Chemical Bonding and Thermodynamics in Superconductivity and Superfluidity

Abstract

Superconductivity and superfluidity are physical states that occur in a variety of chemical and physical systems. These physical states share a common type of real, or virtual, chemical bonding. Each of the systems discussed herein contain at least one real, or effective, coordinate covalent bond. This is formed from an electron pair donor species and an electron pair acceptor species. When the electronegativity difference between the electron pair donor and acceptor species is sufficiently small, the resultant coordinate covalent bond density can be substantial. If delocalized, this bond density can result in a significant increase in the electron pair orbital volume relative to that of the parent species, and an increase in the valence shell orbital entropy. In terms of the normalized Gibbs-Helmholtz equation, this results in a concomitant decrease in free energy of the delocalized electronic system. A decrease in free energy to negative values can support a boson state, and superconductivity. A clear example of these principles is the occurrence of superconductivity in the ceramic material, MgB 2 . These generalizations apply to superconducting elements, high temperature superconductors, superconducting alloys, and equivalently to superfluid 4 He.

Orbital Approach to High Temperature Superconductivity

“…It has been proposed that a classical coordinate covalent bond, CCB, is the basic bonding responsible for superconductivity [3]. A CCB contains 2 paired electron spins (a Lewis pair) supported by an electron pair donor (EPD) species, and an electron pair acceptor (EPA) species.…”

“…Since elemental Cu has only one electron in the valence shell it cannot support superconductivity [3].…”