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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4442-4452 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Predictions of the diatomics-in-ionic-systems model for the variety of stationary points on the potential energy surfaces of the hydrogen fluoride clusters (HF)n (3≤n≤6) are compared to the results of ab initio MP2/6-311+G(2d,2p) calculations as well as to the results of the polarizable mechanics model of Hodges et al. [J. Phys. Chem. A 102, 2455 (1998)]. The diatomics-in-ionic-systems scheme which relies on the balanced treatment of neutral and ionic contributions to the electronic properties of polyatomic species within the diatomics-in-molecules theory takes into account here the mixing of the FH and F−H+ electronic states. The corresponding mixing coefficient serves as a single principal adjustable parameter of the model, finally selected by the reference value of the binding energy of (HF)3. It is shown that structures and energies of the main cyclic isomers are in a good agreement with the best estimates of Quack and Suhm [Conceptual Perspectives in Quantum Chemistry (Kluwer, Dordrecht, 1997)]. Every prediction of this model for the stationary points corresponding to 16 higher energy structures of (HF)n is confirmed by the MP2 ab initio data.© 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2638-2647 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Further developments of the intermolecular diatomics-in-molecules (DIM) theory towards construction of potential energy surfaces of hydrogen-bonded molecular aggregates are presented. Compared to the previously studied hydrogen fluoride clusters (HF)n [J. Chem. Phys. 111, 4442 (1999)], considerably more complicated and challenging systems, namely, water clusters (H2O)n (n=2–6) have been analyzed in this work. The present DIM, or more precisely, diatomics-in-ionic-systems, scheme is based on the balanced treatment of neutral and ionic contributions to the electronic properties of polyatomic species, and in this case takes into account the mixing of the OH and O−H+ electronic states within the valence bond description of water molecules. The potential curves of diatomic molecules required for the present application, including ionic species O−H, OH+, O2−, have been computed by ab initio quantum chemistry tools. The results of DIM calculations of equilibrium geometry configurations, binding energies, and relative energies for the low-lying isomers of (H2O)n (n=2–6) are compared to the reference data showing a good predictive power of this method. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 513-521 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A hybrid quantum mechanical diatomics-in-molecules (QM/DIM) method is formulated that aims to describe chemical reactions in an environment within the framework of a discrete (or cluster) approach. Starting from the conventional DIM formalism, first-order intermolecular perturbation theory is applied to calculate interactions between reacting particles and environmental molecules, and to introduce ab initio QM energies for the central system. In this approach no boundary problems appear when combining two parts of the entire system. The pairwise contributions to the interaction energy come from the true potential curves of the fragments. A proper treatment of excited electronic states is also provided in this approach. As a first application, we compute potential curves for the dissociation reaction of a single hydrogen fluoride molecule surrounded by a selected number of solvent HF molecules. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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