THEORETICAL-STUDIES OF THE ELECTRONIC-STRUCTURES AND LINEAR, NONLINEAR OPTICS OF K3-XLI2+XNB5O15 WITH X=0 AND X=1

The electronic structures of the ground state have been calculated usi ng the IDO/1-SCl method, and in combination with the sum-over-states m ethod, the first and second frequency dependent polarizabilities have been obtained for microscopic species of K3-xLi2+xNb5O15 with x = 0 an d x = 1. The calculated birefringences delta n and phase matching nonl inear optical coefficients d(31) indicate that the K3-xLi2+xNb5O15 wit h higher lithium content will enhance nonlinear optical effects at the fundamental wavelengths of 1064 and 820 nm. The charge transfer state s formed from oxygen atomic 2p orbitals with a mixing of niobium atomi c 4d character to alkali metal atomic valence orbitals with mixing of niobium 5s, 5p character make the most significant contributions to th e susceptibility.