From Entropy to Compression: Competing Thermodynamic Drivers of Structural Transitions in Transition Metals

Abstract

Solid-solid phase transitions in metals are traditionally driven by changes in density or external pressure. Here we show that, under strong electronic excitation, structural stability is governed by the interplay between electronic effects and compression. Using finite-temperature density functional theory, we construct pressure-temperature phase diagrams for 15 metals spanning hcp-, fcc-, and bcc-ground-state structures. The results reveal a systematic reduction of structural diversity with increasing electronic temperature, with stability increasingly dominated by the fcc structure, while hcp remains a persistent secondary phase and bcc stability is progressively suppressed. At elevated temperatures, fcc is broadly favored, whereas bcc is stabilized primarily by compression, leading to a material-dependent competition across the periodic table. These findings provide a unified framework for understanding structural transformations in electronically excited metals and highlight the importance of considering both electronic excitation and pressure in describing phase stability far from equilibrium.