3 research outputs found
Phonons from Density-Functional Perturbation Theory using the All-Electron Full-Potential Linearized Augmented Plane-Wave Method FLEUR
Phonons are quantized vibrations of a crystal lattice that play a crucial
role in understanding many properties of solids. Density functional theory
(DFT) provides a state-of-the-art computational approach to lattice vibrations
from first-principles. We present a successful software implementation for
calculating phonons in the harmonic approximation, employing density-functional
perturbation theory (DFPT) within the framework of the full-potential
linearized augmented plane-wave (FLAPW) method as implemented in the electronic
structure package FLEUR. The implementation, which involves the Sternheimer
equation for the linear response of the wave function, charge density, and
potential with respect to infinitesimal atomic displacements, as well as the
setup of the dynamical matrix, is presented and the specifics due to the
muffin-tin sphere centered LAPW basis-set and the all-electron nature are
discussed. As a test, we calculate the phonon dispersion of several solids
including an insulator, a semiconductor as well as several metals. The latter
are comprised of magnetic, simple, and transition metals. The results are
validated on the basis of phonon dispersions calculated using the finite
displacement approach in conjunction with the FLEUR code and the phonopy
package, as well as by some experimental results. An excellent agreement is
obtained.Comment: 44 pages, 6 figure
Atomic force calculations within the all-electron FLAPW method: Treatment of core states and discontinuities at the muffin-tin sphere boundary
We analyze the accuracy of the atomic force within the all-electron full-potential linearized augmented plane-wave (FLAPW) method using the force formalism of Yu et al. [Phys. Rev. B 43, 6411 (1991)]. A refinement of this formalism is presented that explicitly takes into account the tail of high-lying core states leaking out of the muffin-tin sphere and considers the small discontinuities of LAPW wave function, density, and potential at the muffin-tin sphere boundaries. For MgO and EuTiO3 it is demonstrated that these amendments substantially improve the acoustic sum rule and the symmetry of the force constant matrix. Sum rule and symmetry are realized with an accuracy of μHtr/aB
Phonons from density-functional perturbation theory using the all-electron full-potential linearized augmented plane-wave method FLEUR *
Phonons are quantized vibrations of a crystal lattice that play a crucial role in understanding many properties of solids. Density functional theory provides a state-of-the-art computational approach to lattice vibrations from first-principles. We present a successful software implementation for calculating phonons in the harmonic approximation, employing density-functional perturbation theory within the framework of the full-potential linearized augmented plane-wave method as implemented in the electronic structure package FLEUR. The implementation, which involves the Sternheimer equation for the linear response of the wave function, charge density, and potential with respect to infinitesimal atomic displacements, as well as the setup of the dynamical matrix, is presented and the specifics due to the muffin-tin sphere centered linearized augmented plane-wavebasis-set and the all-electron nature are discussed. As a test, we calculate the phonon dispersion of several solids including an insulator, a semiconductor as well as several metals. The latter arecomprised of magnetic, simple, and transition metals. The results are validated on the basis of phonon dispersions calculated using the finite displacement approach in conjunction with theFLEUR code and the phonopy package, as well as by some experimental results. An excellent agreement is obtained