Search results for "ELECTRONIC STRUCTURE"

Electronic Properties, Band Structure, and Fermi Surface Instabilities ofNi1+/Ni2+NickelateLa3Ni2O6, Isoelectronic with Superconducting Cuprates

2009

Electronic structure calculations were performed for the mixed-valent Ni(1+)/Ni(2+) nickelate La3Ni2O6, which exhibits electronic instabilities of the Fermi surface similar to that of the isostructural superconducting La2CaCu2O6 cuprate. La3Ni2O6 shows activated hopping, which fits to Mott's variable-range-hopping model with localized states near the Fermi level. However, a simple local spin density approximation calculation leads to a metallic ground state. The calculations including local density approximation+Hubbard U and hybrid functionals indicate a multiply degenerate magnetic ground state. For electron-doped La2ZrNi2O6, which is isoelectronic with La2CaCu2O6, an antiferromagnetic in…

Superconductivity in palladium-based Heusler compounds

2009

This work reports on four more Heusler superconductors: ${\text{Pd}}_{2}\text{ZrAl}$, ${\text{Pd}}_{2}\text{HfAl}$, ${\text{Pd}}_{2}\text{ZrIn}$, and ${\text{Pd}}_{2}\text{HfIn}$. These compounds exhibit superconducting transition temperatures ranging from 2.4--3.8 K as determined by resistivity measurements. According to their behavior in an external magnetic field, all compounds are type II bulk superconductors. The occurrence of superconductivity was predicted for these compounds using electronic structure calculations. The electronic structures exhibit van Hove singularities (saddle points) at the $L$ point. These lead to a maximum in the corresponding density of states and superconduct…

Effect of zero-point motion on the superconducting transition temperature of PdH(D)

1984

Using self-consistent density functional formalism we show that the electronic structure of PdH(D) is influenced by the zero-point vibration of hydrogen and deuterium. This quantum effect makes a small but significant contribution to the superconducting transition temperature ${T}_{c}$ of PdH(D). The reverse isotope effect on ${T}_{c}$ is found to be dominated by the changes in the force constants between PdH and PdD.

Electronic and structural properties of palladium-based Heusler superconductors

2008

Abstract This work reports on superconductivity in the Heusler compounds Pd2ZrAl and Pd2HfAl. Magnetisation and resistance measurements were carried out to verify their superconducting states. The compounds exhibit transition temperatures of 3.2 K (Zr) and 3.4 K (Hf). From their behaviour in external magnetic fields, it was determined that both compounds are type II superconductors. Similar to the half-metallic ferromagnets, the superconducting Heusler compounds follow an electron counting scheme based on theoretical considerations. As found from ab initio calculations, the superconductivity can be explained by a valence instability at the L -point, that has been used as design criterion.

Investigation of Many‐Body Effects in the Quasi‐Two‐Dimensional Electronic System of Organic Charge‐Transfer Salts

2019

Morphology and electronic structure of bcc Co(110) and fcc/hcp Co(111) on Fe(110) investigated by STM and STS

2009

Abstract We report on the growth of ultrathin epitaxial Co films on Fe(1 1 0) examined by scanning tunneling microscopy and spectroscopy (STM and STS). At room temperature Co forms pseudomorphic, ideally ordered body-centered cubic (bcc) layers for the first two monolayers as confirmed by atomically resolved STM images. This is in contrast to the related case of Co/Cr(1 1 0) where a superstructure occurs in the second layer. The third monolayer forms a close-packed structure and causes a transformation of the buried second monolayer into a close-packed structure. The Fe(1 1 0) substrate strongly influences the electronic structure of the first Co monolayer as concluded from the dI / dU spec…

On the use of reduced active space in CASSCF calculations

2014

Abstract The complete active space self-consistent field (CASSCF) method is one of the most used approaches to explore theoretically non-adiabatic photochemical processes in medium-size molecular systems. It is also frequently utilized in direct dynamics studies because this method offers a reliable description of the electronic state mixing in the regions of surface crossings (conical intersections). In this context, however, the large computational demand required to perform such on-the-fly molecular dynamics simulations using CASSCF as the electronic structure method means that only relatively small active space can be handled (typically not more than 10 electrons distributed in 10 orbit…

Determination of surface and interface magnetic properties for the multiferroic heterostructure Co/BaTiO3using spleed and arpes

2016

Co/BaTiO$_3$(001) is one of the most interesting multiferroic heterostructures as it combines different ferroic phases, setting this way the fundamentals for innovative technical applications. Various theoretical approaches have been applied to investigate the electronic and magnetic properties of Co/BaTiO$_3$(001). Here we determine the magnetic properties of 3 ML Co/BaTiO$_3$ by calculating spin-polarized electron diffraction as well as angle-resolved photoemission spectra, with both methods being well established as surface sensitive techniques. Furthermore, we discuss the impact of altering the BaTiO$_3$ polarization on the spectra and ascribe the observed changes to characteristic deta…

Ab InitioCalculations of the Atomic and Electronic Structure of SrZrO3(111) Surfaces

2012

The paper presents and discusses the results of calculations of surface relaxations and energetics for the polar (111) surface of SrZrO3 using a hybrid B3LYP description of exchange and correlation. On the (111) surface, I consider both Zr- and SrO3-terminations. For both Zr and SrO3-terminated SrZrO3 (111) surfaces upper layer atoms relax inwards. The second layer atoms, with the sole exception of Zr-terminated SrZrO3 (111) surface Sr atom, relax outwards. The calculated surface relaxation energy for Zr-terminated SrZrO3 (111) surface is almost sixteen times larger, than the surface relaxation energy for SrO3-terminated SrZrO3 (111) surface. The surface energy for Zr-terminated SrZrO3 (111…

Enhanced CDW Transitions in Nb3X4(X = S, Se, Te): Intercalation and Surface Effects

2004

A x Nb 3 X 4 (A = In, Tl, ZnHg; X = S, Se, Te) compounds show CDW instabilities dependent on the type and concentration of intercalate. Tl or In intercalation flattens the Fermi surfaces and supports CDW formation. In the corresponding DOS spectrum the Fermi level is shifted towards coincidence with a small peak, derived mainly from the Nb dz 2 orbital. Localized modulated regions observed in STM images of Nb 3 X 4 at room temperature represent precursor effects to full CDW formation.