期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：10
DOI：10.1073/pnas.2117416119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Over the years, many unusual chemical phenomena have been discovered at high pressures, yet our understanding of them is still very fragmentary. Our paper addresses this from the fundamental level by exploring the key chemical properties of atoms—electronegativity and chemical hardness—as a function of pressure. We have made an appropriate modification to the definition of Mulliken electronegativity to extend its applicability to high pressures. The change in atomic properties, which we observe, allows us to provide a unified framework explaining (and predicting) many chemical phenomena and the altered behavior of many elements under pressure.
Abundant evidence has shown the emergence of exotic chemical phenomena under pressure, including the formation of unexpected compounds and strange crystal structures. In many cases, there is no convincing explanation for these phenomena, and there are virtually no chemical rules or models capable of predicting or even rationalizing these phenomena. Here, we calculate, as a function of pressure, two central chemical properties of atoms, electronegativity and chemical hardness, which can be seen as the first- and second-order chemical potentials. Mulliken electronegativity, which is the negative of the chemical potential of the electron in a given atom relative to the vacuum, is appropriately modified; instead of taking the vacuum (impossible under high pressure), we take the homogeneous electron gas as reference. We find that for most elements, chemical hardness and electronegativity decrease with pressure, consistent with pressure-induced metallization. Furthermore, we discover that pressure-induced
s-
d orbital transfer makes Ni, Pd, and Pt “pseudo–noble-gas” atoms with a closed d-shell configuration, and the elements preceding them (Fe and, especially, Co, Rh, and Ir) electron acceptors, while the elements right after them (Cu, Ag, Zn, and Cd) become highly electropositive. We show the explicative and predictive power of our electronegativity and chemical hardness scales.
