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  • Computational Chemistry and Molecular Modeling
  • 1
    Electronic Resource
    Electronic Resource
    A Crystal Orbital approach for two- and three-dimensional solids on the basis of CNDO/INDO Hamiltonians. Basis equations (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 47-71 
    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: A Hartree-Fock (HF) self-consistent field (SCF) crystal orbital (CO) formalism for two- and three-dimensional (2D/3D) solids on the basis of semiempirical CNDO/INDO (complete neglect of differential overlap; intermediate neglect of differential overlap) Hamiltonians is presented. The employed SCF variants allow for the treatment of atomic species up to bromine under the inclusion of the first (i.e., 3d) transition metal series. Band structure investigations of 2D and 3D materials containing more than 30 atoms per unit cell are feasible by the present SCF HF CO formalism. The theoretical background of the computational scheme is given in this contribution. Special emphasis is placed on physically reliable truncation criteria for the lattice sums, the adaptation of the crystal symmetry in k space, as well as the suitable choice of domains in Brillouin zone (BZ) integrations required in the determination of charge-density matrices. The capability and limitations of the semiempirical SCF HF CO approach is demonstrated for some simpler solids by comparing the present computational results with those of ab initio CO schemes as well as conventional numerical methods in soid-state theory. The employed model solids are graphite and BN (2D and 3D networks for both solids) as well as diamond, silicon, germanium, and TiS2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340107
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  • 2
    Electronic Resource
    Electronic Resource
    The use of symmetry in reciprocal space integrations. Asymmetric units and weighting factors for numerical integration procedures in any crystal symmetry (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 571-594 
    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: A systematic collection of spatial domains for reciprocal space integrations is derived for all possible crystal symmetries. This set can be used as a simpler alternative to the conventional Brillouin zones. The analysis is restricted to integrations where the function in the integrand satisfies inversion symmetry in k space. In this case only 24 different spatial domains have to be defined in order to allow for k space integrations in the 230 different crystal symmetries. A graphic representation of the asymmetric unit for each of the 24 integration domains is given. Special positions and the associated weighting factors required for numerical integrations in theoretical solid-state approaches are tabulated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340609
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical study of the interaction of Ga. Ga+, and Ga2+ with the hydrogen molecule (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 781-791 
    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 C2v, potential energy curves for the interaction of Ga, Ga+, and Ga2+ with the hydrogen molecule were calculated using the pseudopotential method of Durand et al. and triple-ζ gaussian basis sets. Electronic correlation has been taken into account by MRCI + MP2 calculations. We studied the 2B2(4p), 2A1(4p), 2A1(5s), and 2B2(5p) surfaces for the Ga + H2, the 1A1, 3B2, and 1B2 surfaces for Ga+ + H2 and the 2A1,(4s), 2B2, and 2A1(5s) surfaces for the Ga2+ + H2 reaction. We first analyzed the unrelaxed H2 approach to the metallic center, followed by the angle relaxation. The reactivity in all the interactions studied are analyzed with a model mechanism, previously proposed by us. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440869
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical study of the reaction of Cd(1S, 3P, 1P) with the methane molecule (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 587-598 
    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 reaction pathways of the interaction of the methane molecule with the cadmium atom in the ground state (1S) and the two lowest excited states (3P, 1P) were determined using Hartree-Fock followed by multireference configuration interaction plus second-order multireference Möller-Plesset calculations. No spontaneous activation of the methane molecule was observed by these electronic states of the cadmium atom due to the existence of activation barriers of 107.2, 27, and 17.3 kcal/mol, respectively. The geometry and electronic structure of the HCdCH3 intermediate molecule and the CdH and CdCH3 products involved in the reaction were also determined, as well as the dissociation pathway of HCdCH3 towards the CdH + CH3 and H + CdCH3 products. We found that the HCdCH3 intermediate reaches the final products without any barriers and also that the initial reactants in the ground state need to be provided with 88.5 kcal/mol to obtain the CdH + CH3 products and with 99.8 kcal/mol to get the H + CdCH3 products. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480853
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical study of the rhodium dimer interaction with the hydrogen molecule (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 549-557 
    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 C2v potential energy surfaces for the end-on and side-on approaches of H2 to the rhodium dimer were studied through self-consistent-field (SCF) and multiconfigurational SCF calculations, followed by extensive variational plus second-order multireference Møller-Plesset perturbational configuration interaction (CIPSI) calculations. Relativistic effective core potentials were used to replace the core electrons of the rhodium atoms. Together with the Rh2—H2 interaction, the spectroscopic constants for the 5Σg+, 1Σg+, 3Πu, and 1Πu states of Rh2 are reported. We found that the potential energy curves of the parallel and the perpendicular Rh2(5Σg) interaction with H2 show that the rhodium dimer has the ability to capture and break the H2 molecule. The parallel interaction presents a soft potential barrier of 7.8 kcal/mol, energy necessary to surmount before the capture and breaking of the H—H bond. In the perpendicular interaction, we found that Rh2 captures and breaks spontaneously H2. The potential energy curve of the parallel Rh2(1Σg) + H2 interaction shows that Rh2 also captures and breaks spontaneously the H2, with a very deep well of 92.7 kcal/mol, while in the perpendicular approach, we found that Rh2 has to surmount again a soft barrier of 5.2 kcal/mol to capture and break the H2 molecule. Finally, the energy curves of the parallel (Rh2(1,3Πu) + H2) interactions present capture and breaking with very small barriers. The perpendicular interactions capture and scisse the hydrogen molecule spontaneously. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560858
