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  • 1
    Electronic Resource
    Electronic Resource
    Electronic structure and electric properties of the alkali metal dimers (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 9692-9704 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dipole moments and dipole polarizabilities of a series of the alkali metal atom dimers involving Li, Na, K, and Rb are calculated at the level of different coupled cluster approximations as well as the complete active space self-consistent-field approach followed by the perturbation treatment of the dynamical correlation effects. All reported calculations have been carried out with recently developed polarized basis sets. The electron correlation effects on these electric properties are studied within the valence and valence plus next-to-valence shell approximations. Also the relativistic contribution is calculated by using the quasirelativistic scalar (mass–velocity+Darwin terms) approximation. A comparison of results of different methods indicates that the values calculated by the coupled clusters method in which one- and two-electron clusters are treated iteratively and the three-body terms perturbatively [as defined in the CCSD(T) method] are well saturated in terms of the electron correlation contribution to molecular electric properties of the dimers. The achieved agreement with available experimental data is for most molecules fairly good. The interpretation of the electric property data is based on the analysis of the valence and core-polarization contributions and the observed regularities are elucidated in terms of simple molecular orbital ideas. The dipole moments of the heteronuclear dimers follow the pattern predicted by electronegativities of the two atoms. The perpendicular component of the electric dipole polarizability has been found to mostly reflect its atomlike origin, while the parallel one is intimately related to the electronic structure of the week bonding in the dimers. The relativistic effect becomes of certain importance only for the rubidium compounds. The results of our calculations are compared with ab initio and empirical pseudopotential data and with more recent calculations using the density functional theory methods. Our results indicate that the density functional methods lead to fairly reliable polarizability data, though they depend on the choice of the exchange and exchange-correlation potentials. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469984
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  • 2
    Electronic Resource
    Electronic Resource
    Polarized basis sets for high-level-correlated calculations of molecular electric properties (1996)
    Springer
    Theoretical chemistry accounts 93 (1996), S. 101-129 
    Details
    ISSN: 1432-2234
    Keywords: Polarized basis sets ; Dipole polarizabilities of Cu, Ag, and Au ; Dipole polarizabilities of Cu+, Ag+, and Au+ ; Relativistic effects on atomic electric properties ; Electron correlation effects on atomic electric properties ; Relativistic ; correlation corrections ; SA CCSD(T) method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The first-order polarized basis sets PolMe are generated for elements (Me=Cu, Ag, Au) of group Ib of the periodic table by using the basis set polarization method developed in earlier papers. The performance of these basis sets is extensively tested in calculations of atomic dipole polarizabilities with particular attention given to the evaluation of the electron correlation and relativistic contributions. The extension by theg-type polarization functions (PolMe-g sets) is devised for use in accurate calculations of atomic and molecular electric properties. The (negative) electron correlation contribution to dipole polarizabilities of all elements of group Ib, as calculated at the level of the spin adapted coupled cluster method with single and double excitations and non-iterative corrections for the contribution of the T3 clusters (SA CCSD(T)), remains at the same level relative to the ROHF data. The pure relativistic correction to the ROHF results, evaluated within the quasirelativistic approximation involving the mass-velocity and Darwin corrections, is negative and rapidly increases with increase of the nuclear charge. Its large negative value is, for heavier systems, partly compensated by a positive contribution from the mixed relativistic-correlation terms. Our relativistically corrected SA CCSD(T) calculations predict the following values of the dipole polarizability in the coinage metal series: 46, 51, and 29 a.u., for Cu, Ag, and Au. The present results for Cu and Ag agree well with recent pseudopotential calculations by Schwerdtfeger and Bowmaker. However, for Au our result is by about 6 a.u. lower than that obtained by using 19-electron relativistic potentials. Several possible reasons for this discrepancy are discussed. The PolMe and PolMe-g basis sets are also used to calculate electric dipole polarizabilities of the singly positive ions of group Ib elements. The results obtained in the quasirelativistic CCSD(T) approximation are 6.6, 9.2, and 11.8 a.u. for Cu+, Ag+, and Au+, respectively. These values follow the pattern expected for the series of ions whose polarizability is dominated by the next-to-valenced shell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113551
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  • 3
    Electronic Resource
    Electronic Resource
    CCSD(T) expectation value calculations of first-order properties (1997)
    Springer
    Theoretical chemistry accounts 98 (1997), S. 75-84 
    Details
    ISSN: 1432-2234
