First Principles Phase Diagram Calculations for the Octahedral-Interstitial System ZrO_X, 0 ≤ X ≤ 1/2

Abstract

First principles based phase diagram calculations were performed for the octahedral-interstitial solid solution system αZrO_X (αZr[ ]_(1-X)O_X; [ ] = vacancy; 0 ≤X ≤1/2). The cluster expansion method was used for ground state analysis, and to calculate the phase diagram. The predicted diagram has four ordered ground-states in the range 0 ≤X ≤1/2, but one of these, at X=5/12, is predicted to disproportionate at T≈20 K, well below the experimentally investigated range T ≈420 K. Thus, at T≳420 K, the first-principles based calculation predicts three ordered phases rather than the four that have been reported by experimentalists.

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