Search results for "HF Calculations"

showing 3 items of 3 documents

A computational study of some electric and magnetic properties of gaseous BF3 and BCl3

2005

We present the results of an extended computational study of the electric and magnetic properties connected to Cotton-Mouton birefringences, on the trifluoro- and trichloroborides in the gas phase. The electric dipole polarizabilities, magnetizabilities, quadrupole moments, and higher-order hypersusceptibilities—expressed as quadratic and cubic frequency-dependent response functions—are computed within Hartree-Fock, density-functional, and coupled-cluster response theories employing singly and doubly augmented correlation-consistent basis sets and London orbitals in the magnetic property calculations. The results, which illustrate the capability of time-dependent density-functional theory f…

BirefringenceBirefringenceCondensed matter physicsChemistryElectron correlationsGeneral Physics and AstronomyMagnetic susceptibilityBoron compounds; Polarisability Quadrupole moments ; HF calculations ; Density functional theory ; Coupled cluster calculations ; Electron correlations ; Magnetic anisotropy ; Magnetic susceptibility ; BirefringenceUNESCO::FÍSICA::Química físicaMagnetic susceptibilityMagnetic anisotropyDipoleAtomic orbitalBoron compoundsCoupled cluster calculationsQuadrupolePolarisability Quadrupole momentsDensity functional theoryDensity functional theoryPhysical and Theoretical ChemistryAtomic physicsAnisotropy:FÍSICA::Química física [UNESCO]HF calculationsMagnetic anisotropy
researchProduct

Fast noniterative orbital localization for large molecules

2006

We use Cholesky decomposition of the density matrix in atomic orbital basis to define a new set of occupied molecular orbital coefficients. Analysis of the resulting orbitals ("Cholesky molecular orbitals") demonstrates their localized character inherited from the sparsity of the density matrix. Comparison with the results of traditional iterative localization schemes shows minor differences with respect to a number of suitable measures of locality, particularly the scaling with system size of orbital pair domains used in local correlation methods. The Cholesky procedure for generating orthonormal localized orbitals is noniterative and may be made linear scaling. Although our present implem…

Density matrixPhysicsBasis (linear algebra)Minor (linear algebra)General Physics and AstronomySTO-nG basis setsOrbital calculationsUNESCO::FÍSICA::Química físicaHF calculations ; Orbital calculationsPhysics and Astronomy (all)Atomic orbitalComputational chemistryMolecular orbitalOrthonormal basisStatistical physicsPhysical and Theoretical Chemistry:FÍSICA::Química física [UNESCO]HF calculationsCholesky decompositionThe Journal of Chemical Physics
researchProduct

Current density maps, magnetizability, and nuclear magnetic shielding tensors of bis-heteropentalenes. II. Furo-furan Isomers

2004

Magnetic susceptibility and nuclear magnetic shielding at the nuclei of bis-heteropentalenes formed by two furan units ([2,3-b], [3,2-b], [3,4-b], and [3,4-c] isomers) have been computed by several approximated techniques and a large Gaussian basis set to achieve near Hartree–Fock estimates. Ab initio models of the ring currents induced by a magnetic field normal to the molecular plane were obtained for the three isomeric systems of higher symmetry, showing that the π electrons give rise to intense diamagnetic circulation. The π currents are responsible for enhanced magnetic anisotropy and strong out-of-plane proton deshielding. The theoretical findings are used to build up a “diatropicity …

ProtonAb initioMagnetic Susceptibility ; Current Density ; Nuclear Screening ; Isomerism ; HF Calculations ; Ab Initio Calculations ; Magnetic Fields ; Magnetic Anisotropy ; Organic CompoundsGeneral Physics and AstronomyHF CalculationsMagnetic SusceptibilityMolecular physicsFuro-furan Isomers; Magnetizability and Nuclear Magnetic ShieldingFuro-furan IsomersIsomerismAb initio quantum chemistry methodsMagnetizability and Nuclear Magnetic ShieldingPhysical and Theoretical Chemistry:FÍSICA::Química física [UNESCO]Condensed matter physicsOrganic CompoundsChemistryNuclear ScreeningMagnetic susceptibilityMagnetic AnisotropyMagnetic fieldUNESCO::FÍSICA::Química físicaMagnetic anisotropyMagnetic FieldsElectromagnetic shieldingDiamagnetismCurrent DensityAb Initio Calculations
researchProduct