Electronic and optical properties of zinc based hybrid organic-inorganic compounds

Abstract

There is significant interest in hybrid organic-inorganic (HOI) compounds since these materials offer multiple functionalities and properties that can be tailored at the mesoscopic and nanoscale levels. HOIs investigated for photovoltaic applications typically contain lead or mercury. There is considerably less work done on Zn-based HOIs. These could potentially be considered in biomedical applications due to presence of organic components and the biocompatibility of Zn cations. Using a systematic materials selection approach, we have carried out a detailed search of Zn-HOI compounds in two comprehensive experimental crystallographic repositories: Inorganic Crystal Structure Database and American Mineralogist Crystal Structure Database. Thirteen Zn-HOI compounds are discovered: CuZnO 2 (CO 3 ), Zn(C 2 O 4 ), ((CH 3 ) 2 NH 2 )Zn 3 (PO 4 )(HPO 4 ) 2 , (CH 3 NH 3 )Zn 4 (PO 4 ) 3 , Zn(N(CH 2 PO 3 H) 3 )(H 2 O) 3 , (CH 3 NH 3 )Zn(HCO 2 ) 3 , Zn 4 (CO 3 ) 2 , Zn 8 (HPO 4 ) 16 (C 2 H 8 N) 8 , Zn 5 (CO 3 ) 2 , (Mg 2 Zn) 8 (CO 3 ) 2 (OH), Zn 7 (CO 3 ) 2 (OH) 10 , Ca 3 Zn 2 (PO 4 )CO 3 (OH).2H 2 O, and Zn(CO 3 ). We have then performed first principles calculations via density functional theory with hybrid functional treatment to determine the electronic band gap and optical response of these materials. Our computations show that eleven of the thirteen compounds have insulating properties with band gaps ranging from 2.8 eV to 6.9 eV. Ten of these are found to have a high absorbance in the far ultra-violet (FUV) region of 200-112 nm wavelength. For example, the absorption coefficient of (CH 3 NH 3 )Zn(HCO 2 ) 3 is ∼0.75×10 5 cm −1 for F 2 excimer laser energy (wavelength ∼157 nm) which is more than three orders higher than the average tissue absorbance (∼10 1.5 cm −1 ) and the refractive index of 1.85 is larger than typical biological matter which is in the range 1.36-1.49. These results suggest that Zn-HOIs could potentially find applications in photothermolysis and UV protection.

Data-driven methods for discovery of next-generation electrostrictive materials

“…To assign proxies for selecting materials exhibiting high electrostriction, we utilize a set of relationships between the dielectric response, the elastic coefficients, the electric field-induced strain, and the electrostrictive properties of materials as described in the previous section. A similar methodology developed by Newnham Existing databases of calculated functional properties provide easy access to data that can be used to shortlist materials with exceptional properties via a simple database query of related proxies 26,27 . The Materials Project (MP) serves as an ideal platform for novel materials discovery, given the large number of calculated material properties and optimized crystal structures contained in the database 28 .…”