A theoretical investigation of hyperpolarizability for small GanAsm (n+m=4–10) clusters

In this paper, the second and third order polarizabilities of small GanAsm (n+m=4–10) clusters are systematically investigated using the time dependent density functional theory (TDDFT)∕6-311+G* combined with the sum-over-states method (SOS∕∕TDDFT∕6-311+G*). For the static second order polarizabilities, the two-level term (βvec.2) makes a significant contribution to the βvec for all considered GanAsm clusters except for the Ga3As4 cluster. And, for the static third order polarizabilities, the positive channel (⟨γ⟩II) makes a larger contribution to ⟨γ⟩tot than the negative channel (⟨γ⟩I). Similar to the cubic GaAs bulk materials, the small GanAsm cluster assembled materials exhibit large second order (1×10−6esu) and third order susceptibilities (5×10−11esu). The dynamic behavior of β(−2ω;ω,ω) and γ(−3ω;ω,ω,ω) show that the small GanAsm cluster will be a good candidate of nonlinear optical materials due to the avoidance of linear resonance photoabsorption.