Publication Details (including relevant citation information):
Electronic Structure of Ti(OH)4O2-: A Model for Potassium Titanyl Phosphate, M. Munowitz, R.H. Jarman and J.F. Harrison, J. Phys. Chem., 96, 124 (1992).
Ab initio studies of axially distorted TiO6 octahedra are used to simulate electronic structure in a system similar to potassium
titanyl phosphate (KTP), a material noted for its strong nonlinear optical properties. The C4 model system, Ti(OH)4O22-,
consists of a planar Ti(OH)4 unit plus O- ions directly above and below the titanium at the center. Two of the possible electronic
states are identified: the first, with A symmetry, arising when the oxygen p(σ) orbitals along the O-Ti-O axis are only partially
occupied; the second, a B state, arising when these orbitals are filled. In the A state, electrons are able to flow from one
axial oxygen to another through an in-phase combination of p(σ) orbitals on the oxygens and the dz2 on the metal. When
the two oxygens are not equidistant from the titanium, this mechanism is able to generate a charge asymmetry significantly
out of proportion to the geometric distortion. In the B state, by contrast, charge transfer through the σ system is largely
precluded since the oxygen p(σ) orbitals are filled. The equivalent pathway is instead through the π system, where the transfer
from one set of partially occupied oxygen p(π) orbitals to the other can be mediated by d(π) orbitals on the titanium. Compared
to the σ conduit in the A state, however, the movement of charge between the two oxygens is less dramatic and less sensitive
to variations in internuclear distance.
Address (URL): http://