Low-temperature structure of xi '-Al-Pd-Mn optimized by ab initio methods

Engel M, Frigan B, Santana A, Schopf D, Trebin HR, Mihalkovic M (2011)

Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2011

Journal

Physical Review B American Physical Society

Publisher: American Physical Society

Book Volume: 84

Journal Issue: 18

DOI: 10.1103/PhysRevB.84.184203

Abstract

We have studied and resolved occupancy correlations in the existing average structure model of the complex metallic alloy xi'-Al-Pd-Mn [Boudard et al., Philos. Mag. A 74, 939 (1996)], which has approximately 320 atoms in the unit cell and many fractionally occupied sites. Model variants were constructed systematically in a tiling-decoration approach and subjected to simulated annealing by use of both density functional theory and molecular dynamics with empirical potentials. To obtain a measure for thermodynamic stability, we reproduce the Al-Pd-Mn phase diagram at T = 0 K, and derive an enthalpy of formation for each structure. Our optimal structure resolves a cloud of fractionally occupied sites in pseudo-Mackay clusters. In particular, we demonstrate the presence of rotational degrees of freedom of an Al-9 inner shell, which is caged within two icosahedrally symmetric outer shells Al-30 and Pd-12. Outside these clusters, the chemical ordering on a chain of three nearby sites surprisingly breaks the inversion symmetry of the surrounding structure, and couples to an Al/vacancy site nearby. Our refined tiling-decoration model applies to any structure within the epsilon-phases family, including the metastable decagonal quasicrystalline phase.

Authors with CRIS profile

Michael Engel Lehrstuhl für Multiscale Simulation of Particulate Systems

Involved external institutions

Universität Stuttgart DE Germany (DE) Slovak Academy of Sciences (SAS) / Slovenská akadémia vied (SAV) SK Slovakia (SK)

How to cite

APA:

Engel, M., Frigan, B., Santana, A., Schopf, D., Trebin, H.-R., & Mihalkovic, M. (2011). Low-temperature structure of xi '-Al-Pd-Mn optimized by ab initio methods. Physical Review B, 84(18). https://doi.org/10.1103/PhysRevB.84.184203

MLA:

Engel, Michael, et al. "Low-temperature structure of xi '-Al-Pd-Mn optimized by ab initio methods." Physical Review B 84.18 (2011).

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