Nanocomposites and nanomaterials

Structural and electronic properties of ZnO nanoporous phases: an ab initio study 
Dzikovskyi V.Ye., Bovgyra O.V., Kovalenko M.V., Vasil’yev V.S.
Faculty of Physics, Ivan Franko National University of Lviv, 8a, Kyrylo and Mefodiy str., 79005 Lviv, Ukraine. 
E-mail: mariya.kovalenko@lnu.edu.ua

Zinc oxide (ZnO) is a group II−VI semiconductors and is well known for its excellent performance in various application domains such as piezoelectrics, pyroelectrics, optoelectronics, and spintronics. Since the discovery of the excellent properties and applications of aluminosilicate zeolites in the areas of ion-exchange, separations, and catalysis, the sector of inorganic open-framework materials has become one of the intense research interests. Additionally in the current search for new and interesting nanoporous open-frameworks, the prediction of their framework design and dimensionality are too important. Besides the extensive experiments to find new phases, theoretically, the crystal structure predictions from first principles have also been widely reported [1, 2].
In this work, based on the bottom-up approach, which provides a reliable way to build new structures from free clusters to cluster-assembled solid phases, we present the results of the first-principles modeling of zeolite structures of ZnO (SOD, LTA, FAU, CAN, LOS, FRA, KFI, RHO, TSC). Structure optimization and band energy calculations were performed within the density functional theory (DFT), using the generalized gradient approximation (GGA) in the PBE parameterization. We used the GGA+U approximation for more accurately describe the electronic structure of nanoporous ZnO.
The calculations results of the electronic structure show that all nanoporous structures are wide bandgap semiconductors with a bandgap bigger wurtzite and zinc-blend phase, respectively, from 21% up to 56% larger than that of wurtzite ZnO. Certainly, it leads to higher flexibility and compressibility (lower bulk moduli) of the new hollow phases. Therefore, these new nanoporous phases if they are could be synthesized will be one of the most promising candidates for replacing the expensive and mechanically fragile atomic or molecular selective materials.

1.	Woodley S. M., Catlow R. Crystal structure prediction from first principles // Nat. Mater. -2008.-7.-P. 937−946.
2.	Tuoc V. N., Liên L., Huan T. D., N. Thao Novel cage-like nanoporous ZnO polymorphs with cubic lattice frameworks // Materials Today Communications. -2020.- 24.- P. 101152 (7 p.).