Search results for "Complete basis set limit"

showing 4 items of 4 documents

On the convergence of zero-point vibrational corrections to nuclear shieldings and shielding anisotropies towards the complete basis set limit in wat…

2016

The method and basis set dependence of zero-point vibrational corrections (ZPVCs) to nuclear magnetic resonance shielding constants and anisotropies has been investigated using water as a test system. A systematic comparison has been made using the Hartree–Fock, second-order Møller–Plesset perturbation theory (MP2), coupled cluster singles and doubles (CCSD), coupled cluster singles and doubles with perturbative triples corrections (CCSD(T)) and Kohn–Sham density functional theory with the B3LYP exchange-correlation functional methods in combination with the second-order vibrational perturbation theory (VPT2) approach for the vibrational corrections. As basis sets, the correlation consisten…

waterBiophysicsZero-point energyzero-point vibrational correctionMonotonic function010402 general chemistry01 natural sciencesQuantum mechanics0103 physical sciencesPhysics::Atomic and Molecular ClustersCCSD(T)Limit (mathematics)complete basis set limitPhysics::Chemical PhysicsPhysical and Theoretical ChemistryMolecular BiologyBasis setPhysics010304 chemical physicsBasis (linear algebra)Condensed Matter PhysicsNMR shielding constant0104 chemical sciencesCoupled clusterDensity functional theoryPerturbation theory (quantum mechanics)Molecular Physics
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Extrapolation of water and formaldehyde harmonic and anharmonic frequencies to the B3LYP/CBS limit using polarization consistent basis sets

2010

The harmonic and anharmonic frequencies of fundamental vibrations in formaldehyde and water were successfully estimated using the B3LYP Kohn-Sham limit. The results obtained with polarization- and correlation-consistent basis sets were fitted with a two-parameter formula. Anharmonic corrections were obtained by a second order perturbation treatment (PT2). We compared the performance of the PT2 scheme on the two title molecules using SCF, MP2 and DFT (BLYP, B3LYP, PBE and B3PW91 functionals) methods combined with polarization consistent pc-n (n = 0, 1, 2, 3, 4) basis sets, Dunning’s basis sets (aug)-cc-pVXZ where X = D, T, Q, 5, 6 and Pople’s basis sets up to 6-311++G(3df,2pd). The influence…

ExtrapolationPerturbation (astronomy)Sensitivity and SpecificityVibrationMolecular physicsCatalysisInorganic ChemistryRoot mean squareFormaldehydeQuantum mechanicsWavenumberIR and Raman theoretical spectraPhysics::Chemical PhysicsPhysical and Theoretical ChemistryBasis setOriginal PaperChemistrySpectrum AnalysisOrganic ChemistryAnharmonicityHarmonicReproducibility of ResultsWaterComplete basis set limitModels TheoreticalPolarization (waves)Computer Science ApplicationsVibrationComputational Theory and MathematicsAnharmonicJournal of Molecular Modeling
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Estimation of formamide harmonic and anharmonic modes in the Kohn-Sham limit using the polarization consistent basis sets.

2010

Formamide harmonic and anharmonic frequencies of fundamental vibrations in the gas phase and in several solvents were successfully estimated in the B3LYP Kohn-Sham complete basis set limit (KS CBS). CBS results were obtained by extrapolating a power function (two-parameter formula) to the results calculated with polarization-consistent basis sets. Anharmonic corrections using the second order perturbation treatment (PT2) and hybrid B3LYP functional combined with polarization consistent pc-n (n = 0, 1, 2, 3, 4) and several Pople’s basis sets were analyzed for all fundamental formamide vibrational modes in the gas phase and solution. Solvent effects were modeled within a PCM method. The anhar…

FormamideAcetonitrilesMolecular ConformationAnharmonic vibrationSolvent effectMolecular physicsCatalysisInorganic ChemistryAcetonechemistry.chemical_compoundComputational chemistryScissoringHexanesComputer SimulationDimethyl SulfoxideHarmonic vibrationPhysical and Theoretical ChemistryPhysics::Chemical PhysicsCarbon TetrachlorideBasis setQuantitative Biology::BiomoleculesOriginal PaperFormamidesOrganic ChemistryAnharmonicityWaterComplete basis set limitFormamideComputer Science ApplicationsComputational Theory and MathematicschemistryModels ChemicalMolecular vibrationHarmonicSolventsThermodynamicsFermi resonanceChloroformGasesSolvent effectsJournal of molecular modeling
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Prediction of water's isotropic nuclear shieldings and indirect nuclear spin–spin coupling constants (SSCCs) using correlation‐consistent and polariz…

2009

Density functional theory (DFT) was used to estimate water's isotropic nuclear shieldings and indirect nuclear spin-spin coupling constants (SSCCs) in the Kohn-Sham (KS) complete basis set (CBS) limit. Correlation-consistent cc-pVxZ and cc-pCVxZ (x = D, T, Q, 5, and 6), and their modified versions (ccJ-pVxZ, unc-ccJ-pVxZ, and aug-cc-pVTZ-J) and polarization-consistent pc-n and pcJ-n (n = 0, 1, 2, 3, and 4) basis sets were used, and the results fitted with a simple mathematical formula. The performance of over 20 studied density functionals was assessed from comparison with the experiment. The agreement between the CBS DFT-predicted isotropic shieldings, spin-spin values, and the experimenta…

Coupling constantSOPPA(CCSD)Condensed matter physicsChemistryIsotropywaterKohn–Sham equationsPropagatorspin–spin coupling constantsGeneral ChemistryPolarization (waves)DFT‐NMRnuclear isotropic shieldingsSSCCSOPPAGeneral Materials ScienceDensity functional theoryAtomic physicscomplete basis set limitSpin (physics)Basis setMagnetic Resonance in Chemistry
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