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Abstract: The model for amorphous semiconductor InSb (a-InSb) was constructed through the first principles calculations, based on the idea of “continuous random networks” (CRN). The results of structural parameters for a-InSb are in agreement with the available data both theoretically and experimentally. The structure of a-InSb is almost tetrahedrally bonded with a perfect average coordination number of four. Due to the influence of the disorders, the density of states for a-InSb has the smearing structure in contrast to crystalline InSb (c-InSb). As a consequence of the induction of disorders, modification phenomena occur at the band edge of a-InSb in contrast to that of c-InSb. [Copyright &y& Elsevier]

Abstract: First-principles calculations have been performed on the C-doped anatase TiO2. The doped TiO2 shows half-metallic properties and a 2.0 μB magnetic moment per cell. The magnetic coupling is closely related to the C–C distance. When the distance is shorter than a typical CC double bond (), the system is nonmagnetic and the dopants tend to form a cluster through a direct CC bonding interaction [Appl. Phys. Lett. 93 (2008) 132507]. When the distance is between 3.8 and , there exists strong ferromagnetic or antiferromagnetic coupling between two C atoms. The ferromagnetic coupling is induced by the bent C–Ti–C unit. When the distance is further increased, the system becomes paramagnetic. [Copyright &y& Elsevier]

Abstract: Ball mill grinding circuits are essentially multi-variable systems characterized with couplings, time-varying parameters and time delays. The control schemes in previous literatures, including detuned multi-loop PID control, model predictive control (MPC), robust control, adaptive control, and so on, demonstrate limited abilities in control ball mill grinding process in the presence of strong disturbances. The reason is that they do not handle the disturbances directly by controller design. To this end, a disturbance observer based multi-variable control (DOMC) scheme is developed to control a two-input-two-output ball mill grinding circuit. The systems considered here are with lumped disturbances which include external disturbances, such as the variations of ore hardness and feed particle size, and internal disturbances, such as model mismatches and coupling effects. The proposed control scheme consists of two compound controllers, one for the loop of product particle size and the other for the loop of circulating load. Each controller includes a PI feedback part and a feed-forward compensation part for the disturbances by using a disturbance observer (DOB). A rigorous analysis is also given to show the reason why the DOB can effectively suppress the disturbances. Performance of the proposed scheme is compared with those of the MPC and multi-loop PI schemes in the cases of model mismatches and strong external disturbances, respectively. The simulation results demonstrate that the proposed method has a better disturbance rejection property than those of the MPC and PI methods in controlling ball mill grinding circuits. [Copyright &y& Elsevier]

Abstract: The electronic structure in p-type δ-doping GaAs is calculated self-consistently by including the contribution of the photogenerated carrier. The theoretical results indicate that the band bending around the δ-doping region is induced by the injection of photogenerated holes into the potential well of the δ-doping GaAs. Moreover the band bending results in two photogenerated carrier-induced wells for electrons. The potential of the two wells is deepened with the increase of the photogenerated carrier density. The photoluminescence (PL) properties are explained in terms of the dependence of the confined electronic states and the Fermi level of the two-dimensional hole gas (2DHG) on the concentration of photogenerated carrier, which is in good agreement with experimental observation of the variation of peak position and intensity with the excitation light intensity. [Copyright &y& Elsevier]

Abstract: There is a significant diminution in the hydrostatic pressure coefficients (PCs) of the photoluminescence spectrum for InAs/GaAs quantum dots in comparison with that of bulk binary. We study this phenomenon with the nonlinear elasticity theory. The variation of the lattice and elastic constants plays an important role in the change of PCs, which causes the obvious decrease of the built-in strains of InAs/GaAs quantum dots under the hydrostatic pressure. The decrease will induce the novel change of the energy gap and the electronic confined energy. Finally, the change is shown in the measured small PCs of photoluminescence from quantum dots. Also the calculation reveals that the PCs are sensitive to the sizes of quantum dots because of the change of the electronic confined energy. The smaller the quantum dot is, the stronger the influence of this change on the PCs becomes. This effect gives rise to the increase of PCs when dot size is reduced. [Copyright &y& Elsevier]

