Pulsed response theory prediction of ZnO nanocluster polarizabilities: A benchmark study

Motivated by the interest in zinc oxide nanostructures and their properties, we calculate in this work molecular polarizabilities and hyperpolarizabilities of a series of zinc oxide nanoclusters using modern response theory in the form of damped and pulsed response for both Hartree-Fock and DFT reference states. We show that as the size of the cluster grows, both real and imaginary parts of polarizability, computed with these two distinct approaches, asymptotically converge. We also show the importance of eliminating the dangling bonds in small clusters for predicting the correct trend in the values of the HOMO/LUMO gap. Finally, we calculate the hyperpolarizability tensors, associated with the second order nonlinear optical effects, in the hexagonal (wurtzite) phase of ZnO nanoclusters and demonstrate a highly nonlinear growth of this quantity with the cluster size.