Search results for " ab initio calculations."

showing 3 items of 13 documents

Rovibrational structure of the Ar–CO complex based on a novel three-dimensional ab initio potential

2002

The first three-dimensional ab initio intermolecular potential energy surface of the Ar–CO van der Waals complex is calculated using the coupled cluster singles and doubles including connected triples model and the augmented correlation-consistent polarized valence quadruple zeta (aug-cc-pVQZ) basis set extended with a (3s3p2d1f1g) set of midbond functions. The three-dimensional surface is averaged over the three lowest vibrational states of CO. Rovibrational energies are calculated up to 50 cm−1 above the ground state, thus enabling comprehensive comparison between theory and available experimental data as well as providing detailed guidance for future spectroscopic investigations of highe…

Potential Energy SurfacesCoupled Cluster CalculationsAb initioGeneral Physics and AstronomyPhysics and Astronomy (all)symbols.namesakeAb initio quantum chemistry methodsQuasimoleculesPhysics::Atomic and Molecular ClustersVibrational StatesPhysics::Atomic PhysicsPhysics::Chemical PhysicsPhysical and Theoretical ChemistryArgon:FÍSICA::Química física [UNESCO]Rotational-Vibrational StatesBasis setValence (chemistry)ChemistryRotational–vibrational spectroscopyCarbon CompoundsUNESCO::FÍSICA::Química físicaCoupled clustersymbolsArgon ; Carbon Compounds ; Quasimolecules ; Rotational-Vibrational States ; Potential Energy Surfaces ; Ab Initio Calculations ; Intermolecular Mechanics ; Coupled Cluster Calculations ; Vibrational StatesIntermolecular Mechanicsvan der Waals forceAtomic physicsGround stateAb Initio Calculations
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Computational and experimental investigation of intermolecular states and forces in the benzene-helium van der Waals complex

2003

A study of the intermolecular potential-energy surface (IPS) and the intermolecular states of the perprotonated and perdeuterated benzene–He complex is reported. From a fit to ab initio data computed within the coupled cluster singles and doubles including connected triples model for 280 interaction geometries, an analytic IPS including two- to four-body atom–atom terms is obtained. This IPS, and two other Lennard-Jones atom–atom surfaces from the literature, are each employed in dynamically exact (within the rigid-monomer approximation) calculations of J = 0 intermolecular states of the isotopomers. Rotational constants and Raman-scattering coefficients for intermolecular vibrational trans…

Potential Energy SurfacesCoupled Cluster CalculationsRaman SpectraHelium Neutral AtomsOrganic Compounds ; Helium Neutral Atoms ; Intermolecular Mechanics ; Quasimolecules ; Potential Energy Surfaces ; Ab Initio Calculations ; Coupled Cluster Calculations ; Lennard-Jones Potential ; Isotope Effects ; Isomerism ; Rotational States ; Raman SpectraAb initioGeneral Physics and AstronomyIsotopomerssymbols.namesakePhysics and Astronomy (all)IsomerismAb initio quantum chemistry methodsQuasimoleculesKinetic isotope effectPhysics::Atomic and Molecular ClustersRotational StatesPhysics::Atomic PhysicsLennard-Jones PotentialPhysics::Chemical PhysicsPhysical and Theoretical Chemistry:FÍSICA::Química física [UNESCO]ChemistryOrganic CompoundsIsotope EffectsIntermolecular forceUNESCO::FÍSICA::Química físicaCoupled clusterLennard-Jones potentialsymbolsIntermolecular MechanicsAtomic physicsvan der Waals forceAb Initio Calculations
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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
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