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  • Computational Chemistry and Molecular Modeling  (4)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 29 (1986), S. 793-797 
    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: We report local-density functional results for the electronic structure of neutral soliton defects in polyacetylene. The results were obtained using a modified version of the discrete variational method Xα molecular cluster model. For defect-free chains the calculated X-ray and ultraviolet photoelectron spectra are in good agreement with experiment. For chains with low concentrations of solitons, we find the forbidden gap broadens slightly, and two nearly dispersionless bands, split by several tenths of eV, are introduced into the gap. The predicted splitting is in accord with recent experimental results for this defect.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 131-136 
    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: Most band structure calculations approximate the integral over the Brillouin zone of momentum (i.e., wave vector) dependent properties with an appropriately weighted sum over a discrete set of points in the Brillouin zone. The best choice for such a set of points has long been a point of discussion in crystalline band structure calculations. For one-dimensionally periodic systems, however, the usual choice of points has been evenly spaced points in the one-dimensional Brillouin zone with equal weights. We have analyzed the exact error for the integral over the π band of a tight-binding model of trans-polyacetylene as a function of bond alternation. We find that the error in π band energy decreases in magnitude as q-2, where q is the total number of points treated in the Brillouin zone, for the metallic polyacetylene system with equal bond lengths. As bond alternation increases, however, we find that the error in π band energy decreases in magnitude roughly exponentially as a function of bond alternation for any given value of q. We find that this systematic change in error as a function of bond alternation can lead to either apparent overestimation or underestimation of the equilibrium dimerization and stabilization energy of Peierls distorted systems using first-principles total energy calculations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 549-555 
    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 propagation of nonlinear waves induced by a shock impulse in a linear atomic chain of finite but large length is investigated numerically with a model interatomic potential. The shock impulse is initiated by giving the first atom in the chain an initial velocity vi toward its neighbor. We find that there exists a velocity vc such that for vi 〉 vc a soliton is produced by this impulse with a constant energy and supersonic velocity vs. Studies of the motion of the atom during the passage of this soliton reveal a behavior similar to that expected from the collision of hard spheres. However, for vi 〈 vc the induced pulse propagates below the speed of sound and gradually disperses through the emission of phonons. In the supersonic regime, vi 〉 vc, we find that there exists a velocity vm such that if vi 〉 vm, then vs 〈 vi, but if vi 〈 vm, then vs 〉 vi. Finally, in agreement with earlier studies using other model potentials, we find that if vi is large enough, a soliton can be generated with sufficient energy to spall an atom from the end of the chain.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 129-137 
    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: Molecular dynamics simulations are used to study hypervelocity impacts of an ultrathin flyer plate with a semi-infinite two-dimensional model diatomic molecular solid. We show that these hypervelocity impacts can produce a dissociative phase transition from a molecular to a close-packed solid in the target material. We also show that hypervelocity impacts of ultrathin plates can produce extensive chemical reactions leading to a detonation accompanied by a phase transition in an energetic version of the model. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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