Search results for "Quantum"

Ab initio calculations of the atomic and electronic structure of BaZrO3 (111) surfaces

2013

Abstract The paper presents and discusses the results of calculations of surface relaxations and energetics for the polar (111) surface of BaZrO 3 using a hybrid B3LYP description of exchange and correlation. On the (111) surface, both Zr- and BaO 3 -terminations were analyzed. For both Zr and BaO 3 -terminated BaZrO 3 (111) surface upper layer atoms, with the sole exception of BaO 3 -terminated surface Ba atoms, relax inwards. The Zr-terminated BaZrO 3 (111) surface second layer Ba atoms exhibit the strongest relaxation between all Zr and BaO 3 -terminated BaZrO 3 (111) surface atoms. The calculated surface relaxation energy for Zr-terminated BaZrO 3 (111) surface is almost fifteen times l…

On-surface Synthesis of a Chiral Graphene Nanoribbon with Mixed Edge Structure.

2020

Abstract Chiral graphene nanoribbons represent an important class of graphene nanomaterials with varying combinations of armchair and zigzag edges conferring them unique structure‐dependent electronic properties. Here, we describe the on‐surface synthesis of an unprecedented cove‐edge chiral GNR with a benzo‐fused backbone on a Au(111) surface using 2,6‐dibromo‐1,5‐diphenylnaphthalene as precursor. The initial precursor self‐assembly and the formation of the chiral GNRs upon annealing are revealed, along with a relatively small electronic bandgap of approximately 1.6 eV, by scanning tunnelling microscopy and spectroscopy.

First principles calculations of SrZrO3 bulk and ZrO2-terminated (001) surface F centers

2016

Abstract Using a supercell model and B3PW hybrid exchange-correlation functional in the framework of the density functional theory (DFT), as it is implemented in the CRYSTAL computer code, we performed ab initio calculations for the F -center located in the SrZrO 3 bulk and on the ZrO 2 -terminated (001) surface. According to the results of performed relaxation of atoms around the defect, two nearest Zr and four Sr atoms are repulsed, but all oxygen atoms are attracted towards both, the bulk and (001) surface F -center. The displacement magnitudes of atoms surrounding the bulk F -center are smaller than around the (001) surface F -center. The B3PW calculated SrZrO 3 bulk optical band gap (5…

Influence of the filling factor on the spectral properties of plasmonic crystals

2006

Plasmonics crystals (PCs) comprised of finite-size triangular lattices of gold bumps deposited on a gold thin film are studied by means of a near-field optical microscope. The plasmonic crystals fabricated by electron-beam lithography are illuminated by an incident surface plasmon polariton excited in the Kretschmann-Raether configuration at the gold/air thin-film interface for incident free-space wavelengths in the range $740--820\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. Based on the measurement of the surface plasmon polariton (SPP) damping distance in the crystals, the existence of a band gap for an incident SPP traveling along the two symmetry axes $\ensuremath{\Gamma}M$ and $\ensuremath…

A large-energy-gap oxide topological insulator based on the superconductor BaBiO3

2013

Mixed-valent perovskite oxides based on BaBiO3 (BBO) are, like cuperates, well-known high-Tc superconductors. Recent ab inito calculations have assigned the high-Tc superconductivity to a correlation-enhanced electron--phonon coupling mechanism, stimulating the prediction and synthesis of new superconductor candidates among mixed-valent thallium perovskites. Existing superconductivity has meant that research has mainly focused on hole-doped compounds, leaving electron-doped compounds relatively unexplored. Here we demonstrate through ab inito calculations that BBO emerges as a topological insulator (TI) in the electron-doped region, where the spin-orbit coupling (SOC) effect is significant.…

Electron delocalization in mixed-valence Keggin polyoxometalates. Ab initio calculation of the local effective transfer integrals and its consequence…

2002

We present a quantitative evaluation of the influence of the electron transfer on the magnetic properties of mixed-valence polyoxometalates reduced by two electrons. For that purpose, we extract from valence-spectroscopy ab initio calculations on embedded fragments the value of the transfer integrals between W nearest-neighbor atoms in a mixed-valence alphaPW(12)O(40) polyoxowolframate Keggin anion. In contradiction with what is usually assumed, we show that the electron transfer between edge-sharing and corner-sharing WO(6) octahedra have very close values. Considering fragments of various ranges, we analyze the accuracy of calculations on fragments based on only two WO(5) pyramids which s…

Charm production in the CERN hyperon beam

1994

First results on charm production by the Σ- hyperon beam experiment WA89 at CERN are presented. Estimates are given for thexF and nuclearA dependence of the inclusive cross-section of D-mesons. Preliminary results on charm baryon production are shown.

Erratum to: “Low lying S=−1 excited baryons and chiral symmetry”

2002

Limits to the fixed center approximation to Faddeev equations: The case of theϕ(2170)

2011

The fixed center approximation to the Faddeev equations has been used lately with success in the study of bound systems of three hadrons. It is also important to set the limits of the approach in those problems to prevent proliferation of inaccurate predictions. In this paper, we study the case of the $\ensuremath{\phi}(2170)$, which has been described by means of Faddeev equations as a resonant state of $\ensuremath{\phi}$ and $K\overline{K}$, and show the problems derived from the use of the fixed center approximation in its study. At the same time, we also expose the limitations of an alternative approach recently proposed.

Infinite momentum frame calculation of semileptonic heavyΛb→Λctransitions including HQET improvements

1997

We calculate the transition form factors that occur in heavy {Lambda}-type baryon semileptonic decays such as, e.g., in {Lambda}{sub b}{r_arrow}{Lambda}{sub c}{sup +}+l{sup {minus}}+{bar {nu}}{sub l}. We use Bauer-Stech-Wirbel-type infinite momentum frame wave functions for the heavy {Lambda}-type baryons which we assume to consist of a heavy quark and a light spin-isospin zero diquark system. The form factors at q{sup 2}=0 are calculated from the overlap integrals of the initial and final {Lambda}-type baryon states. To leading order in the heavy mass scale the structure of the form factors agrees with the HQET predictions including the normalization at zero recoil. The leading order {omeg…