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Along the lines indicated by recent papers, I have revised my results for the absorption and dispersion properties of the pyramid shaped quantum dots under the simultaneous action of incident light and external electric field. The results related to: (i) electronic structure calculations in pyramid shaped quantum dots under applied electric fields and (ii) the tuning of the optical absorption and the group velocity by varying the electric field strength and the ellipticity parameter of the probe light pulse remain unaffected. However, great dissimilarities are found between the old and new results for large intensities of the incident light. [ABSTRACT FROM AUTHOR]

In this paper, Fe-N 3 S 1 and FeS sub-nano cluster are innovatively connected to S, N co-doped carbon matrix (SNC) by controlled calcination process. The local electron configuration of Fe center is modulated by this unique structure. Based on this design, Fe-N 3 S 1 and FeS sub-nano cluster shown excellent synergistic effects in oxygen reduction reaction. The optimized ORR activity was obtained. [Display omitted] Single atomic Fe-N 4 catalyst exhibits a great prospect for oxygen reduction reaction (ORR) and adjusting the intrinsic coordination structure and the carbon matrix structure effectively improves the catalytic activity. However, controlling the active site coordination structure and its surrounding environment at atomic level remains a challenge. In this paper, Fe-N 3 S 1 and FeS sub-nano cluster were innovatively concatenated on S, N co-doped carbon matrix (SNC), denoted as FeS/FeSA@SNC catalysts, for modulating ORR catalysis performance. Both experimental measurements and theoretical calculations have confirmed that the local electron configuration of Fe center is modulated by this unique structure combination leading to optimized ORR kinetics. Based on this design, the synthesized FeS/FeSA@SNC delivers ORR activity with a half-wave potential of 0.9 V (vs. RHE), excelling that of commercial Pt/C (0.87 V) and the Zn-air battery (ZAB) with this cathode catalyst delivers a peak power density of 126 mW cm−2. This work presents a novel strategy for manipulating the single-atom active sites through control the local coordination structure and provides a reference for the development of novel efficient ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

This work vividly demonstrates the rational design of VSe 2-x O x -SS cathode as an effective strategy to achieve fast and highly aqueous zinc ion storage. [Display omitted] • A simple and fast surface oxygen implantation strategy was designed to adjust the electronic structure of VSe 2 and form a surface protective film. • The VSe 2-x O x -SS-30 electrode showed higher specific capacity, better rate performance and more satisfactory cycling stability. • The zinc (de)intercalation and transformation reactions mechanism was revealed by some ex-situ/in-situ techniques. Interfacial chemical modification is an effective strategy to adjust the strong Coulombic ion-lattice interactions with high valence cations experienced by electrode materials, facilitating the reaction kinetic. In this paper, a simple and fast surface oxygen implantation strategy was designed to adjust the electronic structure of stainless steel (SS) supported vanadium diselenide (VSe 2) nanosheets and form a surface protective film, which effectively accelerates the reaction kinetics of Zn2+ and extends the cycle life of the battery. It is demonstrated that the conductivity, pseudocapacitance and specific capacity can be tuned by selectively introducing oxygen species to the surface, which provides an important reference for the design of electrodes with controlled surface chemistry. Density functional theory (DFT) calculations also confirm that the electronic structure can be adjusted by surface oxygen injection strategy, which not only improves the conductivity, but also adjusts the adsorption energy, thus providing favorable conditions for zinc ion storage. Benefiting from the selenium vacancies and pores generated by the removal of part of selenium, and the oxide film formed on the surfaces, the VSe 2-x O x -SS-30 electrode showed higher specific capacity (188.4 mAh/g at 0.5 A g−1 after 50 cycles), better rate performance (107.1 mAh/g at 4 A g−1) and more satisfactory cycling stability (83.1 mAh/g at 5 A g−1 after 1800 cycles) than VSe 2 -SS electrode. Importantly, the flexible quasi-solid-state VSe 2-x O x -SS-30//Zn battery also exhibits high specific capacity and excellent environmental adaptability. Furthermore, the zinc (de)intercalation and transformation reactions mechanism was revealed by some ex-situ/in-situ techniques. [ABSTRACT FROM AUTHOR]

Facile synthesis of FeNi alloy-supported N -doped Mo 2 C hollow nanospheres for enhanced oxygen evolution reaction. [Display omitted] • Facile synthesis of FeNi alloy-supported N -doped Mo 2 C hollow nanospheres. • FeNi/Mo 2 C/NC supports strongly accelerated electron transfer, thereby improving the OER kinetics. • FeNi/Mo 2 C/NC hybrids will hold promise in development of electrode materials. The rapid depletion of fossil fuels results in significant environmental pollution. Consequently, researching environmentally friendly and cost-effective electrocatalysts with exceptional oxygen evolution reaction (OER) capabilities holds immense importance in enhancing the efficient utilization of resources. In this paper, a straightforward and cost-effective method was employed to produce Fe-Ni alloy-supported N -doped carbon hollow nanospheres (FeNi/Mo 2 C/NC) using self-assembled molybdenum dopamine spheres (Mo-PDA-HS) as a substrate. The inclusion of iron and nickel addressed the issue of aggregation and collapse in Mo-PDA-HS nanostructures at high temperatures, while adjusting the electronic structure of the composites to achieve efficient OER activity. The composite displayed a low overpotential (η10 mA = 304 mV) and a minimal Tafel slope (41.8 mV/dec-1). This study introduces a simple strategy for constructing structurally robust and non-aggregating Mo 2 C nanostructures, along with a direct method for designing cost-effective and high-performance catalysts for OER. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar energy conversion into hydrogen (H 2) energy has attracted much attention. However, the low light utilization rate and fast carrier recombination of photocatalysts extremely limit the practical application of photocatalytic H 2 production. In this paper, MoSe 2 -NiSe with abundant active sites and interfacial electronic structures as dual co-catalysts were assembled on g-C 3 N 4 nanosheets (NSs) vis a solvothermal reaction process. MoSe 2 -NiSe/g-C 3 N 4 NSs composite exhibited improved light absorption and photoelectrochemical properties. The photocatalytic H 2 production rate of MoSe 2 -NiSe/g-C 3 N 4 composite achieved 2379.04 μmol·h−1·g−1, which is 99.25, 1.44, and 3.67 times those of pure g-C 3 N 4 nanosheets (23.97 μmol·h−1·g−1), MoSe 2 /C 3 N 4 (1654.57 μmol·h−1·g−1), and NiSe/C 3 N 4 (649.08 μmol·h−1·g−1), respectively. The apparent quantum efficiency (AQE) value of MoSe 2 -NiSe/g-C 3 N 4 achieved 4.07 % under light at λ = 370 nm. The corresponding characterization and experiments proved that 2D ultrathin g-C 3 N 4 NSs with a large surface area and short charge-transfer distance could facilitate light scattering and the transport of photoexcited electrons. MoSe 2 -NiSe, as a dual co-catalyst, showed strong electronic synergistic interaction between the interfaces, thus improving the conductivity and promoting the electron transfer process. [ABSTRACT FROM AUTHOR]

