skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Electronic Structure and Lattice Distortions in PbMg 1/3Nb 2/30 3 Studied with Dnsity Functional Theory Using the Linearized Augmented Plane-Wave Method


We investigated the local structural distortions of PMN

 [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 73; Journal Issue: 22
Country of Publication:
United States

Citation Formats

Suewattana, Malliga, and Singh, David J. Electronic Structure and Lattice Distortions in PbMg1/3Nb2/303 Studied with Dnsity Functional Theory Using the Linearized Augmented Plane-Wave Method. United States: N. p., 2006. Web. doi:10.1103/PhysRevB.73.224105.
Suewattana, Malliga, & Singh, David J. Electronic Structure and Lattice Distortions in PbMg1/3Nb2/303 Studied with Dnsity Functional Theory Using the Linearized Augmented Plane-Wave Method. United States. doi:10.1103/PhysRevB.73.224105.
Suewattana, Malliga, and Singh, David J. Sun . "Electronic Structure and Lattice Distortions in PbMg1/3Nb2/303 Studied with Dnsity Functional Theory Using the Linearized Augmented Plane-Wave Method". United States. doi:10.1103/PhysRevB.73.224105.
title = {Electronic Structure and Lattice Distortions in PbMg1/3Nb2/303 Studied with Dnsity Functional Theory Using the Linearized Augmented Plane-Wave Method},
author = {Suewattana, Malliga and Singh, David J},
abstractNote = {We investigated the local structural distortions of PMN},
doi = {10.1103/PhysRevB.73.224105},
journal = {Physical Review B},
number = 22,
volume = 73,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
  • The linearized-augmented-plane-wave (LAPW) method for thin films is generalized by removing the remaining shape approximation to the potential inside the atomic spheres. A new technique for solving Poisson's equation for a general charge density and potential is described and implemented in the film LAPW method. In the resulting full-potential LAPW method (FLAPW), all contributions to the potential are completely taken into account in the Hamiltonian matrix elements. The accuracy of the method: already well known for clean metal surfaces: is demonstrated for the case of a nearly free (noninteracting) O/sub 2/ molecule which is a severe test case of themore » method because of its large anisotropic charge distribution. Detailed comparisons show that the accuracy of the FLAPW results for O/sub 2/ exceeds that of existing state-of-the-art local-density linear-combination-of-atomic-orbitals (LCAO)-type calculations, and that taking the full potential LAPW results as a reference, the LCAO basis can be improved by adding off-site functions. Thus the full-potential LAPW is a unified method which is ideally suited to test not only molecular adsorption on surfaces, but also the components of the same system separately, i.e., the extreme limits of the molecule and the clean surface.« less
  • The electronic structure and properties of the cubic Laves phase (C15) compounds ZrZn/sub 2/ and ZrV/sub 2/ have been determined using our all-electron full-potential linearized-augmented-plane-wave (FLAPW) method for bulk solids. The computations were performed in two stages: (i) self-consistent warped muffin tin and (ii) self-consistent full potential. Spin-orbit coupling was included after either stage. The effects of the inclusion of the nonspherical terms inside the muffin tins on the eigenvalues is found to be small (of order 1 mRy). However, due to the fact that some of the bands near the Fermi level are flat, this effect leads to amore » much higher value of the density of states at E/sub F/ in ZnZr/sub 2/. The most important difference between the materials ZrZn/sub 2/ and ZrV/sub 2/ is the position of the d bands derived from the Zr and V atoms. Consequently, these materials have completely different Fermi surfaces. We have investigated the magnetic properties of these compounds by evaluating their generalized Stoner factors and found agreement with experiment. Our results for the superconducting transition temperature for these materials is found to be strongly dependent on the spin fluctuation parameter sp/. Of course, because of the magnetic transition, superconductivity cannot be observed in ZnZr/sub 2/.« less
