Richard Jarman - Theoretical Study of the Nonlinear Optical Properties of KTiOPO4: Effects of T-O-Ti Bond Angles and Oxygen Electronegativity

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      Publication Details (including relevant citation   information):

      Theoretical   Study of the Nonlinear Optical Properties of KTiOPO4:   Effects of T-O-Ti Bond Angles and Oxygen Electronegativity, M.   Munowitz, R.H. Jarman and J.F. Harrison, Chem. Mater.,   5, 1257   (1993).


      Second harmonic generation in the model system   [TiO5--TiO6--TiO5]20- is studied using a

      perturbative sum-over-states formalism together with extended   Huckel wave functions. The

      nonlinear response of the central TiO6 group, a distorted   octahedron with its fourfold axis

      defined by the atoms O1--Ti--O2, improves both with increasing   Ti--O--Ti angle and with

      decreasing electronegativity of the chain oxygens. A small shift   of charge toward the distant

      oxygen, O1, takes place as the Ti--O--Ti angle is increased,   thereby enlarging the electronic third

      moment and with it the local hyperpolarizability. Reducing the   electronegativity of the oxygens,

      by contrast, brings about a near-resonant enhancement of the   hyperpolarizability, which occurs

      as energies of the highest occupied molecular orbitals are   raised. These results are placed in

      the context of recent experimental measurements involving   compounds isomorphic to KTiOPO4.

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