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Parity violation (PV) effects to the electronic ground state structure for a series of chiral tungsten molecules of the type NWXYZ (X, Y, Z=H, F, Cl, Br, or I) are compared using four- (Dirac) and two- (X2C) component relativistic Hartree–Fock and density functional theories. The results show the computationally more affordable two-component X2C approach yields accurate results for all molecules investigated. The PV energy differences between the two enantiomers range from as little as 0.4 Hz for NWClBrI to 140 Hz for NWHClI using a generalized gradient approximation including exact exchange (B3LYP). The W[Single_Bond]N stretching mode in these molecules lies in the experimentally favorable CO2 laser frequency range, and we therefore investigated PV effects in vibrational transitions using a single normal mode analysis. Here the PV frequency shift between the two enantiomers ranges from 1.6 mHz for NWFBrI to 710 mHz for NWHClI. Thus these types of molecules could be useful for the future detection of PV effects in chiral molecules. [ABSTRACT FROM AUTHOR]

The potential energy curve of the electronic ground state of the mercury dimer based on CCSD(T) calculations at the complete basis set (CBS) limit, including corrections for the full triples ΔT and explicit spin-orbit (SO) interactions at the CCSD(T) level of theory, is presented. In the far long-range part, the potential energy curve is complemented by symmetry-adapted perturbation theory calculations. Potential curves of an analytically simple, extended Lennard-Jones form are obtained from very accurate fits to the CBS/CCSD(T)+SO and CBS/CCSD(T)+SO+ΔT data. The Hg2 potential curves yield dissociation energies of De=424/392 cm-1 and equilibrium distances of re=3.650/3.679 Å at the CBS/CCSD(T)+SO and CBS/CCSD(T)+SO+ΔT levels of theory, respectively. By including perturbative quadruple corrections in our coupled-cluster calculations and corrections from correlating the 4f-core, we arrive at a final dissociation energy of De=405 cm-1, in excellent agreement with the experimentally estimated value of 407 cm-1 by Greif and Hensel. In addition, the rotational and vibrational spectroscopic constants as well as the second virial coefficient B(T) in dependence of the temperature T are calculated and validated against available experimental and theoretical data. [ABSTRACT FROM AUTHOR]

New relativistic energy-consistent pseudopotentials have been generated for the 5d transition metals Hf–Pt. The adjustment was done in numerical two-component multiconfiguration Hartree–Fock calculations, using atomic valence-energy spectra from four-component multiconfiguration Dirac–Hartree–Fock calculations as reference data. The resulting two-component pseudopotentials replace the [Kr]4d104f14 cores of the 5d transition metals and can easily be split into a scalar-relativistic and a spin-orbit part. They reproduce the all-electron reference energy data with deviations of ∼0.01 eV for configurational averages and ∼0.05 eV for individual relativistic states. Full series of correlation consistent basis sets from double to quintuple-zeta have also been developed in this work for use with the new pseudopotentials. In addition, all-electron triple-zeta quality correlation consistent basis sets are also reported in order to provide calibration for the pseudopotential treatment. The accuracy of both the pseudopotentials and basis sets are assessed in extensive coupled cluster benchmark calculations of atomic ionization potentials, electron affinities, and selected excitation energies of all the 5d metal atoms, including the effects of spin-orbit coupling. [ABSTRACT FROM AUTHOR]

Parity violation (PV) effects for a series of chiral molecules of the type SeOXY (X,Y=H, F, Cl, Br, or I) are predicted from four-component relativistic Hartree–Fock and density functional theory. All optimized SeOXY structures are nonplanar with large inversion barriers ranging from 23 to 55 kcal/mol; thus, all SeOXY molecules remain enantiomeric stable on the laboratory time scale. The variation in PV between the different methods applied is small enough for each molecule to allow for an accurate prediction of these effects. At the respective equilibrium geometries the enantiomers exhibit parity violating energy shifts of up to 17 Hz. The Se–O stretching mode of all investigated SeOXY molecules lies in the experimentally favorable CO2 laser range of ∼1000 cm-1. We therefore investigated PV effects in vibrational transitions along a single normal mode using Dirac–Kohn–Sham theory. The PV energy differences in the fundamental Se–O stretching mode amount up to 110 mHz (largest for SeOClI) and are larger compared to the C–F stretching mode of CHFBrI previously investigated. Hence these SeOXY molecules are ideal candidates for the future experimental gas-phase detection of PV in vibrational spectra of chiral molecules. [ABSTRACT FROM AUTHOR]

Recently reported energy-consistent relativistic pseudopotentials have been used with series of matching correlation consistent basis sets in benchmark calculations of various atomic and molecular properties. The basis set convergence of the 4d metal electron affinities and 5s2→5s0 excitation energies are reported at the CCSD(T) level of theory, and the effects of valence and 4s4p correlation are investigated. In addition the impact of correlating the low-lying 3d electrons was also studied in all-electron Douglas-Kroll-Hess (DKH) calculations, which also included the ionization potentials and 5s2→5s1 excitation energies. For all four atomic properties, higher order coupled cluster calculations through CCSDTQ are reported. The final calculated values are generally all within 1 kcal/mol of experiment. A notable exception is the ionization potential of Tc, the currently accepted experimental value of which is suggested to be too high by about 3 kcal/mol. Molecular calculations are also reported for the low-lying electronic states of ZrO and RuF, as well as the ground electronic state of Pd2. The effects of spin-orbit coupling are investigated for these cases in pseudopotential calculations. Wherever possible, the pseudopotential results have been calibrated against DKH calculations with correlation consistent basis sets of triple-zeta quality. In all cases the calculated data for these species are in very good agreement with experiment. In particular, the correct electronic ground state for the RuF molecule (4[uppercase_phi_synonym]9/2) was obtained, which was made possible by utilizing systematic sequences of correlation consistent basis sets. [ABSTRACT FROM AUTHOR]