  • The structural parameters of various Haegg phases (H or M{sub n+1}AX{sub n} phases) are studied experimentally by x-ray and electron spectroscopies, x-ray diffraction, and ab initio full potential as well as full mutiple scattering theoretical calculations. Experimentally it was found that the structure of all ternary compounds analyzed herein are relaxed. The values of the lattice parameters and relaxations obtained from ab initio calculations are in excellent agreement with those deduced from the analysis of the experimental data. The bonding scheme has been analyzed and the charge transfer between constituting atoms determined. It is demonstrated that the strength and electricalmore » transport properties in these materials are principally governed by the metallic planes. For the solid solution (Ti{sub 0.5}Nb{sub 0.5}){sub 2}AlC, the most salient result is that the basal planes are corrugated, which could explain the solid solution scattering observed in this H phase.« less
  • We have performed self-consistent (SC) band structure calculations for the A15 compounds V/sub 3/X and Nb/sub 3/X, X = Al, Ga, Si, Ge, and Sn, using the augmented-plane-wave (APW) method. Relativistic effects (except the spin-orbit interaction) have been included in each SC cycle, along with corrections to the usual muffin-tin approximation. The latter apply the APW wave functions outside of the muffin-tin spheres to compute the interstitial charge densities and potentials. The resulting interstitial potential has full cubic symmetry (no spherical averaging). The final SC potentials were used to generate energies and wave functions on a cubic mesh of 35more » k points in 1/48th of the Brillouin zone. These results were interpolated onto a finer mesh of 969 k points using a symmetrized Fourier method; the densities of states (DOS), N (E), were determined using tetrahedral integration. These accurate interpolation methods allow us to determine the DOS on a fine energy scale ( +- 3 mRy) around the Fermi level E/sub F/, where we find large variations for the compounds V/sub 3/Ga, V/sub 3/Si, and Nb/sub 3/Sn. This correlates well with the fact that these compounds have high superconducting transition temperatures (T/sub c/) and anomalous electronically derived properties. The energy bands of the A15 materials exhibit significant variations even amongst the isoelectronic compounds. All compounds possess very flat bands that evolve from the GAMMA/sub 12/ state near E/sub F/ and give rise to the sharp peaks in N (E). For V/sub 3/Ga, V/sub 3/Si, and Nb/sub 3/Sn, E/sub F/ falls within several mRy of GAMMA/sub 12/ so that these flat bands are responsible for the sharp structure in N (E) at E/sub F/. We find that Nb/sub 3/Ge and Nb/sub 3/Si have relatively low values of N (E/sub F/), which suggests that the high T/sub c/'s observed in films of the former and predicted for the latter are due to unusual mechanisms.« less
  • The isostructural ..gamma..-..cap alpha.. phase transition of Ce which occurs at 8 kbar has been studied by means of fully self-consistent (non-muffin-tin potential) linearized-augmented-plane-wave energy band calculations carried out for five different values of the lattice constant. In contradiction to the 4f electron promotional model of the transition, the results yield essentially one 4f electron to be occupied in each phase but with the 4f wave function somewhat less localized, and therefore more bandlike, in the ''collapsed'' ..cap alpha.. phase. A singly occupied 4f state is shown to be consistent with the available experimental data. These results strongly support themore » picture of a 4f localized bold-arrow-left-right itinerant transition at the ..gamma..-..cap alpha.. transition and conflict with the promotional model in which some fraction of 4f electrons are transferred to the sd conduction bands. The weaker bonding of the 4f electrons, compared to that of the 6s-5d valence electrons, accounts for ..cap alpha..-Ce appearing to have 3.5--3.7 bonding electrons in some respects. Calculation of the superconducting transition temperature T/sub c/ suggests that a small spin-fluctuation contribution detrimental to superconductivity is necessary to account for the very low value of T/sub c/ in ..cap alpha..-Ce. Comparison with specific-heat data also suggests a spin-fluctuation contribution to the effective mass; susceptibility data point to a moderate exchange enhancement in ..cap alpha..-Ce. We calculate a spin-susceptibility (Stoner) enhancement that increases with temperature, in agreement with experiment up to 150 K, and which tends to diverge at higher temperatures. Certain experiments are suggested which could help greatly in understanding further some important characteristics of the ..cap alpha.. phase.« less