Research Interests

    1. Theory of conducting polymers
         We are interested in understanding the optical and electronic
    properties of quasi one dimensional conjugated polymers from a
    basic theoretical point of view. For model calculations, tight
    binding models involving electron-electron interactions are
    considered. Various many-body methods are employed to solve
    for the electronic and lattice structures in the ground state as well
    as the excited states. For a representative reference, please see the
    papers in Physical Review Letters, Vol. 74, 1167(1995) and in
    Springer Series in Solid State Sciences, Vol. 124, 121(1997).

2. The X-ray phase problem

Structure of [SnClGe{Si(CH₃)₃]₄. Pink, Blue, Green, Brown and Gray correspond to Sn, Ge, Cl, Si and C respectively.

        A fundamental problem in X-ray crystallography is to invert the
    diffraction data to determine the atomic positions in the crystals. We
    have been pursuing a new approach to solve this problem. An initial
    random guess of the atomic positions is gradually improved (by
    employing the technique of simulated annealing) until a sensible
    structure emerges. We have recently solved a molecular structure
    which has defied existing methods. Please refer to the paper in
    Acta Crystallographica A, Vol. 53, 396(1997).

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