    Keywords: Key words: CCSD(T) expectation value calculations ; First-order properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. An expectation value approach to calculations of first-order properties using the non-iterative, triple-excitation amplitudes in the coupled cluster wave function is exploited. Three methods are suggested and analysed using the many body perturbation theory (MBPT) expansion arguments. The first method, in which non-iterative triple-excitation amplitudes are used in the expression for the expectation values, makes the wave function accurate through the second order of MBPT. In the second method, which is an extension of the first, effects of triple-excitation amplitudes are coupled with single- and double-excitation amplitudes. The correlated density matrix equivalent through the fourth order to that obtained when CCSDT-la amplitudes are used is employed in the third method. The suggested methods are tested on dipole moment and polarizability calculations for several diatomic closed-shell molecules and are compared to other related approaches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050282
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  • 4
    Electronic Resource
    Electronic Resource
    Accurate electrical and spectroscopic properties ofX 1Σ+ BeO from coupled-cluster methods (1995)
    Springer
    Theoretical chemistry accounts 90 (1995), S. 341-355 
    Details
    ISSN: 1432-2234
    Keywords: BeO molecule ; Coupled-cluster calculations ; Quadratic configuration interaction ; Spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper reports a series of coupled-cluster (CC) calculations through CCSDT on the theoretically challenging ground state of the BeO molecule. Along with CC methods, quadratic configuration interaction (QCI) approximations to CC theory have been used (QCISD and QCISD(T)), which show several dramatic failings. Equilibrium electrical properties (μ, α xx , and α zz ) and basic spectroscopic properties (r e, θe,D e, and infrared intensity (I)) have been computed. Basis set and electron correlation effects are analyzed in order to arrive at accurate values of the dipole moment and polarizability, which are not known experimentally. For the dipole moment, we obtain a value of 6.25 D, with an uncertainty of about 0.1 D. For α xx and α zz , we suggest respective values of 32 and 36 atomic units (a.u.) and error bars of about 1 and 2 a.u. With extended basis sets, the spectroscopic propertiesr e, θe, andD e are reproduced to high accuracy, which is the first time this has been achieved for this species byab initio methods. At the highest calculation levels,I is predicted to be very small. AlthoughI has not been measured, some support for this prediction comes from a recent infrared study of BeO-rare gas complexes. The QCI methods are shown to be much more sensitive to basis set, and even with large basis sets yield values of α zz andI which differ from CC results by an order of magnitude and three orders of magnitude, respectively. These differences doubtless arise from the importance of single excitations (T 1) for this molecule, as several terms involvingT 1 are neglected in the QCISD approximation compared with CCSD. We also report CC calculations with Brueckner orbitals, which yield results similar to those obtained with restricted Hartree-Fock orbitals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113541
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  • 5
    Electronic Resource
    Electronic Resource
    Accurate electrical and spectroscopic properties of X1Σ+ BeO from coupled-cluster methods (1995)
    Springer
    Theoretica chimica acta 90 (1995), S. 341-355 
    Details
    ISSN: 0040-5744
    Keywords: Key words: BeO molecule ; Coupled-cluster calculations ; Quadratic configuration interaction ; Spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  This paper reports a series of coupled-cluster (CC) calculations through CCSDT on the theoretically challenging ground state of the BeO molecule. Along with CC methods, quadratic configuration interaction (QCI) approximations to CC theory have been used (QCISD and QCISD(T)), which show several dramatic failings. Equilibrium electrical properties (μ, α xx , and α zz ) and basic spectroscopic properties (r e, ωe, D e, and infrared intensity (I)) have been computed. Basis set and electron correlation effects are analyzed in order to arrive at accurate values of the dipole moment and polarizability, which are not known experimentally. For the dipole moment, we obtain a value of 6.25 D, with an uncertainty of about 0.1 D. For α xx and α zz , we suggest respective values of 32 and 36 atomic units (a.u.) and error bars of about 1 and 2 a.u. With extended basis sets, the spectroscopic properties r e, ωe, and D e are reproduced to high accuracy, which is the first time this has been achieved for this species by ab initio methods. At the highest calculation levels, I is predicted to be very small. Although I has not been measured, some support for this prediction comes from a recent infrared study of BeO–rare gas complexes. The QCI methods are shown to be much more sensitive to basis set, and even with large basis sets yield values of α zz and I which differ from CC results by an order of magnitude and three orders of magnitude, respectively. These differences doubtless arise from the importance of single excitations (T 1) for this molecule, as several terms involving T 1 are neglected in the QCISD approximation compared with CCSD. We also report CC calculations with Brueckner orbitals, which yield results similar to those obtained with restricted Hartree–Fock orbitals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113541
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  • 6
    Electronic Resource
    Electronic Resource
    Polarized basis sets for high-level-correlated calculations of molecular electric properties VII. Elements of the group Ib: Cu, Ag, Au (1996)
    Springer
