Universal phase transitions of B1 structured stoichiometric transition-metal carbides

TL;DR

This study systematically investigates high-pressure phase transitions in B1-structured transition-metal carbides using ab initio calculations, revealing universal transition routes and stable new phases that can be recovered after pressure release.

Contribution

It uncovers universal phase transition pathways and predicts stable new phases in B1-structured TMCs under high pressure, expanding understanding of their structural behavior.

Findings

Identified two universal phase transition routes in TMCs under pressure.

Discovered four new phases resulting from atomic slips.

Only the TlI'-type phase remains stable after pressure release.

Abstract

The high-pressure phase transitions of B1-structured stoichiometric transition metal carbides (TMCs, TM=Ti, Zr, Hf, V, Nb, and Ta) were systematically investigated using ab initio calculations. These carbides underwent universal phase transitions along two novel phase-transition routes, namely, B1\rightarrowdistorted TlI (TlI')\rightarrowTlI and/or B1\rightarrowdistorted TiB (TiB')\rightarrowTiB, when subjected to pressures. The two routes can coexist possibly because of the tiny enthalpy differences between the new phases under corresponding pressures. Four new phases result from atomic slips of the B1-structured parent phases under pressure. After completely releasing the pressure, taking TiC as a representative of TMCs, only its new TlI'-type phase is mechanically and dynamically stable, and may be recovered.