Remarkable second-order optical nonlinearity of nano-sized Au20 cluster: a TDDFT study

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 (βxyz) calculated to be 14.3 × 10−30 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.