Pressure-induced new chemistry*

Abstract

It has long been recognized that the valence electrons of an atom dominate the chemical properties, while the inner-shell electrons or outer empty orbital do not participate in chemical reactions. Pressure, as a fundamental thermodynamic variable, plays an important role in the preparation of new materials. More recently, pressure stabilized a series of unconventional stoichiometric compounds with new oxidation states, in which the inner-shell electrons or outer empty orbital become chemically active. Here, we mainly focus on the recent advances in high-pressure new chemistry including novel chemical bonding and new oxidation state, identified by first-principles swarm intelligence structural search calculations. The aim of this review is to provide an up-to-date research progress on the chemical bonding with inner-shell electrons or outer empty orbital, abnormal interatomic charge transfer, hypervalent compounds, and chemical reactivity of noble gases. Personal outlook on the challenge and opportunity in this field are proposed in the conclusion.

Conceptual density functional theory under pressure: Part I. XP-PCM method applied to atoms

“…[20][21][22] Generally, bonds strengthen and coordination numbers rise as the pressure increases and each electronic energy level is inuenced to a different extent, possibly resulting in a redistribution of electrons over the shell structure. [18][19][20]23 Finally, at the highest currently achievable pressures in a laboratory experiment, metallization is expected to occur for all compounds due to the forced overlap of orbitals (e.g. at approximately 450 GPa for hydrogen) and even the spherical symmetry of atoms can be broken to obtain a more efficient stacking.…”

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

“…Fricke and Waber (Fricke and Waber, 1971 ; Fricke, 1975 ) had already speculated about raised valences of elements 119 Uue and 120 Ubn. In more recent years, computations and experiments up to the megabar range have established the stability of alkali and alkaline-earth polyhalides under high pressure met inside the planets (Dong et al, 2015 , 2017 ; Zhu et al, 2015 ; Goesten et al, 2017 ; Miao et al, 2017 ; Luo et al, 2018 ; Lin et al, 2019 ; Rahm et al, 2019 ). Under standard conditions polyfluorides CsF n and BaF n are at most metastable, with a decay barrier that may render their temporary stability possible under standard pressure only at exotically low temperatures (see e.g., Rogachev et al, 2015 ; Vent-Schmidt et al, 2015 ).…”

Superconducting ternary hydrides under high pressure

“…The application of pressure provides a route to access unusual chemistry, 52,53 and disclose new materials with intriguing properties. 16,36,51,54 High-pressure experiment requires strict equipment, and the process of exploring proper conditions needs high cost and even delays the discovery of new materials.…”