, uniform parameters are used starting with the type of dnsp excited configuration of the atoms that is favorable to linear digonal hybrid bonding. Stabilities of the chains are then compared. Bond order and bond energies of σ, π, and δ bonds for the d molecular orbitals are deduced. Results support the existence of linear chains of group V or group VI atoms as the A atoms in superconducting A3B alloys. Conjugated resonance structures are drawn for all multiple bonds in the chains. A possible relationship between chain integrity (and conjugation) and conductivity in such alloys is suggested.

Special singlet and triplet geminal correlations for modeling fullerenes and superconductive cuprates

Abstract Two-electron-bonding geminals ΨΛ(x1,x2), in cupric of superconductivity as well as in carbons of fullerenes out of four electrons ΨΛ(x1,x2,x3,x4), have been explained. In superconductivity cases, La8Sr8Cu8O28 and La12Sr4Cu8O30 with free 4 Cu in D4h have been considered. Fullerenes C40 (Td) and C48 (Oh) with free π radicals of 4 carbons in D4h have also been considered. Singlet and triplet geminals, 1,3 Ψ Λ (x 1 ,x 2 ), are in terms of 1,3 φ n,n+1 (x 1 ,x 2 )= 1 2 [φ n (x 1 )φ n+1 (x 2 )±φ n (x 2 )φ n+1 (x 1 )], in 4 Cu and 4 carbons of a2μ, egxz, egyz and b1μ or b2μ.