We propose an unconditionally energy-stable, orthonormality-preserving, component-wise splitting iterative scheme for the Kohn-Sham gradient flow based model in the electronic structure calculation. We first study the scheme discretized in time but still continuous in space. The component-wise splitting iterative scheme changes one wave function at a time, similar to the Gauss-Seidel iteration for solving a linear equation system. At the time step n , the orthogonality of the wave function being updated to other wave functions is preserved by projecting the gradient of the Kohn-Sham energy onto the subspace orthogonal to all other wave functions known at the current time, while the normalization of this wave function is preserved by projecting the gradient of the Kohn-Sham energy onto the subspace orthogonal to this wave function at t n + 1 / 2. The unconditional energy stability is nontrivial, and it comes from a subtle treatment of the two-electron integral as well as a consistent treatment of the two projections. Rigorous mathematical derivations are presented to show our proposed scheme indeed satisfies the desired properties. We then study the fully-discretized scheme, where the space is further approximated by a conforming finite element subspace. For the fully-discretized scheme, not only the preservation of orthogonality and normalization (together we called orthonormalization) can be quickly shown using the same idea as for the semi-discretized scheme, but also the highlight property of the scheme, i.e., the unconditional energy stability can be rigorously proven. The scheme allows us to use large time step sizes and deal with small systems involving only a single wave function during each iteration step. Several numerical experiments are performed to verify the theoretical analysis, where the number of iterations is indeed greatly reduced as compared to similar examples solved by the Kohn-Sham gradient flow based model in the literature. • This paper proposes a novel and efficient numerical scheme for the Kohn-Sham gradient flow based model. • The scheme is an unconditionally energy-stable, orthonormality-preserving, component-wise splitting iterative scheme. • The scheme does not modify the original energy, allows large time step sizes, and solves small systems at each time step. • The rigorous proof is presented in the paper. • Several numerical examples are illustrated to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The porous few-layer bimetallic co-doped g-C 3 N 4 is prepared via a facile bottom-up method. • The bimetallic synergetic regulating effect on the electronic structure can be produced in Co/Ni-g-C 3 N 4. • The superior performance results from the improved charge separation efficiency and visible light harvestability. • This work provides meritorious guidance for new bimetallic co-doped g-C 3 N 4 photocatalysts. The low specific surface area and low charge transfer efficiency of conventional graphite carbon nitride (g-C 3 N 4) are the main obstacles to its application in photocatalytic CO 2 reduction. In this paper, graphite carbon nitride was protonated by phosphoric acid (H 3 PO 4), and a new few-layer porous carbon nitride was prepared by intercalation polymerization with doping bimetal in the cavity of g-C 3 N 4. Under visible light irradiation, the CO formation rate of Co/Ni co-doped g-C 3 N 4 can reach 13.55 μmol g−1 h−1, which was 3.9 times higher than that of g-C 3 N 4 (3.49 μmol g−1 h−1). The density functional theory (DFT) calculations showed that the addition of Co and Ni in the cavity of g-C 3 N 4 can induce bimetallic synergistic regulation of the electronic structure, thus improving the separation efficiency of charges and visible light capture ability of g-C 3 N 4. Our work has great reference value for designing and synthesizing novel bimetallic co-doped g-C 3 N 4 photocatalytic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] As a promising dopant, electron deficient B atom not only tunes the electronic structure of electrocatalysts for improving their intrinsic catalytic activities, but also combines with hydroxy radical as strong adsorption sites for accelerating the water dissociation during the hydrogen evolution reaction (HER). In this paper, we report an electrocatalyst based on boron-modified Ru anchored on carbon nanotubes (B-Ru@CNT) that shows impressive HER activity in acidic and alkaline media. The boron-rich closo -[B 12 H 12 ]2- borane was selected as a moderately strong reductant for the in situ reduction of a Ru salt, which yielded B-doped Ru nanoparticles. The experimental and theoretical results indicate that the incorporation of B not only weakens the Ru-H bond and downshifts the d-bond centre of Ru from the Fermi level by reducing the electron density at Ru but also accelerates the water dissociation reaction by providing B sites, which strongly adsorb OH* intermediates, and nearby Ru sites, which act as sites for the adsorption of the H* intermediate, thus boosting the HER performance and enhancing the HER kinetics. As a result of the tuning of the electronic structure via B doping, B-Ru@CNT showed excellent HER performance, yielding overpotentials of 17 and 62 mV at a current density of 10 mA cm−2 in alkaline and acidic solutions, respectively. These results indicate that our synthetic method is a promising route to B-doped metallic Ru with enhanced pH-independent HER performance. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the correlation between setback and high-impact test loadings using the shock response spectrum (SRS). The modal analysis of the electronic assembly structure is implemented to determine the frequency range for the SRS analysis. A preliminary test of the high-impact tester is conducted with a reference impact velocity. Based on experimental data, finite element (FE) simulation is employed to predict the acceleration states at different impact velocities. The acceleration curves generated from FE simulation are included in the shock response spectrum for the correlation analysis. A proposed impact velocity is expected to cause a similar damage to the electronic assembly structure. This study provides valuable insight into the relationship between setback and high-impact test loadings, as well as a method for predicting and evaluating the potential damage to electronic assembly structures during high-impact testing. [ABSTRACT FROM AUTHOR]