The four-component atomic intermediate-Hamiltonian Fock-space coupled cluster (IHFSCC) code of Landau et al. [J. Chem. Phys. 115, 6862 (2001)] has been adapted to two-component calculations with relativistic pseudopotentials of the energy-consistent variety. Recently adjusted energy-consistent pseudopotentials for group 11 and 12 transition elements as well as group 13 and 14 post-d main group elements, which were fitted to atomic valence spectra from four-component multiconfiguration Dirac-Hartree-Fock calculations, are tested in IHFSCC calculations for ionization potentials, electron affinities, and excitation energies of a variety of atoms and ions. Where comparison is possible, the deviations from experimental data are in good agreement with those found in previously published IHFSCC all-electron calculations: experimental data are usually reproduced within a few hundred wavenumbers. [ABSTRACT FROM AUTHOR]

Scalar-relativistic pseudopotentials and corresponding spin-orbit potentials of the energy-consistent variety have been adjusted for the simulation of the [Ar]3d10 cores of the 4d transition metal elements Y–Pd. These potentials have been determined in a one-step procedure using numerical two-component calculations so as to reproduce atomic valence spectra from four-component all-electron calculations. The latter have been performed at the multi-configuration Dirac-Hartree-Fock level, using the Dirac-Coulomb Hamiltonian and perturbatively including the Breit interaction. The derived pseudopotentials reproduce the all-electron reference data with an average accuracy of 0.03 eV for configurational averages over nonrelativistic orbital configurations and 0.1 eV for individual relativistic states. Basis sets following a correlation consistent prescription have also been developed to accompany the new pseudopotentials. These range in size from cc-pVDZ-PP to cc-pV5Z-PP and also include sets for 4s4p correlation (cc-pwCVDZ-PP through cc-pwCV5Z-PP), as well as those with extra diffuse functions (aug-cc-pVDZ-PP, etc.). In order to accurately assess the impact of the pseudopotential approximation, all-electron basis sets of triple-zeta quality have also been developed using the Douglas-Kroll-Hess Hamiltonian (cc-pVTZ-DK, cc-pwCVTZ-DK, and aug-cc-pVTZ-DK). Benchmark calculations of atomic ionization potentials and 4dm-25s2→4dm-15s1 electronic excitation energies are reported at the coupled cluster level of theory with extrapolations to the complete basis set limit. [ABSTRACT FROM AUTHOR]

The equilibrium structure and the harmonic and anharmonic force fields of BiH3 are determined by high-level ab initio calculations using a variety of correlation treatments, basis sets, and pseudopotentials, partly in combination with core polarization potentials. Spin—orbit effects are included by a configuration interaction treatment. This systematic study serves to establish a reliable computational protocol for such calculations and, in particular, to minimize basis set superposition errors through an improved new basis set and/or counterpoise corrections. Using the recommended procedures, the best ab initio results for the equilibrium geometry and the fundamental vibrational wave numbers are in good agreement with the available experimental data, which further supports the recent spectroscopic identification of BiH3 . The ground-state total atomization energy of BiH3 is predicted to be 153.1 kcal/mol. [ABSTRACT FROM AUTHOR]

A series of correlation consistent basis sets have been developed for the post-d group 16–18 elements in conjunction with small-core relativistic pseudopotentials of the energy-consistent variety. The latter were adjusted to multiconfiguration Dirac–Hartree–Fock data based on the Dirac–Coulomb–Breit Hamiltonian. The outer-core (n-1)spd shells are explicitly treated together with the nsp valence shell with these PPs. The accompanying cc-pVnZ-PP and aug-cc-pVnZ-PP basis sets range in size from DZ to 5Z quality and yield systematic convergence of both Hartree–Fock and correlated total energies. In addition to the calculation of atomic electron affinities and dipole polarizabilities of the rare gas atoms, numerous molecular benchmark calculations (HBr, HI, HAt, Br[sub 2], I[sub 2], At[sub 2], SiSe, SiTe, SiPo, KrH[sup +], XeH[sup +], and RnH[sup +]) are also reported at the coupled cluster level of theory. For the purposes of comparison, all-electron calculations using the Douglas–Kroll–Hess Hamiltonian have also been carried out for the halogen-containing molecules using basis sets of 5Z quality. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The spectroscopic and thermochemical properties of the halogen monoxides and their anions are investigated by using high-level electronic structure calculations. The inclusion of full iterative triple and quadruple excitations in the coupled cluster treatment is very important for obtaining high level of accuracy.

The scaled quantum mechanical procedure (SQM) and transferable scaling factors (TSF) have been determined for a set of natural internal coordinates involving bromine and iodine atoms resulting to energy-consistent relativistic pseudopotentials adjusted to multiconfiguration Dirac-Hartree-Fock atomic. Thus these TSFs are tailored for the use with new MCDHF-adjusted seven-valence-electron energy-consistent pseudopotentials for Br and I and comparison with experimental data is found to be excellent.

Preliminary theoretical results, cited by Meloni and Gingerich in the title paper, are supplemented by new information (a) on the structure of the SnBi[sub 2] molecule, and (b) on computed atomization energies for SnBi[sub n] (n=1–3). © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Small but mighty: An unprecedented large parity-violation energy difference of 0.7 Hz for the N-W stretching frequency of N≡WHClI, which conveniently lies in the CO(2) laser frequency range, is predicted from relativistic density functional theory. This result could lead to the first successful detection of such effects in chiral molecules., (Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)