Program

O.21 -- Oral, NCTP-41

Date: Wednesday, 3 August 2016

Time: 14h40 - 15h00

Theoretical prediction of ZnO hollow framework nanoporous structures

Vu Ngoc Tuoc (1), Tran Doan Huan (2), Nguyen Thi Thao (1, 3)

(1) Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Rd., Hanoi 100000, Vietnam (2) Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136, USA (3) Hong Duc University, 307 Le Lai, Thanh Hoa city, Vietnam

Along with wurtzite and zinblende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties, and hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs is of great significance and has been gaining considerable interest. Herein, we perform a density functional theory based study, predicting several new series of ZnO flexible hollow structures using the bottom-up design approach. For the structural phase stability, our calculations show that these hollow structures could survive in periodic systems without structural collapse, which leads to nanoporous low-density phases of ZnO. We found that the bulk modulus have saturated at certain hollow's wall thickness regarding to hollow-to-bulk density ratio. Consequently, for the purpose of low-density geometry engineering, the optimal value for strength-to-density figure of merit should reach a certain critical thickness. Their room temperature stability is discussed by means of the free energy computed within the lattice-dynamics approach. Our calculations also indicate that all the reported nanoporous structures, if synthesized, would preserve the valuable properties of the ZnO materials, e.g. wide bandgap semiconducting, piezoelectric and optically transparent, while, at the same time, would possess novel properties as of band flattening and gap engineering possibility. The electronic band structures of the ZnO hollow structures are finally examined in details.

Presenter: Vu Ngoc Tuoc