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Graphical abstract Highlights • Structural, magnetic and optical properties of Mg-doped CeO 2 (1 1 1) surface were investigated. • The doped CeO 2 (1 1 1) surface systems exhibit different bonding character. • The doped surface and subsurface systems result in local and scattered spin atmosphere. • The incorporation of Mg can lead to the red shift of absorption edge. Abstract The electronic structure, magnetic and optical properties of Mg-doped CeO 2 (1 1 1) surface have been investigated by first-principles calculations. In this paper, the doping case is actively favorable to process under O-rich conditions than under Ce-rich conditions. The distortion of doping systems of Mg replacing Ce of surface is larger than that of subsurface. The covalent character is getting weaker and the ionic character is gradually obvious for Mg O bond from surface to subsurface doping. The results show that the existence of defect states with O 2 p orbital character makes spin splitting, causing the local and scattered magnetic moments for surface and subsurface doping of Ce, respectively. And the 9 and 12 atomic layers doping systems exhibit magnetic ground states with different magnetic moments. In particular, the calculated Curie temperature (about 434, 483, 1200 K) is higher than room temperature (RT), therefore, the theoretical results showed that Mg-doped CeO 2 (1 1 1) thin films would can be obtained stable room temperature ferromagnetism (RTFM), which is beneficial to practical application. In addition, the optical properties show that all doped systems are capable of enhancing effective absorption of visible and near-infrared light. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) is a new two-dimensional (2D) material. It has received significant attention because of its great potential in the field of optoelectronics, which arises due to its low-dimensional effects. In this paper, the effect of bi-axial strain on the band structure of monolayer BP has been studied by using the first-principles method based on density functional theory (DFT). We find that the band gap range of monolayer BP can be moderately and effectively adjusted by external stress from 0 to 1.845 eV. Simultaneously, the direct band gap is maintained during the stretching process, which leads to a high electron mobility suitable for applications. Moreover, the compressive strain can result in a semiconductor–metal transition (SMT) with few-layer BP, whereas tensile strain only affects the band gap. Based on the electronic properties of monolayer BP, its optical properties are analyzed in detail, and the influence of strain—from a compressive strain of 12% to a tensile strain of 12%—on these properties is systematically discussed. It is found that the strain range and mode have a significant impact on the optical properties. In addition, the dielectric function and absorption spectra calculated along two different directions indicate that a significant optical anisotropy appears, giving a strong directionality dependence in the primitive and strained monolayer BP. It can be concluded that by applying external stress to monolayer BP, its optical properties can be readily controlled, which is beneficial for device applications. Furthermore, based on its direction-dependent response to the external stress, this behavior can also be used to detect the orientation of the deposited BP without the need for precise electron microscopy. [ABSTRACT FROM AUTHOR]