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Full-Text Articles in Engineering Physics
Reliable First-Principles Alloy Thermodynamics Via Truncated Cluster Expansions, Nikolai A. Zarkevich, Duane D. Johnson
Reliable First-Principles Alloy Thermodynamics Via Truncated Cluster Expansions, Nikolai A. Zarkevich, Duane D. Johnson
Nikolai A. Zarkevich
In alloys cluster expansions (CE) are increasingly used to combine first-principles electronicstructure calculations and Monte Carlo methods to predict thermodynamic properties. As a basis-set expansion in terms of lattice geometrical clusters and effective cluster interactions, the CE is exact if infinite, but is tractable only if truncated. Yet until now a truncation procedure was not well defined and did not guarantee a reliable truncated CE. We present an optimal truncation procedure for CE basis sets that provides reliable thermodynamics. We then exemplify its importance in Ni3V, where the CE has failed unpredictably, and now show agreement to a range of …
Anisotropy Of Exchange Stiffness And Its Effect On The Properties Of Magnets, K. D. Belashchenko
Anisotropy Of Exchange Stiffness And Its Effect On The Properties Of Magnets, K. D. Belashchenko
Kirill Belashchenko Publications
Using the spin-spiral formulation of the tight-binding linear muffin-tin orbital method, the principal components of the exchange stiffness tensor are calculated for typical hard magnets including tetragonal CoPt-type and hexagonal YCo5 alloys. The exchange stiffness is strongly anisotropic in all studied alloys. This anisotropy makes the domain wall surface tension anisotropic. Competition between this anisotropic surface tension and magnetostatic energy controls the formation and dynamics of nanoscale domain structures in hard magnets. Anisotropic domain wall bending is described in detail from the general point of view and with application to cellular Sm–Co magnets. It is shown that the repulsive …