Publication Details (including relevant citation information):
Theoretical Study of the Nonlinear Optical Properties of KTiOPO4: an Extended Huckel/Sum-Over-States Approach, M. Munowitz, R.H. Jarman and J.F. Harrison, Chem. Mater., 4, 1296 (1992).
We investigate, within the framework of extended Huckel theory, the origins and structural dependences
of the electronic hyperpolarizability tensors of asymmetric TiO2 and TiO68-. The TiO68- species, which
is a basic structural unit of KTiOPO4 (KTP), is taken as a distorted octahedron with the trans oxygens
placed asymmetrically above and below the TiO4 equatorial plane. A term-by-term analysis of the per-
turbative series for both TiO2 and TiO68- shows that second harmonic generation derives predominantly
from A excitations (relative to the asymmetric O-Ti-O axis) and that the net hyperpolarizability results
from the near cancellation of large contributions with opposite signs. Specific contributions to the hy-
perpolarizability, which we classify into three major π families and three major σ families, typically pass
through minima and maxima as the difference between long and short Ti-O bonds is increased.
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