Search results for "Valence electron"
showing 10 items of 56 documents
Full Configuration-Interaction Study on the Tetrahedral Li4 Cluster
2008
International audience; The Li4 cluster low lying electronic states were studied. In particular we investigated the tetrahedral geometry at full CI and coupled cluster level, with basis sets of increasing quality. The 5A2 electronic state, characterized by having all the valence electrons unpaired, forming a quite stable no-pair bonding state, was studied in greater detail. In order to compare the energies we also studied the Li4 rhombus singlet ground state. The ability of coupled cluster with perturbative triples to correctly reproduce energy levels in a quasi-degenerate system was validated with respect to the full CI.
Sodium atoms and clusters on graphite by density functional theory
2004
Sodium atoms and clusters $(Nl~5)$ on graphite (0001) are studied using density functional theory, pseudopotentials and periodic boundary conditions. A single Na atom is observed to bind at a hollow site 2.45 \AA{} above the surface with an adsorption energy of 0.51 eV. The small diffusion barrier of 0.06 eV indicates a flat potential energy surface. Increased Na coverage results in a weak adsorbate-substrate interaction, which is evident in the larger separation from the surface in the cases of ${\mathrm{Na}}_{3},$ ${\mathrm{Na}}_{4},$ ${\mathrm{Na}}_{5},$ and the $(2\ifmmode\times\else\texttimes\fi{}2)$ Na overlayer. The binding is weak for ${\mathrm{Na}}_{2},$ which has a full valence el…
Band structure tuning of Heusler compounds: Spin- and momentum-resolved electronic structure analysis of compounds with different band filling
2019
Physical review / B 103(5), 054407 (2021). doi:10.1103/PhysRevB.103.054407
Tailoring the electronic structure of half-metallic Heusler alloys
2009
We investigated element-specific magnetic moments and the spin-resolved unoccupied density of states (DOS) of polycrystalline ${\text{Co}}_{2}\text{Ti}Z$ $(Z=\text{Si},\text{ }\text{Ge},\text{ }\text{Sn},\text{ }\text{Sb})$, ${\text{Co}}_{2}{\text{Mn}}_{x}{\text{Ti}}_{1\ensuremath{-}x}\text{Si}$ and ${\text{Co}}_{2}{\text{MnGa}}_{1\ensuremath{-}x}{\text{Ge}}_{x}$ Heusler alloys using circular dichroism in x-ray absorption spectroscopy (XMCD). We find a small $(l0.03{\ensuremath{\mu}}_{B})$ Ti moment oriented antiparallel and a large $(g3{\ensuremath{\mu}}_{B})$ Mn moment oriented parallel to the Co moment of approximately $1{\ensuremath{\mu}}_{B}$ per atom in the investigated compounds. Orb…
Monte-Carlo calculations of keV electron and positron slowing down in solids
1983
A Monte-Carlo simulation technique based on the screened Rutherford differential cross section for the elastic scattering and Gryzinski's semiempirical expression for the inelastic core and valence electron excitation is used to describe electrons and positrons slowing down in solids. The theoretical results are compared with the experimental backscattering, absorption and transmission results for aluminum, silicon, copper, and gold thin film and semi-infinite targets and good agreement is observed. The simulated stopping profiles are fitted with a simple analytic expression. The profiles are Laplace-transformed to give a useful data base for analyzing phenomena associated with slow positro…
Configuration-interaction calculations of jellium clusters by the nuclear shell model
1994
Configuration-interaction (CI) calculations are performed on Na clusters of up to 20 atoms within the spherical jellium model, with particular attention paid to the magic clusters with N=2, 8, and 20. The interacting valence electrons are assumed to move in the Coulomb field of the jellium core. The numerical work is carried out by the nuclear-structure code oxbash modified to handle LS coupling. The many-particle bases are constructed of harmonic-oscillator single-particle states extending over 11 major shells and, alternatively, of single-particle states generated by the local-spin-density approximation (LSDA). The calculated quantities include ground- and excited state energies, ionizati…
Many-body origin of the plasmon resonance in small metal clusters
1994
The origin of the plasmon excitation in small metal clusters is studied within the jellium model through ab initio electronic-structure calculations based on the nuclear shell model. In the limit of infinite size, the plasmon classically represents pure harmonic motion of the center of mass of the valence electrons. It is shown that this limit is already well approximated by clusters of only eight electrons.
Hard X-ray resonant electronic spectroscopy in transition metal oxides
2005
K-edge X-ray absorption and 2p-XPS spectra of 3d-element oxides present spectral features which cannot be explained within a simple one-electron model. These features reveal the fine electronic structure of transition metal (TM) oxides valence states resulting from hybridized TM-3d and O-2p states, and the correlations between these valence electrons. In this paper, we show how resonant electronic spectroscopy (resonant Auger or resonant photoelectron spectroscopy) around the TM K-edge can be used to interpret the structures of the threshold and, with the help of theoretical calculation, to determine the electronic configuration of the excited ion. Quadrupolar transitions towards localized …
Unrestricted shapes of light nuclei in the local-density approximation: Comparison with jellium clusters
1995
Abstract The shapes of light nuclei are studied within density-functional theory. The Kohn-Sham method and the local-density approximation are used. No symmetry restrictions are imposed. A parallel study is made of monovalent atomic clusters described on the jellium model. The shapes obtained for nuclei with Z = N = 2–22 show a striking similarity to those of atomic clusters of an equal number of valence electrons. Moments of inertia, when suitably normalized, are virtually identical. The calculated nuclear quadrupole moments are found insensitive to the effective interaction and in good agreement with experiment. Similar shape coexistence is established in both systems.
Restoring the valence-shell stabilization in Nd 140
2020
A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain E2 and M1 transition matrix elements of Nd-140 using the multistep Coulomb-excitation code GOSIA. The absolute M1 strengths, B(M1; 2(2)(-) -> 2(1)(+)) = 0.033(8)mu(2)(N), B(M1 ; 2(3)(+) -> 2(1)(+)) = 0.26(-0.10)(+0.11)mu(2)(N), and B(M1; 2(4)+ -> 2(1)(+)) <0.04 mu(2)(N) identify the 2(3)(+) state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of Nd-140. The degree of F-spin mixing in Nd-140 was quantified with the determination of the mixing matrix element VF-mix <7(-7)(-13) keV. Peer reviewed