First principles investigation of phase stability in the B-Pt alloy system

TL;DR

This study uses first-principles calculations to analyze phase stability in the B-Pt alloy system, clarifying phase identities, correcting database inconsistencies, and explaining the eutectic's depth through thermodynamic insights.

Contribution

It provides a detailed ab-initio investigation of B-Pt phases, identifying discrepancies in existing databases and linking thermodynamic properties to eutectic behavior.

Findings

Identified inconsistencies in crystallographic databases.

Matched experimental phases with specific structures.

Explained eutectic depth via low energy and high entropy of the liquid.

Abstract

The B-Pt alloy system contains several Pt-rich phases exhibiting complex structures, many with partial site occupation. It also exhibits a deep (nearly 1000 degrees C) eutectic. We evaluate the ab-initio total energies of the crystalline solids to clarify the identity and character of the phases. Our work identifies inconsistencies in materials databases such as the Inorganic Crystallographic Structure Database and the ASM Phase Diagram Database, but our total energy calculations allow us to match up experimentally reported stable phases with specific structures. High temperature Gibbs free energy calculations in the liquid and solid states at the composition Pt$_2$B reveal that the depth of the eutectic arises from the low energy and high entropy of the liquid state.