Predicting stable stoichiometries of compounds via evolutionary global space-group optimization

Giancarlo Trimarchi, Arthur J Freeman, Alex Zunger

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Whereas the Daltonian atom-to-atom ratios in ordinary molecules are well understood via the traditional theory of valence, the naturally occurring stoichiometries in intermetallic compounds Ap Bq, as revealed by phase-diagram compilations, are often surprising. Even equal-valence elements A and B give rise to unequal (p,q) stoichiometries, e.g., the 1:2, 2:1, and 3:1 ratios in Alp Scq. Moreover, sometimes different stoichiometries are associated with different lattice types and hence rather different physical properties. Here, we extend the fixed-composition global space-group optimization (GSGO) approach used to predict, via density-functional calculations, fixed-composition lattice types to identify simultaneously all the minimum-energy lattice types throughout the composition range. Starting from randomly selected lattice vectors, atomic positions and stoichiometries, we construct the T=0 "convex hull" of energy vs composition. Rather than repeat a set of GSGO searches over a fixed list of stoichiometries, we minimize the distance to the convex hull. This approach is far more efficient than the former one as a single evolutionary search sequence simultaneously identifies the lowest-energy structures at each composition and among these it selects those that are ground states. For Al-Sc we correctly identify the stable stoichiometries and relative structure types: AlSc2 -B 82, AlSc-B2, and Al2 Sc-C15 in the Nat =6 periodic cells, and Al2 Sc6 -D 019, AlSc-B2, and Al3 Sc-L 10 in the Nat =8 periodic cells. This extended evolutionary GSGO algorithm represents a step toward a fully ab initio materials synthesis, where compounds are predicted starting from sole knowledge of the chemical species of the constituents.

Original languageEnglish
Article number092101
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume80
Issue number9
DOIs
Publication statusPublished - Sep 3 2009

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Stoichiometry
stoichiometry
optimization
Chemical analysis
valence
Atoms
lattice energy
cells
lists
Ground state
Intermetallics
Phase diagrams
Density functional theory
intermetallics
atoms
Physical properties
physical properties
phase diagrams
Molecules
ground state

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Predicting stable stoichiometries of compounds via evolutionary global space-group optimization. / Trimarchi, Giancarlo; Freeman, Arthur J; Zunger, Alex.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 80, No. 9, 092101, 03.09.2009.

Research output: Contribution to journalArticle

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