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Hydrogen bonding in long chains of hydrogen fluoride and long chains and large clusters of water molecules (1974)

Karpfen, Alfred ; Ladik, Janos ; Russegger, Peter ; [et al.]

Springer

Theoretical chemistry accounts 34 (1974), S. 115-127

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ISSN: 1432-2234

Keywords: (HF)n-chains ; (H2O)n-chains ; Hydrogen bond energies

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Energy band structures of one-dimensional (HF)n- and (H2O)n-chains have been calculated (1) by extrapolation of CNDO/2-MO levels to infinite chain length and (2) by the CNDO/2 crystal orbital (CO) method. In the CO-calculations interactions up to fifth neighbours have been taken into account. Both types of calculations were performed using experimental geometries and CNDO/2 minimum geometries of the corresponding dimers (HF)2 and (H2O)2. With the same geometries CO calculations on two-dimensional sheets of hydrogen bonded chains were performed too. Due to end-effects the extrapolated MO bands are much broader than the bands obtained by the CO method. In the CO calculations further neighbour interactions play a non-negligible role and hence the nearest neighbour approximation is not sufficient for an accurate description of crystals containing hydrogen bonds. MO calculations on one-dimensional chains of both systems show that the hydrogen bond energies increase with the number of monomers indicating the presence of cooperative effects. The hydrogen bond energies calculated with the CO method are usually somewhat larger than those extrapolated from the MO results. In three-dimensional networks of (H2O)n, however, the additional stabilization of clusters with respect to dimers is drastically diminished.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00551362

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New implementation of a program to calculate correlated band structures of polymers: An application to the band structure of polyparaphenylene (PPP) (1994)

Palmer, Ian J. ; Ladik, Janos

New York, NY [u.a.] : Wiley-Blackwell

Journal of Computational Chemistry 15 (1994), S. 814-819

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ISSN: 0192-8651

Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Computer Science

Notes: A new program has recently been implemented with the aim of extending quasi-particle (QP) band structure calculations to polymers with larger unit cells. The theoretical background is briefly reviewed and the new algorithm described, which has been optimized for machines with vector processors. To illustrate the usefulness of this technique, calculations have been performed on polyparaphenylene (PPP) using a double-zeta basis set. The calculated QP band gap between the valence and conduction bands is 2.3 eV, which compares favorably with the experimental value of 2.8 eV. The self-consistent field (SCF) result with the same double-zeta basis set is 8.7 eV. © 1994 by John Wiley & Sons, Inc.

Additional Material: 1 Ill.