Dynamic second-order hyperpolarizabilities of Si3 and Si4 clusters using coupled cluster cubic response theory

The dynamic second-order hyperpolarizabilities γ of Si3 and Si4 clusters have been first calculated using the highly accurate coupled cluster cubic response theory. At ω = 0.43 au (1064 nm), the dynamic γ values of the Si3 and Si4 clusters are 46.26 × 10−36 and 92.50 × 10−36 esu, respectively. The dynamic γ values of the Si3 and Si4 clusters exhibit wide non-resonant optical region (ω < 0.04 au). The magnitude of macroscopic second-order hyperpolarizabilities χ(3)(−3ω; ω, ω, ω) is of the order of 10−12 esu at ω < 0.04 au. Small Si clusters might be good candidates for nonlinear optical materials in infrared range.