Search results for " clusters"

showing 10 items of 1091 documents

Nonlocal properties of dynamical three-body Casimir-Polder forces

2005

We consider the three-body Casimir-Polder interaction between three atoms during their dynamical self-dressing. We show that the time-dependent three-body Casimir-Polder interaction energy displays nonlocal features related to quantum properties of the electromagnetic field and to the nonlocality of spatial field correlations. We discuss the measurability of this intriguing phenomenon and its relation with the usual concept of stationary three-body forces.

Electromagnetic fieldPhysicsQuantum PhysicsGeneral Physics and AstronomyFOS: Physical sciencesSpatial field correlationsRelativistic quantum mechanicsCasimir effectQuantization (physics)Open quantum systemQuantum nonlocalityClassical mechanicsQuantum mechanicsNonlocalityThree-body forcePhysics::Atomic and Molecular ClustersPhysics::Atomic PhysicsQuantum dissipationQuantum Physics (quant-ph)Introduction to quantum mechanics
researchProduct

Van der Waals Interactions in a Magneto-Dielectric Medium

2007

The van der Waals interaction between two ground-state atoms is calculated for two electrically or magnetically polarizable particles embedded in a dispersive magneto-dielectric medium. Unlike previous calculations which infer the atom-atom interaction from the dilute-medium limit of the macroscopic, many-body van der Waals interaction, the interaction is calculated directly for the system of two atoms in a magneto-dielectric medium. Two approaches are presented, the first based on the quantized electromagnetic field in a dispersive medium without absorption and the second on Green functions that allow for absorption. We show that the correct van der Waals interactions are obtained regardle…

Electromagnetic fieldPhysicsQuantum PhysicsVan der Waals surfaceVan der Waals strainFOS: Physical sciencesMolecular physicsAtomic and Molecular Physics and OpticsMany-body problemsymbols.namesakePolarizabilitysymbolsPhysics::Atomic and Molecular ClustersVan der Waals radiusPhysics::Atomic PhysicsAtomic physicsvan der Waals forceQuantum Physics (quant-ph)Absorption (electromagnetic radiation)
researchProduct

Time-dependent Maxwell field operators and field energy density for an atom near a conducting wall

2009

We consider the time evolution of the electric and magnetic field operators for a two-level atom, interacting with the electromagnetic field, placed near an infinite perfectly conducting wall. We solve iteratively the Heisenberg equations for the field operators and obtain the electric and magnetic energy density operators around the atom (valid for any initial state). Then we explicitly evaluate them for an initial state with the atom in its bare ground state and the field in the vacuum state. We show that the results can be physically interpreted as the superposition of the fields propagating directly from the atom and the fields reflected on the wall. Relativistic causality in the field …

Electromagnetic fieldPhysicsvacuum fluctuationQuantum PhysicsMagnetic energyField (physics)Vacuum stateFOS: Physical sciencesOptical fieldAtomic and Molecular Physics and OpticsMagnetic fieldQuantum electrodynamicQuantum mechanicsQuantum electrodynamicsPhysics::Atomic and Molecular ClustersBoundary value problemCasimir-Polder forcesGround stateQuantum Physics (quant-ph)
researchProduct

The adhesion nature of the Ag/MgO(100) interface: an ab initio study

1998

The atomic and electronic structure of the Ag/MgO(100) interface are calculated by means of the ab initio Hartree-Fock approach combined with a supercell model. The electronic density distribution and the interface binding energy/distance are analyzed for different Ag adsorption positions, slabs of different thicknesses and varying Ag surface coverage. It is demonstrated that the adhesion energy arises mainly due to the electrostatic interaction of substrate atoms with a complicated charge redistribution in the metal layer(s), characterized by large quadrupole moments as well as electron density redistribution towards bridge and hollow positions between the nearest and next-nearest Ag atoms…

Electron densityChemistryNuclear TheoryBinding energyAb initioGeneral Physics and AstronomyElectronic structureMolecular physicsCondensed Matter::Materials ScienceAdsorptionQuadrupolePhysics::Atomic and Molecular ClustersRedistribution (chemistry)Physics::Atomic PhysicsPhysical and Theoretical ChemistryAtomic physicsNuclear ExperimentElectronic density
researchProduct

Theoretical study of the molecular structure and the stability of neutral and reduced tetracyanoethylene

2003

Abstract The molecular structure and the stability of neutral, anionic, and dianionic tetracyanoethylene (TCNE) have been studied with MP2, coupled-cluster (CC), and density functional theory (DFT) procedures. The optimized geometries are in agreement with the available experimental data, although significant deviations for the CN bond distance have been obtained at the MP2 level. The adiabatic electron affinity of TCNE calculated with the B3LYP method is overestimated by 0.32 eV. In the light of the CC results, the source of such an overestimation is suggested to lie on the theoretical approach, rather than on a too low experimental value.

