Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence

Abstract

The electronic structure of Zn(OH)₂ has been studied by first-principles calculations using the local density approximation + Hubbard U (LDA+U) scheme. Based on the LDA+U calculations of ZnO and Zn(OH)₂, a principle for the correct assignment of the U values has been established. The assigned U values should assure an appropriate overlap of the Zn 3d and O 2p states. Both theoretical calculations and experimental investigations have determined an energy band gap of 5.65 eV for Zn(OH)₂. We also report abnormal yellow luminescence of Zn(OH)₂ resembling that of ZnO. Characterizations of cathodoluminescence, UV-Vis absorption and X-ray photoelectron spectroscopy reveal that ZnO of several atomic layers in thickness covers the surface of Zn(OH)₂, which gives rise to the intense yellow luminescence observed for Zn(OH)₂.