The Anderson acceleration method is an algorithm for accelerating the convergence of fixed-point iterations, including the Picard method. Anderson acceleration was first proposed in 1965 and, for some years, has been used successfully to accelerate the convergence of self-consistent field iterations in electronic-structure computations. Recently, the method has attracted growing attention in other application areas and among numerical analysts. Compared with a Newton-like method, an advantage of Anderson acceleration is that there is no need to form the Jacobian matrix. Thus the method is easy to implement. In this paper, an Anderson-accelerated Picard method is employed to solve the three-temperature energy equations, which are a type of strong nonlinear radiation-diffusion equations. Two strategies are used to improve the robustness of the Anderson acceleration method. One strategy is to adjust the iterates when necessary to satisfy the physical constraint. Another strategy is to monitor and, if necessary, reduce the matrix condition number of the least-squares problem in the Anderson-acceleration implementation so that numerical stability can be guaranteed. Numerical results show that the Anderson-accelerated Picard method can solve the three-temperature energy equations efficiently. Compared with the Picard method without acceleration, Anderson acceleration can reduce the number of iterations by at least half. A comparison between a Jacobian-free Newton–Krylov method, the Picard method, and the Anderson-accelerated Picard method is conducted in this paper. [ABSTRACT FROM AUTHOR]

[Display omitted] Defect engineering is an important strategy to regulate electronic structure of electrocatalysts for electrochemical N 2 fixation, aiming at improving the electron state density and enhancing the adsorption and activation of inert N 2. In this paper, a high-temperature strategy to anneal the natural molybdenite under Ar atmosphere was developed, and the as-obtained molybdenite with S vacancies boosted a high activity for N 2 reduction reaction. In 0.1 M HCl, the catalyst annealed at 800 °C exhibits a high Faradic efficiency of 17.9% and a NH 3 yield of 23.38 μg h−1 mg-1 cat. at −0.35 V versus reversible hydrogen electrode, two times higher than that of the pristine molybdenite. The facile one-step annealing method introduces the defects (e.g., S vacancies) in the surface of the natural molybdenite particles to prepare catalysts for generating ammonia by reducing nitrogen at room temperature under ordinary pressure, promoting the development of low-carbon economic prospect. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) graphitic carbon nitride (g-C 3 N 4) nanoplates (CNNP) have become a hot research topic in photocatalysis due to their small thickness and large specific surface area that favors charge transport and catalytic surface reactions. However, the wide application of 2D g-C 3 N 4 nanoplates prepared by ordinary methods suffers from increased band gaps with a poor solar harvesting capability caused by the strong quantum confinement effect and reduced conjugation distance. In this paper, a facile approach of exfoliation and the following fast thermal treatment of the bulk g-C 3 N 4 is proposed to obtain a porous few-layered g-C 3 N 4 with nitrogen defects. Due to the preferable crystal, textural, optical and electronic structures, the as-obtained porous CNNP demonstrated a significantly improved photocatalytic activity towards water splitting than the bulk g-C 3 N 4 and even the 3 nm-thick CNNP obtained by sugar-assisted exfoliation of the bulk g-C 3 N 4. The difference in the enhancement factors between the H 2 O splitting and organic decomposition has revealed the effect of N defects. This study offers insightful outlooks on the scalable fabrication of a porous few-layered structure with a promoted photocatalytic performance. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we construct an efficient numerical scheme for full-potential electronic structure calculations of periodic systems. In this scheme, the computational domain is decomposed into a set of atomic spheres and an interstitial region, and different basis functions are used in different regions: radial basis functions times spherical harmonics in the atomic spheres and plane waves in the interstitial region. These parts are then patched together by discontinuous Galerkin (DG) method. Our scheme has the same philosophy as the widely used (L)APW methods in materials science, but possesses systematically spectral convergence rate. We provide a rigorous a priori error analysis of the DG approximations for the linear eigenvalue problems, and present some numerical simulations in electronic structure calculations. [ABSTRACT FROM AUTHOR]

Abstract In this paper, four types of compounds are considered: ideal wurtzite (B N), N vacancies in B N (B N − V N), A l doped ideal B N (A l : B N) and A l doped B N with N vacancies(A l : B N − V N). The structural, electronic and magnetic properties are calculated by using the density functional theory (DFT) based on the generalized gradient approximation implemented in Quantum-Espresso code. Our results show that the nitrogen vacancies and the aliminium impurities are responsible of the magnetic properties in these compounds. We have also found that aluminium impurities have a remarkable effect on the optical band gap. Our results are in good agreement with experimental and other theoretical studies. We can conclude from this study, that this material can be used as diluted magnetic semiconductors. Highlights • The DFT method has been used to study the Al doped (w−BN). • The lattice parameters increase with the incorporation of Al in the BN supercell. • The Al impurities decrease the value of the band gap. • Al and N vacancy induce magnetic properties. [ABSTRACT FROM AUTHOR]

Abstract For the first time, a mixed-alkali diphosphate, Li 2 Na 2 P 2 O 7 , has been successfully obtained by high-temperature solution growth (HTSG) method. Single crystal X-ray diffraction analysis reveals that it contains anionic [Li 2 P 2 O 7 ] ∞ network and 1D [Na] ∞ infinite chains, which are both running along the c -axis. Band structure calculations by density functional theory (DFT) method indicate that Li 2 Na 2 P 2 O 7 has an indirect band gap of about 4.88 eV. Moreover, 1 mol% Eu3+ doped Li 2 Na 2 P 2 O 7 phosphor was synthesized and its photoluminescence properties were investigated. Under near ultraviolet (NUV) excitation (394 nm), Li 2 Na 2 P 2 O 7 :0.01Eu3+ phosphor exhibits a series of emission peaks corresponding to the 5D 0 →7F J (J = 0, 1, 2, 3, 4) transitions of Eu3+ ion with the CIE chromaticity coordinates of (0.599, 0.375). Graphical abstract This paper affords a novel lithium sodium diphosphate Li 2 Na 2 P 2 O 7 via high temperature flux method. The wide band gap of about 4.88 eV makes it suitable to be used as a luminescent host matrix. It can emit intense red light after doping with Eu3+ ions. fx1 Highlights • This work provides a novel lithium sodium diphosphate, Li 2 Na 2 P 2 O 7. • Li 2 Na 2 P 2 O 7 has an indirect bond gap of about 4.88 eV. • 1 mol% Eu3+ activated phosphor was synthesized by a solid-state reaction and its photoluminescence properties were studied. • Under 394 nm light excitation, Li 2 Na 2 P 2 O 7 :0.01Eu3+ exhibits a series of bonds corresponding to the 5D 0 →7F J (J = 0, 1, 2, 3, 4) of Eu3+ ion. [ABSTRACT FROM AUTHOR]

