Synthesis, Characterization, Nucleation Kinetics, Mechanical, Photo Conductivity, Birefringence and DFT Studies of Tris(thiourea) Zinc Selenate as Potential NLO Material

Abstract

Semi-organic single crystals of pure tris(thiourea) zinc selenate (TTZS) were grown from aqueous solution by slow evaporation method. Nucleation kinetics of grown TTZS was extensively studied through which important nucleation parameters were calculated. Further, the fair agreement between the experimental and theoretical interfacial energy values was successfully established. X-ray diffraction studies revealed the orthorhombic nature and Pca21 space group of the title crystal. Theoretically calculated bond lengths and bond angles were found to be in accordance with that of experimental XRD values but with minor deviations. The sharp peak in the HRXRD pattern indicated the higher degree of crystallinity of the sample. The micro hardness analysis was carried out to ascertain the mechanical strength of the TTZS crystal. The mechanical studies also helped to deduce Meyer’s index, elastic modulus, yield strength, fracture toughness, elastic stiffness coefficient and brittleness index. Kurtz-Perry powder technique suggested the phase matching nature of TTZS crystal and it further indicated that the SHG efficiency of TTZS is 1.12 times as that of standard KDP. The photoconductivity analysis resulted in the higher magnitude of dark currents than the photo current which suggested the negative photo conductivity nature of the TTZS crystal. The sample showed low value of birefringence (0.0483 at 532 nm). The laser damage threshold value of TTZS was found to be 2.60 GW/cm2. The charge distribution of Mulliken atomic charges, non-linear optical (NLO) and natural bond orbital (NBO) analyses were calculated by ab-initio method. The Frontier orbital analysis was employed to arrive at the values of global chemical molecular reactivity descriptors.