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An alternative way of linearizing the augmented-plane-wave method
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
2000 (English)In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 114, no 1, 15-20 p.Article in journal (Refereed) Published
Abstract [en]

A new basis set for a full potential treatment of crystal electronic structures is presented and compared to that of the well-known linearized augmented plane-wave (LAPW) method. The basis set consists of energy-independent augmented plane-wave functions combined with local orbitals. Each basis function is continuous over the whole unit cell but it may have a discontinuous slope at the muffin-tin boundaries, i.e. at the surfaces of atomic centered, non-overlapping spheres. This alternative way to linearize the augmented plane-wave method is shown to reproduce the accurate results of the LAPW method, but using a smaller basis set size. The reduction in number of basis functions is most significant for open structures.

Place, publisher, year, edition, pages
2000. Vol. 114, no 1, 15-20 p.
Keyword [en]
surfaces and interfaces, electronic band structure, molecules, core
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-89764DOI: 10.1016/S0038-1098(99)00577-3OAI: oai:DiVA.org:uu-89764DiVA: diva2:161500
Available from: 2002-04-05 Created: 2002-04-05 Last updated: 2013-05-30Bibliographically approved
In thesis
1. Augmented Planewaves, Developments and Applications to Magnetism
Open this publication in new window or tab >>Augmented Planewaves, Developments and Applications to Magnetism
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis concerns method development and applications in the field of first principles electronic structure calculations.

Augmented planewaves combine the simple planewaves with exact solutions of the Schrödinger equation for a spherical potential. This combination yields a very good set of basis functions for describing the electronic structure everywhere in a crystal potential. In the present work, developments of the original augmented planewave (APW) method are presented. It is shown that the exact APW eigenvalues can be found using information from the eigenvalues of the APW secular matrix. This provides a more efficient scheme to solve the APW eigenvalue problem, than the traditional evaluation of the secular determinant. Further, a new way of linearizing the APW method is presented and compared to the traditional linearized APW method (LAPW). Using a combination of the original APW basis functions and the so called local orbitals (lo), the APW+lo linearization is found to reproduce the results of the LAPW method, but already at a smaller basis set size. Another advantage of the new linearization is a faster convergence of forces, with respect to the basis set size, as compared to the LAPW method.

The applications include studies of the non-collinear magnetic configuration in the fcc-based high-temperature phase of iron, γ-Fe. The system is found to be extremely sensitive to volume changes, as well as to a tetragonal distortion of the cubic unit cell. A continuum of degenerate spin spiral configurations, including the global energy minimum, are found for the undistorted crystal. The in-plane anisotropy of the ideal interface between a ferromagnetic layer of bcc Fe and the semiconducting ZnSe crystal is also investigated. In contrast to the four-fold symmetric arrangement of the atoms at the interface, the in-plane magnetic anisotropy displays a large uniaxiality. The calculated easy axes are in agreement with experiments for both Se and Zn terminated interfaces. In addition, calculations of the hyperfine parameters were performed for Li intercalated battery materials.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. 67 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 701
Keyword
Physics, First principles electronic structure calculations, augmented planewaves, non-collinear magnetism, in-plane magnetic anisortopy, hyperfine parameters, Fysik
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-1928 (URN)91-554-5286-8 (ISBN)
Public defence
2002-04-26, Polhemssalen, Ångström laboratoriet, Uppsala, 10:15
Opponent
Available from: 2002-04-05 Created: 2002-04-05Bibliographically approved

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Nordström, Lars

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