High-quality semi-organic and inorganic complex crystal material can generate highly efficient second harmonic blue-violet light by using GaAlAs laser diodes, which has attracted considerable fundamental and technological interest. Based on the growth of urea and metal organometallic complex nonlinear optical crystal material, the transition metal thiourea complexes crystal, Hg(SCN2H4)4Zn(SCN)4 (TMTZ), is designed.In this kinds of materials, there is asophisticated coordination structure for double metal thiourea ligand, and the nonlinear effects is also involved the d-d electron interactions. So the micro-structure, electron transfer, and relationship between structure and macroscopic optical properties, have not been investigated as far as we known. Therefore, it is urgent essay to have an insight into the nonlinear optical mechanism. In the present paper, the quantum-mechanical calculations based on the density functional theory(DFT) and pseudopotential method are used to study the structural, electronic, linear optical properties of TMTZ. The SHG coefficients have been calculated using anionic group theory. According to the optimized structure, the band structure, DOS and PDOS of TMTZ crystal were calculated. TMTZ crystal has obvious direct bandgap structural feature and the bandgap value is 3.14 eV. Combining with PDOS. It was found that H1s，C2p, N2p and S3p orbitals have obvious hybrid, which is the main source of the second-order NLO effect. The bond populations and electron density projection were calculated, and it was concluded that the S–C，C–N and N-H bonds show stronger covalency, and Zn–N and Hg–S bonds exhibit strong ionicity. The adsorption spectrum shows that TMTZ crystal has higher absorption coefficients in the wavelength range from 180nm to 325nm, which indicates that the UV cut-off wavelength occurs at 325 nm. At last the hyperpolarizability of TMTZ single crystal was calculated, and the nonlinear optical properties of ZMTC crystal has an obvious increase as adding SCN2H4 ligand .

Theory investigation on structure and optical properties of TMTZ single crystal

254th National Meeting (2017)

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