First-principle study on structural, linear and nonlinear optical properties of selenocyanate complex ZnCd(SeCN)4 crystal

Abstract

Bimetallic selenocyanate complex ZnCd(SeCN)4 (ZCSC) crystals are a novel material with ultraviolet nonlinear optical (NLO) properties. To the best of our knowledge, theoretical studies on these complexes have mostly focused on the microcosmic NLO responses of single complex molecular system and ignored their macroscopic NLO effects. In this paper, the geometric structure of ZCSC crystal was optimized on the basis of first principle, and the electronic band structure and linear optical (LO) properties were investigated via pseudopotential plane wave method. The macroscopic NLO properties of ZCSC crystal were evaluated through the combination of density functional theory and a devised anionic group method for the first time, and good agreement with the experimental results was obtained. The absorption spectrum of ZCSC was located at 95–325 nm, and the NLO properties were mainly caused by the transitions of electronic states from N2p and Se3p valence bands to C2p, N2p, Se3p, and Cd4p conduction bands. Results showed that the second-order NLO coefficients were d14 = 2.304–3.55 pm/V and d15 = 8.07–9.91 pm/V, showing an evident increase compared with those of ZnCd(SCN)4 crystals.