Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1985-1989  (9)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Determinant based configuration interaction algorithms for complete and restricted configuration interaction spaces (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2185-2192 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A restricted active space (RAS) wave function is introduced, which encompasses many commonly used restricted CI expansions. A highly vectorized algorithm is developed for full CI and other RAS calculations. The algorithm is based on Slater determinants expressed as products of alphastrings and betastrings and lends itself to a matrix indexing C(Iα, Iβ ) of the CI vector. The major features are: (1) The intermediate summation over determinants is replaced by two intermediate summations over strings, the number of which is only the square root of the number of determinants. (2) Intermediate summations over strings outside the RAS CI space is avoided and RAS calculations are therefore almost as efficient as full CI calculations with the same number of determinants. (3) An additional simplification is devised for MS =0 states, halving the number of operations. For a case with all single and double replacements out from 415 206 Slater determinants yielding 1 136 838 Slater determinants each CI iteration takes 161 s on an IBM 3090/150(VF).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455063
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A multiconfigurational self-consistent reaction-field method (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3086-3095 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present theory and implementation for a new approach for studying solvent effects: the multiconfigurational self-consistent reaction-field (MCSCRF) method. The atom, molecule, or supermolecule is assumed to be surrounded by a linear, homogeneous, continuous medium described by its macroscopic dielectric constant. The electronic structure of the compound is described by a multiconfigurational self-consistent field (MCSCF) wave function. The wave function is fully optimized with respect to all variational parameters in the presence of the surrounding polarizable dielectric medium. We develop a second-order convergent optimization procedure for the solvent states. The solvent integrals are evaluated by an efficient and general algorithm. The flexible description of the electronic structure allows us to accurately describe ground, excited, or ionized states of the solute. Deficiencies in the calculation can therefore be assigned to the cavity model rather than the description of the solute.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454965
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Erratum: Second-order Møller–Plesset perturbation theory as a configuration and orbital generator in multiconfiguration self-consistent-field calculations [J. Chem. Phys. 88, 3834 (1988)] (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5354-5354 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455749
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Self-consistent reaction field calculations of photoelectron binding energies for solvated molecules (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6422-6435 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiconfigurational self-consistent reaction field (MCSCRF) and the self-consistent reaction field (SCRF) methods are applied for solvation shifts of molecular photoelectron spectra. Calculations are performed for cavity wave functions of water, benzene, methanol, and formamide surrounded by dielectric continua corresponding to various solvents. The cavity wave functions for single- or multiconfigurational closed- and open-shell states are optimized self-consistently with their reaction fields, using either a continuum approach with one solute molecule embedded in the dielectric medium or a semicontinuum approach with one solute molecule and a solvation shell of molecules surrounded by the dielectric medium. The application of the MCSCRF/SCRF model gives new insight into the effects of a solvent on ionization spectra. The origin of both absolute and differential shifts upon solvation is investigated. This includes studies of local vs delocalized ionization, role of dielectric polarization vs reaction field contributions to the solvation shift, optical vs static dielectric response of the medium, and use of noncorrelated vs correlated solute wave functions. It is found that the use of the semicontinuum model with one solvation shell is often crucial to obtain experimental agreement. Comparatively large multipolar expansions of the solute charge distribution is often needed to adequately treat the solvent interaction. The results for differential core–valence and core–core shifts lead to some interesting observations that can be further explored using photoelectron and soft x-ray spectroscopic techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456308
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Second-order Møller–Plesset perturbation theory as a configuration and orbital generator in multiconfiguration self-consistent field calculations (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3834-3839 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown that the magnitude of the natural orbital (NO) occupation numbers of second-order Møller–Plesset (MP2) perturbation theory can be used to select physically reasonable configuration spaces for ground state MCSCF calculations. When the MP2 NO's are used as an initial guess for the orbitals, a second-order Newton–Raphson MCSCF calculation is in the local region from the first iteration. Fast convergence is therefore ensured to a stationary point with orbitals of similar structure as the MP2 NO's, thereby reducing significantly the risk of converging to undesired stationary points.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453884
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Efficient optimization of large scale MCSCF wave functions with a restricted step algorithm (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 451-466 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Auxiliary algorithms for efficient optimization of large scale MCSCF wave functions are devised and implemented in a previously developed direct, second order, restricted step MCSCF program. As demonstrated by the numerical examples, these algorithms drastically reduce the computation time. We also demonstrate efficient optimization of excited states with "root flipping'' and of core hole states without variational collapse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453590
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Systematic determination of MCSCF equilibrium and transition structures and reaction paths (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 3917-3929 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The restricted step optimization algorithm is applied to potential energy surfaces calculated from multiconfiguration self-consistent-field wave functions. Equilibrium and transition-state geometries are determined by iteratively solving a set of level-shifted Newton–Raphson equations. At each geometry the molecular gradient and Hessian are calculated analytically, and a first-order prediction of the wave function at the next geometry is obtained by combining the geometrical derivatives of the wave function with the geometrical step vector. The usefulness of this prediction is discussed and illustrated by test calculations. The numerical accuracy which is required in the wave function and its geometrical derivatives in order to maintain quadratic convergence in the optimization of the molecular geometry is analyzed. It is demonstrated that the Newton–Raphson step vector and the wave function prediction may be determined without calculating the molecular Hessian explicitly. Sample calculations are carried out for the potential energy surfaces of diazene (N2H2) and the diazenyl radical (N2H). Equilibrium geometries are determined in less than five iterations and the optimization of transition states requires typically ten iterations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450914
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Analytical calculation of MCSCF dipole-moment derivatives (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 6280-6284 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The analytical calculation of molecular dipole-moment derivatives for MCSCF wave functions is described. The formalism is based on exponential unitary transformation of the wave function and symmetric orthonormalization of the molecular orbitals. The response equations are solved using an iterative, direct technique to allow for large configuration expansions. Translational and rotational symmetries of the dipole moment are used to minimize computational costs. Sample calculations involving several thousand configurations are presented for H2O and ONF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450772
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Molecular Hessians for large-scale MCSCF wave functions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 6266-6279 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The calculation of molecular Hessians for large-scale multiconfiguration self-consistent-field (MCSCF) functions is described. The formalism is based on exponential parametrization of the wave function and symmetric orthonormalization of the molecular orbitals. Extensive use is made of one-index transformations of the molecular integrals, both to construct the gradient vectors that appear in the linear MCSCF response equations, and to perform the multiplication of the trial vectors on the electronic Hessian in the iterative, direct solution of the response equations. No element of the electronic Hessian is ever calculated explicitly, allowing for use of large configuration expansions. Efficient methods are developed for obtaining the solution vectors of the linear response equations. The accuracy of the molecular Hessian is analyzed in terms of the accuracy of these solution vectors. To allow for large basis sets Fock matrices are used to minimize transformations and integrals are recalculated to minimize storage requirements. Integral derivatives are calculated following the McMurchie–Davidson scheme. A simplified algorithm for calculation of derivatives of integrals involving one-center overlap distributions is described. Sample calculations involving several thousand configurations are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450771
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...