In this paper, the electronic properties and Schottky contact in graphene/MoS 2 (G/MoS 2 ) heterostructure under an applied electric field are investigated by means of the density functional theory. It can be seen that the electronic properties of the G/MoS 2 heterostructure are preserved upon contacting owing to the weak van der Waals interaction. We found that the n -type Schottky contact is formed in the G/MoS 2 heterostructure with the Schottky barrier height of 0.49 eV. Furthermore, both Schottky contact and Schottky barrier height in the G/MoS 2 heterostructure could be controlled by the applied electric field. If a positive electric field of 4 V/nm is applied to the system, a transformation from the n -type Schottky contact to the p -type one was observed, whereas the system keeps an n -type Schottky contact when a negative electric field is applied. Our results may provide helpful information to design, fabricate, and understand the physics mechanism in the graphene-based two-dimensional van der Waals heterostructures like as G/MoS 2 heterostructure. [ABSTRACT FROM AUTHOR]

In this paper the electronic confinement energy states of a radially modulated cylindrical nanowire are numerically calculated, assuming that the modulated section has finite length and its radius is greater than the remaining section of the nanowire. The Schrodinger equation is solved within the effective mass approximation using the finite element method to specify the necessary conditions for emersion of 3-dimensionally confined states and to investigate size and magnetic field dependence of the confinement energies. Our results show that for any local increment of nanowire radius, there is at least one bound state for each channel of angular momentum. The energies of bound states of higher angular momentum are shown to lie in the energy continuum of lower angular momentums. In addition, there is some level crossing and anti-crossing in the size dependence of confinement energies which can be explained on the basis of symmetry. It is observed that in the vicinity of the level anti-crossing, the oscillator strengths associated to intersubband transitions from ground state change dramatically and vanish for some specific width of modulation. [ABSTRACT FROM AUTHOR]

In this paper, the carbon-doped boron nitride nanoplate (C-BNNP) was prepared by pyrolyzing the precursor under N 2 and served as an excellent adsorbent for removal of Rhodamine B (RhB). The structure and composition of C-BNNP were characterized and its adsorption behavior for RhB was investigated. Compared with boron nitride nanoplate (BNNP) which was synthesized under NH 3 , C-BNNP displayed an enhancement of the adsorption capacity for RhB (833 mg/g). The adsorption activity was comprehensibly studied by kinetics, isotherm and thermodynamics. The adsorption kinetics followed pseudo-second-order model. The equilibrium adsorption data agreed well with the Langmuir isotherm. And the thermodynamics indicated that the adsorption process was a spontaneous, exothermic and physisorption process. In addition, the density functional theory was proposed that doping carbon in the BNNP decreased the chemical hardness of the adsorbent and enhanced the adsorption capacity of C-BNNP for RhB. [ABSTRACT FROM AUTHOR]

In this paper a five layer organic electronic device with alternately placed ferromagnetic metals and organic polymers: ferromagnetic metal/organic layer/ferromagnetic metal/organic layer/ferromagnetic metal, which is injected a spin-polarized electron from outsides, is studied theoretically using one-dimensional tight binding model Hamiltonian. We calculated equilibrium state behavior after an electron with spin is injected into the organic layer of this structure, charge density distribution and spin polarization density distribution of this injected spin-polarized electron, and mainly studied possible transport behavior of the injected spin polarized electron in this multilayer structure under different external electric fields. We analyze the physical process of the injected electron in this multilayer system. It is found by our calculation that the injected spin polarized electron exists as an electron-polaron state with spin polarization in the organic layer and it can pass through the middle ferromagnetic layer from the right-hand organic layer to the left-hand organic layer by the action of increasing external electric fields, which indicates that this structure may be used as a possible spin-polarized charge electronic device and also may provide a theoretical base for the organic electronic devices and it is also found that in the boundaries between the ferromagnetic layer and the organic layer there exist induced interface local dipoles due to the external electric fields. [ABSTRACT FROM AUTHOR]

In this paper, we systematically investigate the electronic structures of uncapped In(Ga)As nanoislands grown on pit-patterned GaAs(001) substrate by solving the Schrödinger equations with effective mass approximation, including composition profile (CP), band offset, strain induced deformation potentials, spin-orbit coupling and piezoelectric effect. For pure InAs epilayer, the shallow pit introduces red-shift to interband transition for all aspect ratios and the heavy-hole is localized by the confinement near the inclined hetero-interfaces in circular pit. For InGaAs alloy epilayer, the uniform CP and equilibrium CPs are considered. Due to the Indium segregation, the reduction of interband transition energy can be observed and the localized profile of heavy-hole moves upward visibly. Moreover, the strain relaxation analysis confirms better strain relaxation for nanoisland grown in shallow pit (tan β = 0.1) compared with same nanoisland grown on flat substrate. The results pave a guideline for designing site-controlled In(Ga)As nanoislands grown in pit for desired applications. [ABSTRACT FROM AUTHOR]

