A1 Refereed original research article in a scientific journal
Elastic anomalies and long/short-range ordering effects: A first-principles investigation of the AgcPd1-c solid solution
Authors: Hoffmann M, Marmodoro A, Nurmi E, Kokko K, Vitos L, Ernst A, Hergert W
Publisher: AMER PHYSICAL SOC
Publication year: 2012
Journal: Physical Review B
Journal name in source: PHYSICAL REVIEW B
Journal acronym: PHYS REV B
Article number: ARTN 094106
Number in series: 9
Volume: 86
Issue: 9
Number of pages: 10
ISSN: 1098-0121
DOI: https://doi.org/10.1103/PhysRevB.86.094106
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/3227564
We investigate the elastic properties of the binary alloy Ag-Pd. The lattice constant of this system shows significant deviations from the linear behavior anticipated by the semi-empirical Vegard's rule. This effect was formerly studied by assuming total substitutional disorder, and described by the coherent potential approximation (CPA). Theoretical phase diagram investigations have however suggested three ordered phases at low temperatures, and we extend our first-principles investigation to include such scenarios through the adoption of an extended unit cell representation and a recently developed multisublattice generalization of the original CPA. This allows us to explore equilibrium lattice constant and bulk modulus within a unified approach even in the presence of partial long-range order. We obtain significant variations of the bulk modulus in comparison to the totally disordered picture, and again very rich deviations from more intuitive predictions of a simple linear behavior. We follow former suggestions to analyze the different regimes in connection with topological transitions of the Fermi surface, examined through Bloch spectral function calculations.
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