3 research outputs found
Ionocovalency and Applications 1. Ionocovalency Model and Orbital Hybrid Scales
Ionocovalency (IC), a quantitative dual nature of the atom, is defined and correlated with quantum-mechanical potential to describe quantitatively the dual properties of the bond. Orbiotal hybrid IC model scale, IC, and IC electronegativity scale, XIC, are proposed, wherein the ionicity and the covalent radius are determined by spectroscopy. Being composed of the ionic function I and the covalent function C, the model describes quantitatively the dual properties of bond strengths, charge density and ionic potential. Based on the atomic electron configuration and the various quantum-mechanical built-up dual parameters, the model formed a Dual Method of the multiple-functional prediction, which has much more versatile and exceptional applications than traditional electronegativity scales and molecular properties. Hydrogen has unconventional values of IC and XIC, lower than that of boron. The IC model can agree fairly well with the data of bond properties and satisfactorily explain chemical observations of elements throughout the Periodic Table
On the nature of antiferromagnetism in the CO_2 planes of oxide superconductors
Recent results on electrons and holes doped CuO 2 planes confirm the marked
covalency of CuO bonding, suggesting a band picture of long and short range
antiferromagnetism. The maxima of superconductive T c versus doping can be
related to the crossing by the Fermi level of the edges of the pseudogap due to
antiferromagnetic short range order (bonding edge for holes doping, antibonding
one for electrons doping). The symmetry of the superconductive gap can be
related to the Bragg scattering of electronic Bloch states near the edges of
the AF pseudogap. Assuming a standard phonon coupling, one then predicts for
commensurate AF a pure d symmetry of the superconductive gap for underdoped
samples and d symmetry plus an ip contribution increasing linearly with
overdoping. This seems in agreement with recent measurements of gap symmetry
for YBCO, but should be more fully tested, especially for electron doped
samples. The simple band approximation used here could no doubt be made more
realistic by a specific inclusion of electron correlations and by a better
description of AF short range order. Uncommensurate AF, as in LSCO, is not
considered here