In this paper, electronic structure of a two dimensional elliptic quantum dot under the influence of external electric and magnetic fields are studied in the presence of Rashba and Dresselhaus spin-orbit interactions. This investigation is done computationally and to do this, at first, the effective Hamiltonian of the system by considering the spin-orbit coupling is demonstrated in the presence of applied electric and magnetic fields and afterwards the Schrödinger equation is solved using the finite difference approach. Utilizing finite element method, eigenvalues and eigenstates of the system are calculated and the effect of the external fields, the size of the dot as well as the strength of Rashba spin-orbit interaction are studied. Our results indicate that, Spin-orbit interactions, external fields and the dot size have a great influence on the electronic structure of the system. [ABSTRACT FROM AUTHOR]

Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200–800 °C). Intense and broad emission profiles were achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). UV–Vis spectroscopy revealed band gap energies (5.58–5.78 eV) higher than the excitation energies (~3.54 and ~2.98 eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details. [ABSTRACT FROM AUTHOR]

Recently, we have proposed the adaptive local basis set for electronic structure calculations based on Kohn–Sham density functional theory in a pseudopotential framework. The adaptive local basis set is efficient and systematically improvable for total energy calculations. In this paper, we present the calculation of atomic forces, which can be used for a range of applications such as geometry optimization and molecular dynamics simulation. We demonstrate that, under mild assumptions, the computation of atomic forces can scale nearly linearly with the number of atoms in the system using the adaptive local basis set. We quantify the accuracy of the Hellmann–Feynman forces for a range of physical systems, benchmarked against converged planewave calculations, and find that the adaptive local basis set is efficient for both force and energy calculations, requiring at most a few tens of basis functions per atom to attain accuracies required in practice. Since the adaptive local basis set has implicit dependence on atomic positions, Pulay forces are in general nonzero. However, we find that the Pulay force is numerically small and systematically decreasing with increasing basis completeness, so that the Hellmann–Feynman force is sufficient for basis sizes of a few tens of basis functions per atom. We verify the accuracy of the computed forces in static calculations of quasi-1D and 3D disordered Si systems, vibration calculation of a quasi-1D Si system, and molecular dynamics calculations of H 2 and liquid Al–Si alloy systems, where we show systematic convergence to benchmark planewave results and results from the literature. [ABSTRACT FROM AUTHOR]

It is an important topic to investigate the birefringence and reveal the contribution from ions to birefringence because it plays an important role in nonlinear optical materials. In this paper, the birefringence of carbonates with coplanar CO 3 groups were investigated using the first-principles method. The results show that the lead carbonates exhibit relative large birefringence. After detailed investigate the electronic structures, and Born effective charges, the authors find out that anisotropic electron distribution in the CO 3 groups and Pb atoms give positive contribution, while the negative contribution was found from fluorine atoms, meanwhile the Ca, Mg, and Cd atoms give very small contribution to birefringence. [ABSTRACT FROM AUTHOR]

The purpose of the paper is to establish the position of the tie-lines in the Sb-Sm-Se system at 450 ​°C and 620 ​°C, to determine the optical band gap of the phases. The Sb component is in equilibrium with the γ-Sm 2 Se 3-X -Sm 3 Se 4 (ST Th 3 P 4) solid solution region with α-Sm 2 Se 3. A continuous solid solution forms between the SmSb and SmSe (ST NaCl) phases, with which the Sm 3 Se 4 and Sm 4 Sb 3 phases are in equilibrium. The SmSb-Sm 3 Se 4 , Sm 3 Se 4 -SmSb 2 , SmSe-Sm 3 Sb 2 phases are also in equilibrium. In the Sb–Sm 2 Se 3 –Se system at 450°С, the tie-line passes between the Sb 2 Se 3 –Sm 2 Se 3 , Sb 2 Se 3 -SmSe 1.9 phases. In the Sb–Se system based on Sb 2 Se 3 , a solid solution of the subtraction type Sb 2-X □ X Se 3 (X ​= ​0–0.04) is formed. In the Sb-Sm-Se system, there is a solid solution of the substitution type along the cuts from Sb 2 Se 3 to the Sm 2 Se 3 (7 ​mol. % Sm 2 Se 3), SmSe 1.9 (4 ​mol. % SmSe 1.9) phases. The extreme compositions of solid solutions have a peritectic point. Due to the change in the position of the tie-lines in the Sb–Sm 2 Se 3 –Se system at 620 ​°C, additional phases appear in the equilibrium samples from the Sb 2 Se 3 –Sm 2 Se 3 section (annealing at 450 ​°C) when heated above 620 ​°C: Sb, SmSe 1.9. The optical band gap of the phases is: Sb 2-x Sm x Se 3 solid solution 1.17–1.19 ​eV, α-Sm 2 Se 3 1.62 ​eV. Optical properties of incommensurate SmSe 1.9 crystal that were investigated for the first time for this class of crystals indicate complex electronic structure that can be characterized as a multi band gap one, with at least two values of the band gap, 1.08 and 1.68 ​eV. Using optical spectroscopy, Sm ions in SmSe 1.9 are proved to be predominantly in 3+ oxidation state. Previously, the formation of ternary compounds in the system was reported in the literature. Carefully conducted research allows us to assert their absence. [Display omitted] • The conditions for obtaining equilibrium samples in the Sb-Sm-Se system were established. • Sb is in equilibrium with the γ-Sm 2 Se 3-X -Sm 3 Se 4 solid solution. • In the Sb-Sm-Se system at 450 and 620 ​°C, 18 tie-lines and 15 subsystems were identified. • In the Sb–Se system based on Sb 2 Se 3 , a solid solution of the subtraction type Sb 2-X X Se 3 (x ​= ​0–0.04) is formed. • The optical band gap of the phases is: Sb 2-x Sm x Se 3 solid solution 1.17–1.19 ​eV, α-Sm 2 Se 3 1.62 ​eV, SmSe 1.9 1.68 ​eV. [ABSTRACT FROM AUTHOR]

