Richard Jarman - Approaches to understanding Structure-Property Relationships in Nonlinear Optical Materials

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      Publication Details (including relevant citation   information):

      Approaches to   understanding Structure-Property Relationships in Nonlinear   Optical Materials, R.H. Jarman, M. Munowitz and J.F. Harrison, J.   Crystal Growth, 109, 353 (1991).

      Abstract:

        Ab initio calculations of the electronic structure of   TiO6    octahedra are used to provide some insight into the nonlinear   optical properties of KTP (potassium titanyl phosphate) crystals.   Such octahedra tield doubly charged anions which, when abstracted   from the unit cell, are stable relative to the isolated atoms   once hydrogen are attached to the four oxygens normally   coordinated to phosphorus. Initial results suggest that at least   two configurations may contribute to the ground-state electronic   structure. In the configuration with lowest energy, the two   highest occupied molecular orbitals establish weak dπ-pπ bonds   between titanium and an oxygen located unusually close to the   metal. The next orbital shows a a bond between the titanium and   the nearby oxygen, while the distant (trans) oxygen remains   nonbonded. In the second configuration, the π bond is absent but   there is a significant transfer of charge between the two oxygens   trans to Ti(2) in the -O-Ti-O-Ti- chains, with the shift effected   through a d-p σ bond. Optical properties of KTP and related   systems also are investigated experimentally by photoelectron   spectroscopy and SHG (second harmonic generation) measurements on   powders.

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