The effect of Nb doping of oxide perovskite SrTiO3 on the electronic properties is studied by semirelativistic linear muffin-tin orbital method with atomic sphere approximation (LMTO-ASA). The computational lattice constants are in good agreement with experimental data. The Fermi level of SrTi1−xNbxO3 with x⩾0.125 moves into the bottom of conduction band and the system shows metallic behavior. Due to the appearance of the charge impurity potential from Nb doping, there is a large distortion on the top of valence band for SrTi1−xNbxO3 with 0.125⩽x⩽0.25. The distortion becomes weak with x=0.5 because of the carriers screening effect. Our computational results also show that the Nb doping effect on the electronic structure of SrTi1−xNbxO3 cannot be described within a simple rigid-band model well. [Copyright &y& Elsevier]

The electronic and optical properties of Nb doped SrTiO3 are studied by ab initio linear muffin-tin orbital method in the atomic sphere approximation. The equilibrium lattice constants of SrTi1−xNbxO3 with x=0.0, 0.25 and 0.5 are found by minimization of the total energy curves. The computated lattice constants are in good agreement with experimental data. Our electronic band calculation shows that the Fermi level of SrTi1−xNbxO3 with x≥0.125 moves into the conduction bands and the system shows metallic behavior. The numerical results indicate that the Nb impurity atoms would lead to the distortion of the band edges. The complex dielectric function of SrTiO3 and Nb doped SrTiO3 are calculated using the random-phase approximation. The doping effect on the optical properties of SrTi1−xNbxO3 is discussed. [Copyright &y& Elsevier]

Highlights: [•] Al2O3/HfO2/Al2O3 gate stacks has been deposited on Si substrate by ALD. [•] Interface thermal stability related with annealing temperature has been studied. [•] Phase separation at 700°C and silicate formation at 900°C have been detected. [ABSTRACT FROM AUTHOR]

Abstract: Graphene is a basic building block for carbon materials of all dimensionalities and exhibits many unique electronic properties. But, for future applications of graphene, further tuning its electronic band structure is necessary. Recently, it has been demonstrated that graphene can react with atomic hydrogen, which transforms this zero-band-gap semimetal into an insulator [[17] Elias et al., Science 323 (2009) 610]. Here we investigate the electronic and vibrational properties of graphene sheets with H in various configurations by means of first-principles calculations based on density-function theory. It is found that the hydrogenation not only effectively modulates the band gap of graphene but also leads to the band gap transition from direct to indirect. Meanwhile, the emerging of the sp3 type bonds induced by the hydrogenation may introduce some new vibrational modes in graphene, which play a key role in determining the spectra signatures of the resulting graphene derivatives. Our results provide a satisfactory explanation for the experimentally observed changes of the Raman spectra in graphene during the hydrogenation. [Copyright &y& Elsevier]

Abstract: By use of first-principles calculations, we examine the effects of uniaxial strain on the electronic and magnetic properties of Co-doped ZnO nanowires. Our results show that the uniaxial strain can cause significant variation of magnetic interactions in different ways, which are strongly dependant on the configuration formed by Co atoms. For the configuration whose ground state is a ferromagnetic state, the uniaxial tensile strain leads to the enhancement of ferromagnetic interaction, which can be explained by the double-exchange model very well. It is also shown that the strength of the double-exchange interaction is dependent on the occupation of the Co-3 state. The present results indicate the strain can be used as an effective means in tuning the magnetic interactions in ZnO based one-dimensional diluted magnetic semiconductors. [Copyright &y& Elsevier]

Abstract: Using first-principles method we studied the compensation mechanism of As donor in Hg1− x Cd x Te based on the model Berding et al. (1998, 1999) of pair. We show that the binding of AsHg and results from donor-acceptor coupling, and the compensation of As donor can be clearly explained in terms of electronic deactivation by . The pairing physics derived from this study confirm the available theoretical and experimental results. [ABSTRACT FROM AUTHOR]