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

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).