In this paper, the electronic structure, magnetic properties and half-metallicity of the CaMnO 3 /BaTiO 3 superlattice are investigated by employing the first-principle calculation based on density functional theory within the GGA or GGA + U exchange-correlation functional. The CaMnO 3 /BaTiO 3 superlattice is constructed by the cubic CaMnO 3 and the tetragonal ferroelectric BaTiO 3 growing alternately along (0 0 1) direction. The cubic CaMnO 3 presents a robust half-metallicity and a metastable ferromagnetic phase. Its magnetic moment is an integral number of 3.000 μ B per unit cell. However, the CaMnO 3 /BaTiO 3 superlattice has a stable ferromagnetic phase, for which the magnetic moment is 12.000 μ B per unit cell. It also retains the robust half-metallicity which mainly results from the strong hybridization between Mn and O atoms. The results show that the constructed CaMnO 3 /BaTiO 3 superlattice exhibits superior magnetoelectric properties. It may provide a theoretical reference for the design and preparation of new multiferroic materials. [ABSTRACT FROM AUTHOR]

In this paper, we report the effect of the tunnel anions on the ionic conductivity of Strontium-Lanthanum silicate apatites. The Sr 4 La 6 (SiO 4 ) 6 F 2 and Sr 4 La 6 (SiO 4 ) 6 O ceramics were prepared by the solid state reaction method. X-ray diffraction, NMR spectroscopy and Raman measurements were performed to investigate the crystal structure and vibrational active modes. Moreover, the electronic structures of the crystals were evaluated by the first-principles quantum mechanical calculation based on the density functional theory. Finally, the ionic conductivity was studied according to the complex impedance method. [ABSTRACT FROM AUTHOR]

In this paper we have investigated the structural, electronic and thermodynamic properties of tin oxide (SnO 2 ) using the full-potential linearized augmented plane wave method (FP-LAPW) within the framework of density functional theory (DFT) as implemented in the Wien2k package within the generalized gradient approximation (GGA) and GGA plus trans-blaha-modified Becke–Johnson (TB-mBJ) as the exchange correlation. From the electronic properties, SnO 2 has a direct band gap in ( Γ – Γ ) direction with a value of 2.86 eV. The quasi-harmonic Debye model, using a set of total energy versus volume calculations is applied to study the thermal and vibrational effects. Temperature and pressure effects on the structural parameters, such as thermal expansion, heat capacities and Debye temperature are investigated from the non-equilibrium Gibbs function. [ABSTRACT FROM AUTHOR]

The aim of “System Identification” is to determine modal and system properties of structural systems. This is while in “Damage Detection”, the identification of system characteristic matrices is as important as or even more important than the identification of frequency characteristics. Because of various constraints – i.e. difficulties in force excitation of structures due to their large size, geometry, and location – in practice only single excitation and partial measurement, at selected degrees of freedom, is possible. In this paper, a single dynamic load was applied to identify a structural system only along one of the degrees of freedom of the structure. Further, responses corresponding to a few degrees of freedom were also measured. To identify a system with this sort of restricted information, a new approach was introduced enabling identification of the structure׳s parameters of mass, damping and stiffness. Taking into account the significant effect of noise reduction in improving system identification accuracy levels, a noise reduction technique was also proposed. The accuracy of the method was also assessed against noise level and location of single excitation. It was shown that as noise level increases, identification errors will also increase (less than 3.5 percent). It was further observed that applying single force at the first storey of the flexural structure would yield the lowest error levels in the identification results. Later, the method׳s efficiency and precision were examined through the application of a “closed loop solution” to a six-storey flexural structure, and a four-span Pratt truss. The obtained results showed that the proposed method could act as an effective model in identification of system properties. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic and optical properties of K 2 CuBiX 6 (X ​= ​Br, Cl) are studied by the first principle calculation in this paper. Their structural and thermodynamic stabilities are guaranteed by the formation energy, binding energy and Born-Huang criterion. The results of elastic constants show that the two materials are ductile and can be applied in foldable optoelectronic devices. Besides, The calculated bandgap values are 1.03 ​eV and 1.44 ​eV for K 2 CuBiBr 6 and K 2 CuBiCl 6 , respectively, which is just in the ideal energy gap range of semiconductors. K 2 CuBiX 6 has very small effective mass advantageous to carrier transport. In addition, the optical properties analysis shows that K 2 CuBiX 6 has excellent light absorption properties in ultraviolet–visible wavelength. Due to their suitable bandgaps and good light absorption, K 2 CuBiX 6 has a promising application in solar cells and other optoelectronic devices. In this study, the perovskites K 2 CuBiX 6 (X ​= ​Br, Cl) are proposed as functional materials in solar cells. [Display omitted] • The K 2 CuBiX 6 (X ​= ​Br, Cl) are very suitable for photosensitive materials of solar cells. • The K 2 CuBiX 6 can be a potential candidate for excellent light absorbing material. • The K 2 CuBiX 6 is the structural and thermodynamic stabilities. [ABSTRACT FROM AUTHOR]

The paper presents two ways of improving the Jacobi–Davidson method for calculating the eigenvalues and eigenvectors described by eight-band k · p model for quantum dots and other low dimensional structures. First, the method is extended by the application of time reversal symmetry operator. This extension allows efficient calculations of the twofold degeneracy present in the multiband k · p model and other interior eigenvalues. Second, the preconditioner for the indefinite matrix which comes from the discretization of the eight band k · p Hamiltonian is presented. The construction of this preconditioner is based on physical considerations about energy band structure in the k · p model. On the basis of two real examples, it is shown that the preconditioner can significantly shorten the time needed to calculate the interior eigenvalues, despite the fact that the memory usage of the preconditioner and Hamiltionian is comparable. Finally, some technical details for implementing the eight band k · p Hamiltonian and the eigensolver are provided. [ABSTRACT FROM AUTHOR]

Abstract: The electronic and lattice dynamic properties of I 2–II–IV–VI 4 quaternary diamond-like semiconductors have a tight connection with their application in the area of solar cell absorption, thermoelectric conversion and so on. Structural configuration of these compounds is focused in present study, although previous researches always pay close attention to compositional modulation. In this paper, Ag2CdGeS4 polytypes (two types of Pna21, one type of Pmn21) have chosen as the representation to establish the relationship between cation ordering and physiochemical properties based on first-principle theory. The results show that cation arrangement practically affects their electronic and lattice dynamic properties such as bonding strength, band structure as well as their infrared spectrum. Due to different cation arrangement, two types (named model S and model P) of the same space group Pna21 demonstrate different properties. For both model P and Pmn21 of different space group, their related properties are alike because of similar cation arrangement. With the resulting cationic Born effective charges, the origin of the difference in electronic properties for three types of Ag2CdGeS4 can be reasonably explained from the viewpoint of vibrational polarization. [Copyright &y& Elsevier]