    Theoretica chimica acta 93 (1996), S. 101-129 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Polarized basis sets ; Dipole polarizabilities of Cu ; Ag ; and Au ; Dipole polarizabilities of Cu+ ; Ag+ ; and Au+ ; Relativistic effects on atomic electric properties ; Electron correlation effects on atomic electric properties ; Relativistic ; correlation corrections ; SA CCSD(T) method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  The first-order polarized basis sets PolMe are generated for elements (Me=Cu, Ag, Au) of group Ib of the periodic table by using the basis set polarization method developed in earlier papers. The performance of these basis sets is extensively tested in calculations of atomic dipole polarizabilities with particular attention given to the evaluation of the electron correlation and relativistic contributions. The extension by the g-type polarization functions (PolMe-g sets) is devised for use in accurate calculations of atomic and molecular electric properties. The (negative) electron correlation contribution to dipole polarizabilities of all elements of group Ib, as calculated at the level of the spin adapted coupled cluster method with single and double excitations and non-iterative corrections for the contribution of the T3 clusters (SA CCSD(T)), remains at the same level relative to the ROHF data. The pure relativistic correction to the ROHF results, evaluated within the quasirelativistic approximation involving the mass–velocity and Darwin corrections, is negative and rapidly increases with increase of the nuclear charge. Its large negative value is, for heavier systems, partly compensated by a positive contribution from the mixed relativistic–correlation terms. Our relativistically corrected SA CCSD(T) calculations predict the following values of the dipole polarizability in the coinage metal series: 46, 51, and 29 a.u., for Cu, Ag, and Au. The present results for Cu and Ag agree well with recent pseudopotential calculations by Schwerdtfeger and Bowmaker. However, for Au our result is by about 6 a.u. lower than that obtained by using 19-electron relativistic potentials. Several possible reasons for this discrepancy are discussed. The PolMe and PolMe-g basis sets are also used to calculate electric dipole polarizabilities of the singly positive ions of group Ib elements. The results obtained in the quasirelativistic CCSD(T) approximation are 6.6, 9.2, and 11.8 a.u. for Cu+, Ag+, and Au+, respectively. These values follow the pattern expected for the series of ions whose polarizability is dominated by the next-to-valence d shell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113551
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  • 7
    Electronic Resource
    Electronic Resource
    Spin-Adapted restricted Hartree-Fock reference coupled-cluster theory for open-shell systems: Noniterative triples for noncanonical orbitals (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 187-203 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupled clusters singles and doubles (CCSD) method for calculations of open-shell systems with the single restricted Hartree-Fock (ROHF) reference determinant is extended by the noniterative triples to give CCSD(T). Our approach profits from the fact that (a) single- and double-excitation amplitudes are spin-adapted, which directly leads to a computationally less demanding algorithm than are nonadapted procedures and produces the spin-adapted CCSD wave function and (b) triple excitations calculated from converged spin-adapted (SA) CCSD amplitudes are also obtained more effectively. Altogether, computer demands of our SA CCSD(T) approach, applicable to high-spin open-shell cases which are well represented by a single-determinant reference is comparable to that for closed-shell systems. Our approach is not based on semicanonical orbitals, applied by Bartlett's group. However, we compare some other possible choices of ROHF orbitals to this “standard.” Numerical results for a series of atoms and molecules demonstrate little sensitivity to this selection. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560550214
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  • 8
    Electronic Resource
    Electronic Resource
    Introduction (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 75-75 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560550202
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  • 9
    Electronic Resource
    Electronic Resource
    Ionization potentials and electron affinities of Cu, Ag, and Au: Electron correlation and relativistic effects (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 557-565 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron correlation and relativistic effects on ionization potentials and electron affinities of Cu, Ag, and Au are investigated in the framework of the coupled cluster method and different 1-component approximations to the relativistic Dirac-Coulomb Hamiltonian. The first-order perturbation approach based on the massvelocity and Darwin terms is found to be sufficiently accurate for Cu and Ag while it fails for Au. The spin-averaged Douglas-Kroll no-pair method gives excellent results for the studied atomic properties. The ionization potentials obtained within this method and the coupled cluster scheme for the electron correlation effects are 7.733(7.735) eV for Cu, 7.461(7.575) eV for Ag, and 9.123(9.225) eV for Au (experimental values given in parentheses). The calculated (experimental) electron affinity results for Cu, Ag, and Au are 1.236(1.226), 1.254(1.303), and 2.229(2.309) eV, respectively. There is a marked relativistic effect on both the ionization potential and electron affinity of Ag which sharply increases for Au while Cu exhibits only a little relativistic character. A similar pattern of relativistic effects is also observed for electric dipole polarizabilities of the coinage metal atoms and their ions. The coupled cluster dipole polarizabilities of the coinage metal atoms calculated in this article in the Douglas-Kroll no-pair formalism (Cu: 46.50 au; Ag: 52.46 au; Au: 36.06 au) are compared with our earlier data for their singly positive and singly negative ions. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 557-565, 1997
    Additional Material: 5 Tab.
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  • 10
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    Relativistic coupled-cluster static dipole polarizabilities of the alkali metals from Li to element 119 (1999)
    American Physical Society
    Details
    Publication Date: 1999-10-01
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Physical Society
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