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  • 1985-1989  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Ab initio configuration interaction study of the electronic and geometric structure of small, mixed neutral and cationic MgNak and MgLik (k=2–8) clusters (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4229-4241 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutral and cationic MgYk clusters with Y=Na, Li (k=2–8) have been investigated using all-electron ab initio configuration interaction (CI) procedures. The alkaline earth metal (or group IIa) atom takes the central position in the most stable geometries of all clusters studied except for MgNa3, MgLi3, and MgNa+3 . The importance of the chemical nature of the atoms involved in determining the stability and other properties of the clusters, is clearly demonstrated by comparing the neutral and cationic series of MgNak , MgLik , and BeLik . The properties obtained can be fully explained by considering the s–p promotion, the role of Jahn–Teller distortions, and the stereochemical aspects. The appropriate treatment of electronic correlation effects is of crucial importance for correctly predicting the stability of the clusters. The low stability of small clusters, especially MgNak (k〈5), is particularly noticeable. The atomization energies per atom for MgY6, MgY7, and MgY8 with Y=Na or Li, are all found to be comparable. The general pattern for atomization energies per atom and for other stability measures as well as for fragmentation channels and ionization potentials as functions of the cluster size is explained in the paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456802
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ab initio configuration-interaction study of the photoelectron spectra of small sodium cluster anions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3794-3795 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We find that the ab initio direct configuration-interaction calculations on Na−2–5 and Na2–5 account for the observed patterns of photoelectron spectra, reproduce the observed excitation energies in a semiquantitative way and permit an assignment of cluster geometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456862
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular bonding with scandium: Diatomics ScH, ScO, ScC, and ScN (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3747-3760 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spectroscopic and chemical properties of some typical diatomics of scandium are calculated using a nonempirical HF pseudopotential and multireference single-and-double configuration interaction. The potential energy curves of ScO, where the ground state (2∑+) is clearly separated from other low-lying states (2Δ,2Π, and 4Π), are in good agreement with experimental data, and the strong bonding is paralleled with a significant ionic nature. All six lowest states (1∑+,3∑+,1Π,3Π,1Δ, and 3Δ) of ScH dissociating into the ground state atoms have a common bonding orbital and they can only be distinguished from each other by the orbital(s) used by the two nonbonding Sc electrons and their relative spin dispositions. The ScC molecule has about the same stability as ScH with respect to dissociation of the ground state, but the former shows a more complicated bonding nature in its lowest states (2∑+,2Π,2Δ,4∑−,4∑+,4Π, and 4Δ). Highly degenerate bound states 5Δ,5Π, and 3∑− of ScN appear to be the least bonding among the heteronuclear diatomics studied here. The estimated binding energies obtained from these calculations are about 2.0 eV for ScH and ScC, and 1.0 eV for ScN. The different characteristics of the lowest Sc atomic states which are due to different 3d and 4s occupations are analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453874
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  • 4
    Electronic Resource
    Electronic Resource
    General properties of the electronic structure of alkali metal clusters and Ia-IIa mixed clusters (1989)
    Springer
    The European physical journal 12 (1989), S. 307-314 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.D ; 31.30 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of the systematic ab-initio CI investigation of neutral and charged Li n , Na n , BeLi k and MgNa k clusters are summarized and analyzed. The general characteristic features of the electronic structure are pointed out:a) The participation of the atomic orbitals, which are empty in Ia and IIa metal atoms, allows for a higher valency of these atoms in clusters.b) Jahn-Teller and pseudo-Jahn-Teller effects strongly influence the electronic and geometric structure of clusters.c) Deformations of cluster geometry can lead to biradicaloid structures with higher spin multiplicity in their ground states.d) The peculiarities of the electronic structures of clusters can be deduced from the presence of many “surface” atoms. The theoretical results agree with experimental data presently available and they are useful for interpretation of the experimental findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426963
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  • 5
    Electronic Resource
    Electronic Resource
    General principles governing structures of small clusters (1986)
    Springer
    The European physical journal 3 (1986), S. 147-153 
    Details
    ISSN: 1434-6079
    Keywords: 7300
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract General rules which govern electronic and geometric structures of small clusters are formulated, and their validity is documented with the results of the MRD - CI investigations for Li n , BeLi k , Be l (n=2−14,k=2−6,l=2−13) as well as on IIa and IVa tetramers. The MRD - CI results are compared with investigations performed with other methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384800
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  • 6
    Electronic Resource
    Electronic Resource
    Core-valence correlation potentials based on density functional theory. Applications to valence-electron-only calculations on Na and K diatomics (1989)
    Springer
    The European physical journal 13 (1989), S. 355-361 
    Details
    ISSN: 1434-6079
    Keywords: 31.20 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The core-valence correlation potential has been derived for Na and K employing atomic calculations which make use of the density functional formula worked out by Lee, Yang and Parr based on Colle-Salvetti approach. The numerical potential is fitted with a small number of Gaussians leading to a very simple expression for an one-electron corevalence correlation operatorŴ cv . The core-valence correlation corrections can be computed by applyingŴ cv on a quite general class of wavefunctions. Applications of theŴ cv operator within the framework of valence-electron-only calculations using effective Hamiltonians are presented for Na and K atoms, for Na2, K2, NaK and their cations. Almost all the corrections calculated for the physical properties due to the core-valence correlation lead to results which are in good agreement with those obtained from much more sophisticated treatments and experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01398902
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  • 7
    Electronic Resource
    Electronic Resource
    Usefulness of modified virtual orbitals in multireference CI procedure illustrated by calculations on lithium clusters (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 6 (1985), S. 462-468 
    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 maximization of the exchange interaction between the canonical Hartree-Fock virtual and occupied orbitals leads to a transformed set of virtual orbitals which are well suited as one-electron functions for CI calculations. The procedure, generally known for a long time is seldom applied, despite its simplicity and very low computational demand. However, it is found to be particularly useful in the case of multireference CI, since an improved energy is obtained with a considerable shortening of the CI expansion. Moreover, in the final CI wave function, several configurations appear with considerable weight, thus allowing an easy choice of additional configurations to be inserted in the definition of a new zero-order wave function. The efficiency of the computational procedure is discussed for the case of a Li6 cluster of D3h symmetry and for the NaCO and PdCO complexes. Results are reported for the relative stability of four different geometrical arrangements of the Li6 cluster.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540060515
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