PNNL

Abstract

The dipole polarizability, static first hyperpolarizability, and UV-vis spectrum of the recently identified nano-sized tetrahedral cluster of Au20 have been investigated by using time-dependent density functional response theory. We have discovered that the Au20 cluster possesses remarkably large molecular second-order optical nonlinearity with the first hyperpolarizabilty ( ßxyz) calculated to be 14.3 x 10?³° electrostatic unit (esu). The analysis of the low-energy absorption band suggests that the charge transfer from the edged gold atoms to the vertex ones plays the key role in nonlinear optical (NLO) response of Au20.