Polymorphism of Iron. Part 2. Paradoxes of Metallic Bonding Models

Abstract

This study considers the main stages of the evolution of ideas about the kind of bonding in metals. The paradigm of chemical bonding in metals is based on the metallic bonding model known as the rigid atomic ion frame immersed in electron gas of free electrons or the electron gas model (P. Drude, H.A. Lorentz, Ch. Kittel, W. Hume-Rothery, and others). As an alternative to the official Drude–Lorentz electron gas theory, V.K. Grigorovich has proposed a modernized model and the metallic bonding theory based on the concept of the “multiple overlapping of outer valence orbitals”. V.Yu. Gankin has recently proposed a revolutionary metallic bonding model on electrostatic principles of “electron nuclear isomerization and electrostatic dynamic resonant interaction of valence electrons” or the atom-ion model. The models developed by Grigorovich and Gankin have largely evolved and deepened the idea about the kind of particle interaction among structural components of crystal metal lattice but have not gone beyond the basic limitations of the Drude–Lorentz model in terms of the antiphysical notion of electron gas of free electrons. None of the considered metallic bonding models explains the ionization degree of metal atoms, formation and effect of metallic bonds, and generation of threshold shear stresses in the crystal lattice of iron which are responsible for diffusionless transformation at polymorphous transformation temperature. Similarly, the theory of rigid ion frame immersed in electron gas fails to explain the phenomenon of mercury properties.