New Pseudo-Phase Structure for $\alpha$-Pu

TL;DR

This paper introduces a new pseudo-phase crystal structure for alpha-plutonium, based on an orthorhombic distortion, which links the alpha and gamma phases and aids in understanding plutonium's complex phase diagram.

Contribution

The authors propose a novel pseudo-phase structure for alpha-plutonium derived from a distorted gamma-phase structure, providing a new perspective on plutonium's phase relationships.

Findings

Total energy similar to existing structures in calculations

Pseudo-phase structure closely related to gamma-phase with different ratios

Potential to explore Pu phase diagram through this new structure

Abstract

In this paper we propose a new pseudo-phase crystal structure, based on an orthorhombic distortion of the diamond structure, for the ground-state $\alpha$-phase of plutonium. Electronic-structure calculations in the generalized-gradient approximation give approximately the same total energy for the two structures. Interestingly, our new pseudo-phase structure is the same as the Pu $\gamma$-phase structure except with very different b/a and c/a ratios. We show how the contraction relative to the $\gamma$ phase, principally in the $z$ direction, leads to an $\alpha$-like structure in the [0,1,1] plane. This is an important link between two complex structures of plutonium and opens new possibilities for exploring the very rich phase diagram of Pu through theoretical calculations.