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  • 6
    Electronic Resource
    Electronic Resource
    The two-dimensional band structure of (polyphthalocyaninato)Ni(II) (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 73-84 
    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 two-dimensional (2D) band structure of (polyphthalocyaninato)Ni(II), Ni(ppc), has been analyzed by a self-consistent field (SCF) Hartree-Fock (HF) crystal orbital (CO) formalism based on an INDO (intermediate neglect of differential overlap) type Hamiltonian. The calculated HF band gap of Ni(ppc) amounts to 0.24 eV. The highest filled band is a ringlike a1u combination (D4h symmetry label) localized at the carbon sites of the organic fragment. Remarkable hybridization in the valence band leads to the considerable band width Δ∊v of 2.92 eV. This value is close to the Δ∊v numbers which are conventionally encountered in one-dimensional metallomacrocycles. The effective width of the states in Ni(ppc) is 13.8 eV. In graphite a net π interval of 13.0 eV is predicted by the present CO formalism; i.e., the energetic distribution of the π electrons is roughly comparable in both 2D solids. The Ni 3d states in Ni(ppc) are far below the Fermi level which is calculated at -4.9 eV; they are predicted between -12.2 and -16.4 eV in the mean-field approximation. Quasi-particle corrections lead to a significant shift of these strongly metal-centered states. Important electronic structure properties of Ni(ppc) are compared with those of 1D metallomacrocycles with similar molecular stoichiometry. The total density of states distribution of Ni(ppc) has been fragmented into projected (ligand π and σ, Ni 3d) contributions in order to allow for a transparent interpretation of the 2D band structure.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340108
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  • 7
    Electronic Resource
    Electronic Resource
    Calculation of integrals with slater basis from the one-range expansion of the 0s function (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 69-83 
    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: A one-range expansion of the 0s-STO - previously reported by us - is employed to derive explicit expressions for the elements of auxiliary matrices - appearing in the calculation of one- and two-electron multicenter integrals with STOS - in the form of infinite series. Then, we are able to perform the formal summation of the series giving both closed expressions for these elements and several relations between them. A computational algorithm based on these formal developments is proposed and its numerical behavior is analyzed.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370106
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  • 8
    Electronic Resource
    Electronic Resource
    Calculation of two-center exchange integrals with STOs using Möubius transformations (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 11-19 
    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 Möbius transformations recently proposed for integrating functions with a sharp peak close to a single boundary of integration (H.H.H. Homeier and E.O. Steinborn, J. Comput. Phys. 87, 61, 1990) are used to extend Ruedenberg's algorithm for two-center exchange integrals to cases with very diffuse STOs. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560490103
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  • 9
    Electronic Resource
    Electronic Resource
    Improved algorithm for the calculation of one-electron two-center integrals with STOs (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 869-874 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In a previous article (J. Fernández Rico, R. López and G. Ramírez, J. Comp. Chem., 9, 790 (1988)) we have proposed the calculation of molecular integrals involving STOs by means of some recurrence relations which use two sets (h and H) of overlap integrals (basic matrices). In the present paper, we derive explicit expressions of these integrals employing the two-range expansion of the 0s-function. This approach yields equations for the elements of the two basic matrices in terms of two further matrices, k(x,y) and i(x,y), and some auxiliary functions. Relations between the elements of these matrices and the functions are thoroughly explored and numerical tests are included for illustrating the behavior of the method.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540100703
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  • 10
    Electronic Resource
    Electronic Resource
    Transferable semiempirical quadratic force fields: The case of polythiophene and shorter oligomers (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 405-423 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The vibrational spectra of oligomers of thiophene are treated theoretically with the main purpose of deriving information for the interpretation of the infrared and Raman spectra of the polymer and isotopic derivatives. We report the results of a series of semiempirical MNDO calculations on the structure and vibrational properties of oligothiophenes, and we compare the calculated MNDO Pulay scaled force field of the monomer with an empirical harmonic force field that we have obtained by least squares refinement on nine isotopic derivatives. The scaling factors obtained were transferred from thiophene for the computation of the vibrational spectrum and the phonon dispersion curves of the polymer. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150405
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