7 research outputs found
Calculation of electronic properties of amorphous alloys
We describe the application of the
locally-self-consistent-multiple-scattering (LSMS)[1] method to amorphous
alloys. The LSMS algorithm is optimized for the Intel XP/S-150, a
multiple-instruction-multiple-data parallel computer with 1024 nodes and 2
compute processors per node. The electron density at each site is determined by
solving the multiple scattering equation for atoms within a specified distance
of the atom under consideration. Because this method is carried out in real
space it is ideal for treating amorphous alloys. We have adapted the code to
the calculation of the electronic properties of amorphous alloys. In these
calculations we determine the potentials in the atomic sphere approximation
self consistently at each site, unlike previous calculations[2] where we
determined the potentials self consistently at an average site. With these
self-consistent potentials, we then calculate electronic properties of various
amorphous alloy systems. We present calculated total electronic densities of
states for amorphous NiP and NiPdP with 300
atoms in a supercell.Comment: 10 pages, plain tex, 2 figures. Paper accepted for publication in
Proceedings of LAM-9 and Journal of non-Crystalline Solids. Please request
preprints from J.C. Swihart ([email protected]
Ab-initio calculation of Kerr spectra for semi-infinite systems including multiple reflections and optical interferences
Based on Luttinger's formulation the complex optical conductivity tensor is
calculated within the framework of the spin-polarized relativistic screened
Korringa-Kohn-Rostoker method for layered systems by means of a contour
integration technique. For polar geometry and normal incidence ab-initio Kerr
spectra of multilayer systems are then obtained by including via a 2x2 matrix
technique all multiple reflections between layers and optical interferences in
the layers. Applications to Co|Pt5 and Pt3|Co|Pt5 on the top of a semi-infinite
fcc-Pt(111) bulk substrate show good qualitative agreement with the
experimental spectra, but differ from those obtained by applying the commonly
used two-media approach.Comment: 32 pages (LaTeX), 5 figures (Encapsulated PostScript), submitted to
Phys. Rev.
Block bond-order potential as a convergent moments-based method
The theory of a novel bond-order potential, which is based on the block
Lanczos algorithm, is presented within an orthogonal tight-binding
representation. The block scheme handles automatically the very different
character of sigma and pi bonds by introducing block elements, which produces
rapid convergence of the energies and forces within insulators, semiconductors,
metals, and molecules. The method gives the first convergent results for
vacancies in semiconductors using a moments-based method with a low number of
moments. Our use of the Lanczos basis simplifies the calculations of the band
energy and forces, which allows the application of the method to the molecular
dynamics simulations of large systems. As an illustration of this convergent
O(N) method we apply the block bond-order potential to the large scale
simulation of the deformation of a carbon nanotube.Comment: revtex, 43 pages, 11 figures, submitted to Phys. Rev.
Recommended from our members
Multi-teraflops spin dynamics studies of the magnetic structure of FeMn/Co interfaces
The authors have used the power of massively parallel computers to perform first principles spin dynamics (SD) simulations of the magnetic structure of Iron-Manganese/Cobalt (FeMn/Co) interfaces. These large scale quantum mechanical simulations, involving 2016-atom super-cell models, reveal details of the orientational configuration of the magnetic moments at the interface that are unobtainable by any other means. Exchange bias, which involves the use of an antiferromagnetic (AFM) layer such as FeMn to pin the orientation of the magnetic moment of a proximate ferromagnetic (FM) layer such as Co, is of fundamental importance in magnetic multilayer storage and read head devices. Here the equation of motion of first principles SD is used to perform relaxations of model magnetic structures to the true ground (equilibrium) state. Our code is intrinsically parallel and has achieved a maximum execution rate of 2.46 Teraflops on the IBM SP at the National Energy Research Scientific Computing Center (NERSC)