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Efficient linearization of the augmented plane-wave method
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
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2001 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 64, no 19, 195134- p.Article in journal (Refereed) Published
Abstract [en]

We present a detailed analysis of the APW+lo basis set for band-structure calculations. This basis set consists of energy independent augmented plane-wave (APW) functions. The linearization is introduced through local orbitals evaluated at the same linearization energy as the APW functions. It is shown that results obtained with the APW+lo basis set converge much faster and often more systematically towards the final value. The APW+lo thereby allows accurate treatment of systems that were previously unaccessible to linearized APW. Furthermore, it is shown that APW+lo converges to the same total energy as LAPW provided the higher angular momenta l are linearized, either by adding extra local orbitals or treating them by LAPW. It is illustrated that the APW basis functions are much closer to the true form of the eigenfunctions than the LAPW basis functions. This is especially true for basis functions that have a strong energy dependence inside the sphere.

Place, publisher, year, edition, pages
2001. Vol. 64, no 19, 195134- p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-89765DOI: 10.1103/PhysRevB.64.195134OAI: oai:DiVA.org:uu-89765DiVA: diva2:161501
Available from: 2002-04-05 Created: 2002-04-05 Last updated: 2013-06-13Bibliographically 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.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 701
Physics, First principles electronic structure calculations, augmented planewaves, non-collinear magnetism, in-plane magnetic anisortopy, hyperfine parameters, Fysik
National Category
Physical Sciences
Research subject
urn:nbn:se:uu:diva-1928 (URN)91-554-5286-8 (ISBN)
Public defence
2002-04-26, Polhemssalen, Ångström laboratoriet, Uppsala, 10:15
Available from: 2002-04-05 Created: 2002-04-05Bibliographically approved

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