Abstract: Methylation of cytosines in the DNA is central to the epigenetic code. The patterns along the DNA formed by these chemical marks instruct the cell which proteins to express and their faithful maintenance after replication are vital to the organism''s life. Although Dnmt1 is the enzyme catalyzing the methylation reaction, it was found that UHRF1 (ubiquitin-like, containing PHD and RING finger domain 1) is the protein that actually recognizes hemi-methylated CpG sites. Nevertheless, the physical mechanism driving the strikingly robust distinction between hemi-methylated and unmethylated sites is not known. In this paper, we show that the large difference in the binding affinities of UHRF1 to these sites is possible not due to the presence of the methyl group itself but is a result of the accompanying changes in the distribution of the electrons around the cytosine ring. In particular, methylation reduces the dipole moment of cytosine and, as a consequence, unmethylated DNA in its unbound state in water is more stable than hemi-methylated DNA. Furthermore, the interaction energy of hemi-methylated DNA bound to UHRF1 with its surrounding is stronger than that of unmethylated DNA. Thus, the change in the electronic structure of cytosine upon methylation destabilizes the unbound state and stabilizes the bound state rendering discrimination with high fidelity possible. [Copyright &y& Elsevier]

Abstract: Silicon-on-insulator (SOI) devices have an inherent floating body effect which may cause substantial influences in the performance of SOI devices and circuits. In this paper we propose a novel device structure to suppress the floating body effect by using an embedded junction field effect transistor (JFET). The key idea in this work is to provide a path for accumulated holes to flow out of the body to improving of electrical performance. We have introduced a p+-Si1− x Ge x buried region under the n+-Si1− x Ge x source and called the proposed structure as embedded JFET SOI MOSFET (EJFET–SOI). Using two-dimensional two-carrier simulation, the output and subthreshold characteristics of EJFET–SOI are compared with those of conventional SOI counterparts. The simulated results show the suppression of floating body effect in the EJFET–SOI structure as expected without consuming a significant amount of area. [Copyright &y& Elsevier]

Abstract: In view of CdS growth is very impotent for technological importance especially solar applications; synthesis of this material remains a topic of great interest for researchers by means of an economically and technically viable method. In the present paper, Cd/CdS/n–Si/Au–Sb sandwich structure has been grown by Successive Ionic Layer Adsorption and Reaction (SILAR) technique. For investigating the structural properties, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) measurements have been performed and it has been seen that films exhibit polycrystalline behavior. The capacitance–voltage (C–V) and conductance/w-voltage (G/w–V) characteristics of Cd/CdS/n–Si/Au–Sb structure have been investigated by considering series resistance and interface states effects. These measurements have been done in the −4V, 4V voltage range and in the frequency range of 10kHz–3MHz at room temperature. It is seen that, the series resistance (R s) and interface state density have been strongly depend on frequency. The barrier height, donor concentration, diffusion potential parameters have been determined from the linear C −2–V plot. The barrier height values are obtained between 0.495 and 0.796eV and doping density values have been ranged from 1.455×1014 to 1.999×1014 cm−3respectively. The capacitance–frequency (C–f) and conductance/w-frequency (G/w–f) characteristics of Cd/CdS/n–Si/Au–Sb structures have been measured at the various biases 0.00–0.14V at room temperature. The energy distribution of the interface states (N ss) and their relaxation time (τ) have been determined from the forward bias capacitance–frequency characteristics. The N ss and τ values have ranged from 2.01×1012 cm−2 eV−1and 9.68×10−4 s in (Ec-0.45)eV–2.86×1013 cm−2 eV−1 and 3.81×10−4 s in (Ec-0.75)eV, respectively. [Copyright &y& Elsevier]

Abstract: The main goal of this paper is to develop a novel approach for vibration control on a piezoelectric rotating truss structure. This study will analyze the dynamics and control of a flexible structure system with multiple degrees of freedom, represented in this research as a clamped–free–free–free truss type plate rotated by motors. The controller has two separate feedback loops for tracking and damping, and the vibration suppression controller is independent of position tracking control. In addition to stabilizing the actual system, the proposed proportional–derivative (PD) control, based on genetic algorithm (GA) to seek the primary optimal control gain, must supplement a fuzzy control law to ensure a stable nonlinear system. This is done by using an intelligent fuzzy controller based on adaptive neuro-fuzzy inference system (ANFIS) with GA tuning to increase the efficiency of fuzzy control. The PD controller, in its assisting role, easily stabilized the linear system. The fuzzy controller rule base was then constructed based on PD performance-related knowledge. Experimental validation for such a structure demonstrates the effectiveness of the proposed controller. The broad range of problems discussed in this research will be found useful in civil, mechanical, and aerospace engineering, for flexible structures with multiple degree-of-freedom motion. [Copyright &y& Elsevier]

Abstract: In this paper, a framework of using h-adaptive finite element method for the Kohn–Sham equation on the tetrahedron mesh is presented. The Kohn–Sham equation is discretized by the finite element method, and the h-adaptive technique is adopted to optimize the accuracy and the efficiency of the algorithm. The locally optimal block preconditioned conjugate gradient method is employed for solving the generalized eigenvalue problem, and an algebraic multigrid preconditioner is used to accelerate the solver. A variety of numerical experiments demonstrate the effectiveness of our algorithm for both the all-electron and the pseudo-potential calculations. [Copyright &y& Elsevier]