Electron densityGeneral Physics and AstronomyTetracyanoethyleneMolecular physicsBond lengthchemistry.chemical_compoundMolecular geometrychemistryComputational chemistryAb initio quantum chemistry methodsElectron affinityPhysics::Atomic and Molecular ClustersMoleculeDensity functional theoryPhysics::Chemical PhysicsPhysical and Theoretical ChemistryChemical Physics Letters
researchProduct

Effect of Vacancies on Positron Annihilation and Hyperfine Interactions in Fe-Al Alloys - <i>Ab Initio</i> Study

2012

Vacancies occupying different sub-lattices of D03 structure of Fe3Al alloy were investigated by the full potential linearized augmented plane wave method. The calculations basing on the super-cell approach have been performed for the vacancy concentrations of 1.6 and 3 at.%. For both concentrations the sub-lattice preference for vacancy location was determined. The dependence of vacancy formation energy on magnetic state of structure has been found. The positron lifetimes for the annihilation in the bulk (Fe3Al) and in vacancies have been investigated basing on the ab initio results for the electron density. The effect of vacancies on spin magnetic moment and hy-perfine parameters of Fe ato…

Electron densityMaterials scienceAnnihilationCondensed matter physicsAlloyAb initioengineering.materialCondensed Matter PhysicsAtomic and Molecular Physics and OpticsSpin magnetic momentCondensed Matter::Materials SciencePositronVacancy defectPhysics::Atomic and Molecular ClustersengineeringGeneral Materials ScienceHyperfine structureSolid State Phenomena
researchProduct

Increased conductivity of a hole transport layer due to oxidation by a molecular nanomagnet

2008

Thin film transistors based on polyarylamine poly?N,N?-diphenyl-N,N ?bis?4-hexylphenyl?- ?1,1?biphenyl?-4,4?-diamine ?pTPD? were fabricated using spin coating in order to measure the mobility of pTPD upon oxidation. Partially oxidized pTPD with a molecular magnetic cluster showed an increase in mobility of over two orders of magnitude. A transition in the mobility of pTPD upon doping could also be observed by the presence of a maximum obtained for a given oxidant ratio and subsequent decrease for a higher ratio. Such result agrees well with a previously reported model based on the combined effect of dipolar broadening of the density of states and transport manifold filling. Peer Reviewed

Electron mobilityMaterials scienceOrganic compounds.Analytical chemistryDipolar broadeningGeneral Physics and AstronomySpin coatingHole mobilityElectronic density of statesConductivityOxidacióCompostos orgànicsElectrical resistivity and conductivity:FÍSICA [UNESCO]Molecular clustersOrganic compoundsOxidationDopingElectrical conductivityOxidation.Molecular nanomagnetMolecular magnetic clusterMolecular magnetism Nanostructured materialsSpin coatingDopingUNESCO::FÍSICAElectric conductivity.Thin film transistorsNanostructured materialsConductivitat elèctricaNanomagnet:Enginyeria electrònica::Microelectrònica [Àrees temàtiques de la UPC]Doping ; Electrical conductivity ; Electronic density of states ; Hole mobility ; Molecular clusters ; Molecular magnetism Nanostructured materials ; Organic compounds ; Oxidation ; Spin coating ; Thin film transistorsDensity of statesNanostructured materials.Hole transport layerMaterials nanoestructuratsOrder of magnitude
researchProduct

"Table 17" of "Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in sqrt{s} = 7 TeV pp collisio…

2016

Number of b-tagged jets in the combined electron plus three jets W+jets and top control region.

Electron productionAstrophysics::High Energy Astrophysical PhenomenaSUSY7000.0Jet ProductionP P --> E- .GE.3JET MM XNP P --> E+ .GE.3JET MM XInclusiveNonlinear Sciences::Exactly Solvable and Integrable SystemsProton-Proton ScatteringPhysics::Atomic and Molecular ClustersHigh Energy Physics::ExperimentSupersymmetry
researchProduct

"Table 3" of "Search for lepton flavour violation in the emu continuum with the ATLAS detector in sqrt(s) = 7 TeV pp collisions at the LHC"

2012

The ratios of the observed and expected upper cross section limits to the theoretical cross sections as a function of the scalar top mass.

Electron productionIntegrated Cross Section7000.0NCross SectionP P --> E+ MU- XSIGbehavioral disciplines and activitiesMuon productionInclusiveNonlinear Sciences::Exactly Solvable and Integrable SystemsProton-Proton ScatteringPhysics::Atomic and Molecular ClustersP P --> E- MU+ Xpsychological phenomena and processes
researchProduct

Ab initio molecular orbital study of SenS4−nN4 (n = 0−4)

1995

Abstract We report an ab initio study of Se n S 4− n N 4 ( n = 0−4). The full geometry optimization for each molecule was performed at the Hartree-Fock level of theory involving the MIDI-4 ∗ basis sets for atomic orbitals. The correction for electron correlation was carried out for optimized geometries by utilizing the second-order Moller-Plesset (MP2) perturbation theory. The fundamental vibrations calculated for all molecular species verified that all molecules lie at the local minima. All molecules showed cage structures similar to those observed experimentally for S 4 N 4 and Se 4 N 4 . The calculated bond parameters of S 4 N 4 and Se 4 N 4 were in good agreement with the experimental v…

Electronic correlationChemistryBinding energyAb initioCondensed Matter PhysicsBiochemistryBond lengthCrystallographysymbols.namesakePhysics::Atomic and Molecular ClusterssymbolsSingle bondMolecular orbitalPhysics::Chemical PhysicsPhysical and Theoretical Chemistryvan der Waals forceAtomic physicsBasis setJournal of Molecular Structure: THEOCHEM
researchProduct