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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]

MoS2-WS2 thin layers with different deposition sequences and stacking configurations have been studied using first principles full potential linearized augmented plane wave method. The electronic and optical properties of ten atomic layers (in [0 0 0 1] direction) of MoS2-WS2 are reported in the present paper. Ten layers of MoS2-WS2, which are free from quantum size effects, show an indirect band gap which varies between 0.89 and 1.22 eV by engineering of the layering sequence and stacking configuration. Optical properties like absorption coefficients, dielectric tensors and refractive indices of bilayer and multilayer films of MoS2-WS2 are determined and are found to be different from the ten layers of MoS2 and WS2. Changes in the electronic and optical properties of multilayers have been elaborated in terms of interlayer and intralayer S-S distances. A comparison of absorption spectra deduced using the first principles calculations for Si and different combinations of multilayers of MoS2-WS2 show their applicability in optoelectronics and photovoltaic devices. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have investigated the electronic, optical and mechanical properties of the Y2O3 crystal by first-principle calculations based on the density–functional theory. The generalized gradient approximation (GGA-PBE) and hybrid exchange–correlation functional (HSE06) are both used for comparative study. It is found that, the band gap of Y2O3 calculated by HSE06 method (6.0eV) is in good agreement with the experimental band gap data (5.5eV), and HSE06 gives better electronic structure description close to experiments. Then we calculate the elastic constants, and derive the corresponding properties i.e.; bulk, shear and Young’s moduli, and Poisson’s ratio. Our calculated elastic and mechanical properties correspond well with experimental data. Besides, we also obtain the equilibrium lattice and bulk modulus of yttria by fitting the Birch–Murnaghan equation of state. It is found that, the HSE06 well reproduce the experimental lattice parameters, equilibrium volume and bulk modulus of Y2O3. Based on the accurate described crystal and electronic structure and mechanical properties by HSE06 method, the optical properties of this material are also analyzed. [Copyright &y& Elsevier]