In a groundbreaking study that challenges long-standing paradigms in chemistry, researchers at the University at Buffalo have revealed that the role of core electrons—once believed to be chemically inert—may be far more dynamic and influential, even under ordinary conditions here on Earth’s surface. Traditional teachings have held that core electrons reside too close to the atomic nucleus to partake in bonding interactions, leaving only the valence electrons to govern the chemical behavior of elements. However, this new research invites a reexamination of such assumptions, particularly in alkali metals where core electrons, specifically semicore electrons, demonstrate surprising activity when subjected to surprisingly modest pressures.
The focus of this investigation was the semicore electrons in alkali metals, a group renowned for their exceptional reactivity and position in the first column of the periodic table. Using sophisticated quantum chemical simulations powered by high-performance computational facilities, the team explored how these electrons influence phase transitions in compounds formed between alkali metals and fluorine. Their work was motivated by the notorious B1-B2 structural phase transition, a pressure-induced rearrangement of atomic crystals from an octahedral to a cubic lattice structure, familiar from the classical sodium chloride to cesium chloride conversion.
Quantum chemical calculations harnessed to unravel this complexity rely on approximations designed to make the famously intractable Schrödinger equation solvable for systems involving many interacting electrons. Historically, conventional wisdom attributed the need for immense pressures—on the order of hundreds of gigapascals—to activate core electron bond participation. This study defies that notion by demonstrating electron bonding activation at pressure levels far less severe, within the range of a few gigapascals, a regime found not only deep within Earth’s crust but intriguingly close to everyday atmospheric pressures.
In a stunning discovery, the researchers uncovered that cesium, among the heaviest alkali metals, exhibits semicore electron bonding even under ambient conditions. This defies previous theories that core electron involvement was exclusive to extreme planetary interiors. By analyzing cesium chloride’s crystal structure, the team deduced that the B2 phase—characterized by a cubic lattice stabilized by semicore electron activity—exists naturally without the necessity of high-pressure environments.
The implications of such a finding extend beyond academic curiosity. If semicore electrons contribute to bonding under conditions previously considered benign, this necessitates a reappraisal of theoretical models that predict elemental behavior in the Earth’s mantle and cores of terrestrial planets. The participation of these electrons could fundamentally influence key geophysical phenomena such as a planet’s density profile, tectonic dynamics, and magnetic field generation.
The team, led by SUNY Distinguished Professor Eva Zurek and co-researcher Stefano Racioppi, utilized state-of-the-art computational models facilitated by the University at Buffalo’s Center for Computational Research. Their modeling offers a high-resolution window into electron density distributions and bonding interactions that had eluded experimental characterization thus far. This theoretical advance outlines a paradigm shift in the understanding of chemical elements under pressure, with semicore electrons playing an indispensable role previously underestimated or overlooked in chemical physics.
Even more compelling is how the study’s insights could ripple into planetary science. If electrons alter their bonding behavior as a function of pressure in ways that differ from established expectations, current models of planetary formation and evolution could be incomplete or inaccurate. For example, shifts in bonding states at lower pressures could impact material properties that control mantle convection and core dynamics right down to magnetic field intensity and stability, both crucial for planetary habitability.
While these revelations stem primarily from computational simulation, the authors are cautious yet hopeful that experimental verification is within reach. They propose targeted experiments involving X-ray diffraction under controlled pressures to validate the role of semicore electrons in the bonding transformation and the B1-B2 phase transition. Such efforts could cement the theoretical predictions, potentially reshaping textbooks and inspiring new directions in materials chemistry and geophysics.
This investigation into semicore electron activation stands as a powerful reminder of how even well-established scientific doctrines remain open to challenge with the emergence of novel technology and rigorous inquiry. By pushing the boundaries of quantum chemical modeling, the researchers at Buffalo have not only illuminated the nuanced behavior of electrons deeply embedded in atomic structures but also opened pathways to understanding the underlying chemistry that defines planetary compositions and transformations.
With the support of the U.S. National Science Foundation’s Center for Matter at Atomic Pressure, this fusion of quantum computational chemistry and geophysical relevance represents the vanguard of interdisciplinary research. It underscores how foundational electron interactions—at scales far smaller than conventional chemical bonds—can dictate macroscopic properties that influence entire planetary bodies and conditions for life.
Ultimately, this study propels a revisitation of fundamental chemical bonding theories. It compels scientists to consider that electrons formerly deemed inert within atoms may emerge as active agents under a spectrum of hitherto unexpected pressures. This evolution in understanding expands the horizon for material science, planetary geology, and the quest to decode the complexities of matter both on Earth and across the cosmos.
Subject of Research:
Quantum chemical behavior of semicore electrons in alkali metals under pressure
Article Title:
Activation of Semicore Electrons in Alkali Metals and Their Role in the B1–B2 Phase Transition under Pressure
News Publication Date:
25-Aug-2025
Web References:
https://pubs.acs.org/doi/10.1021/jacs.5c08582
Image Credits:
Eva Zurek/University at Buffalo
Keywords:
Chemical elements, Chemical structure, Covalent bonds, Molecular chemistry, Materials, Heavy metals, Geophysics, Quantum mechanics
