Work

A computational free energy reference for mechanically unstable phases

Year: 2025

Type: article

Abstract: The CALPHAD (CALculation of PHAse Diagram) framework relies heavily on the availability of a well-defined free energy for all possible phases, including metastable and even mechanically unstable phases. However, for phases that exhibit mechanical instability, the determination of the free energy represents a challenge, both experimentally and computationally. This situation hinders the seamless integration of experimental and ab initio thermodynamic data. A newly developed method, named “inflection-detection”, provides a practical computational solution to this problem with a sound theoretical basis. Extending upon existing energy calculations at absolute zero, we provide further evidence of this method’s effectiveness by computing the temperature-dependent free energy references for 22 elemental structures involving mechanically unstable phases and showing that they are reasonably consistent with the (often wide) range of values determined in earlier experimental assessments. This suggests the feasibility of a reliable computation-based reference free energy standard for mechanically unstable pure elements.

Source: Calphad

DOI: 10.1016/j.calphad.2025.102869

Authors: Hantong Chen, Qi-Jun Hong, Alexandra Navrotsky, Axel van de Walle

Institutions: Brown University, Arizona State University

Language: English

Topic: Thermodynamic and Structural Properties of Metals and Alloys

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,250

Funders: National Science Foundation, Brown University