Wannier-function approach to spin excitations in solids Şaşıoğlu, Ersoy Schindlmayr, Arno Friedrich, Christoph Freimuth, Frank Blügel, Stefan ddc:530 We present a computational scheme to study spin excitations in magnetic materials from first principles. The central quantity is the transverse spin susceptibility, from which the complete excitation spectrum, including single-particle spin-flip Stoner excitations and collective spin-wave modes, can be obtained. The susceptibility is derived from many-body perturbation theory and includes dynamic correlation through a summation over ladder diagrams that describe the coupling of electrons and holes with opposite spins. In contrast to earlier studies, we do not use a model potential with adjustable parameters for the electron-hole interaction but employ the random-phase approximation. To reduce the numerical cost for the calculation of the four-point scattering matrix we perform a projection onto maximally localized Wannier functions, which allows us to truncate the matrix efficiently by exploiting the short spatial range of electronic correlation in the partially filled d or f orbitals. Our implementation is based on the full-potential linearized augmented-plane-wave method. Starting from a ground-state calculation within the local-spin-density approximation (LSDA), we first analyze the matrix elements of the screened Coulomb potential in the Wannier basis for the 3d transition-metal series. In particular, we discuss the differences between a constrained nonmagnetic and a proper spin-polarized treatment for the ferromagnets Fe, Co, and Ni. The spectrum of single-particle and collective spin excitations in fcc Ni is then studied in detail. The calculated spin-wave dispersion is in good overall agreement with experimental data and contains both an acoustic and an optical branch for intermediate wave vectors along the [100] direction. In addition, we find evidence for a similar double-peak structure in the spectral function along the [111] direction. To investigate the influence of static correlation we finally consider LSDA+U as an alternative starting point and show that, together with an improved description of the Fermi surface, it yields a more accurate quantitative value for the spin-wave stiffness constant, which is overestimated in the LSDA. American Physical Society 2010 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_6501 https://ris.uni-paderborn.de/record/18560 https://ris.uni-paderborn.de/download/18560/18561 Şaşıoğlu E, Schindlmayr A, Friedrich C, Freimuth F, Blügel S. Wannier-function approach to spin excitations in solids. <i>Physical Review B</i>. 2010;81(5). doi:<a href="https://doi.org/10.1103/PhysRevB.81.054434">10.1103/PhysRevB.81.054434</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.81.054434 info:eu-repo/semantics/altIdentifier/issn/1098-0121 info:eu-repo/semantics/altIdentifier/issn/1550-235X info:eu-repo/semantics/altIdentifier/wos/000274998000084 info:eu-repo/semantics/altIdentifier/arxiv/1002.4897 info:eu-repo/semantics/openAccess