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 using the INDO/1-SCI method, and in combination with the sum-over-states method, the first and second frequency dependent polarizabilities have been obtained for microscopic species of K3−xLi2+xNb5O15 with x = 0 and x = 1. The calculated birefringences δn and phase matching nonlinear optical coefficients d31 indicate that the K3−xLi2+xNb5O15 with higher lithium content will enhance nonlinear optical effects at the fundamental wavelengths of 1064 and 820 nm. The charge transfer states formed from oxygen atomic 2p orbitals with a mixing of niobium atomic 4d character to alkali metal atomic valence orbitals with mixing of niobium 5s, 5p character make the most significant contributions to the susceptibility.