Abstract: Hydrocarbon systems have been intensively studied via numerical methods, including electronic structure computations, molecular dynamics and Monte Carlo simulations. Typically, these methods require an initial structural model (atomic positions and types, topology, etc.) that may be produced using scripts and/or modeling tools. For many systems, however, these building methods may be ineffective, as the user may have to specify the positions of numerous atoms while maintaining structural plausibility. In this paper, we present an interactive physically-based modeling tool to construct structural models of hydrocarbon systems. As the user edits the geometry of the system, atomic positions are also influenced by the Brenner potential, a well-known bond-order reactive potential. In order to be able to interactively edit systems containing numerous atoms, we introduce a new adaptive simulation algorithm, as well as a novel algorithm to incrementally update the forces and the total potential energy based on the list of updated relative atomic positions. The computational cost of the adaptive simulation algorithm depends on user-defined error thresholds, and our potential update algorithm depends linearly with the number of updated bonds. This allows us to enable efficient physically-based editing, since the computational cost is decoupled from the number of atoms in the system. We show that our approach may be used to effectively build realistic models of hydrocarbon structures that would be difficult or impossible to produce using other tools. [Copyright &y& Elsevier]

Abstract: In this paper, a novel double-recessed 4H-SiC metal semiconductor field effect transistor (MESFET) with partly undoped space region (DRUS-MESFET) is introduced. The key idea in this work is to improve the DC and RF characteristics of the device by introducing an undoped space region. Using two-dimensional and two-carrier device simulation, we demonstrate that breakdown voltage (V BR) increases from 109V in conventional double recessed MESFET (DR-MESFET) structure to 144.5V in the DRUS-MESFET structure due to the modified channel electric field distribution of the proposed structure. The maximum output power density of the DRUS-MESFET structure is about 25.4% larger than that of the DR-MESFET structure. Furthermore, lower gate–drain capacitance (C GD), higher cut-off frequency (f T), larger maximum available gain (MAG), and higher maximum oscillation frequency (f max) are achieved for the DRUS-MESFET structure. The results show that the f max and f T of the proposed structure improve 95.6% and 13.07% respectively, compared with that of the DR-MESFET structure. Also, the MAG of the DRUS-MESET is 4.5dB higher than that of the DR-MESFET structure at 40GHz. The results show that the DRUS-MESFET structure has superior electrical characteristics and performances in comparison with the DR-MESFET structure. [Copyright &y& Elsevier]

Abstract: This paper presents a study of the synthesis and structural properties of the new pyrochlore-type Bi2−y Sr y Ir2O7 series. Ten compositions with 0.0≤y≤0.9 were prepared by solid-state reaction with thermal treatments at 873, 1073 and 1323K under atmospheric pressure conditions. Structural refinements from X-ray powder diffraction data by the Rietveld method show that all compounds of the Bi2−y Sr y Ir2O7 solid solution crystallize in a α-pyrochlore structure. The main structural difference when bismuth is substituted by strontium concerns the x position of the O1 (x, ⅛, ⅛). This substitution significantly increases the Bi/Sr–O1 distance and diminishes the Ir–O1 distance; this implies that the Ir–O1–Ir bond angle increases. With the Sr substitution, the IrO6 local configuration goes from a flattened trigonal antiprism, y<0.5, to an elongated one, y>0.5, passing through an octahedral array, y∼0.5. The electrical consequences of these structural changes observed in this system are qualitatively explained with electronic structure calculations, this behavior agrees very well with those observed in other pyrochlore systems A 2 M 2O7 (A=rare earth cations or Tl+, Pb2+, or Bi3+, and M=Ru or Ir). [Copyright &y& Elsevier]

Abstract: The passage of swift heavy ions through dielectric layers (SiO2 or SiON) on silicon, creates ion tracks in them. After the etching and filling of these ion tracks with a suitable material, a novel electronic structure acronymed TEMPOS – ‘Tunable Electronic Materials with Pores in Oxide on Silicon’ has been realized. Several electronic devices, both, active and passive, have been fabricated and systematically studied in the last few years. Sensors have also been successfully made and characterized using the TEMPOS structure as it offers a high surface to volume ratio resulting in fast response time and high sensitivity of the sensor. In continuation with these studies, in the present paper, ferrofluids have been inserted in the ion tracks to study their behaviour in confined geometry and for subsequently obtaining magnetic sensors. A comparative study has been done between the aqueous and non-aqueous ferrofluids. Insertion of the ferrofluids in the ion tracks exhibits a change in the I–V behaviour in the presence of a magnetic field which can be exploited for obtaining the above said sensor. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we consider band structure calculations governed by the Helmholtz or Maxwell equations in piecewise homogeneous periodic materials. Methods based on boundary integral equations are natural in this context, since they discretize the interface alone and can achieve high order accuracy in complicated geometries. In order to handle the quasi-periodic conditions which are imposed on the unit cell, the free-space Green’s function is typically replaced by its quasi-periodic cousin. Unfortunately, the quasi-periodic Green’s function diverges for families of parameter values that correspond to resonances of the empty unit cell. Here, we bypass this problem by means of a new integral representation that relies on the free-space Green’s function alone, adding auxiliary layer potentials on the boundary of the unit cell itself. An important aspect of our method is that by carefully including a few neighboring images, the densities may be kept smooth and convergence rapid. This framework results in an integral equation of the second kind, avoids spurious resonances, and achieves spectral accuracy. Because of our image structure, inclusions which intersect the unit cell walls may be handled easily and automatically. Our approach is compatible with fast-multipole acceleration, generalizes easily to three dimensions, and avoids the complication of divergent lattice sums. [ABSTRACT FROM AUTHOR]

Abstract: Calcium aluminates, compounds in the CaO–Al2O3 phase system, are used in high-temperature cements and refractory oxides and have wide range of potential technological applications due to their interesting optical, electrical, thermal, and mechanical properties. They are used in both crystalline and glassy form; the glass is an isotropic material while the crystalline materials may be highly anisotropic. This paper will consider two particular crystalline materials, CA2 and CA6, but the results should be applicable to all calcium aluminates. Although CA2 and CA6 crystals contain the same chemical species, Ca, Al, and O, the coordination and local environments of these species are different in the two structures and hence they show very different energy-loss near-edge structures (ELNES) when examined by electron energy-loss spectroscopy (EELS) in the TEM. The data obtained using ELNES can effectively provide a fingerprint for each compound and a map for their electronic structure. Once such fingerprints are obtained, they can be used to identify nano-sized particles/grains or material at interfaces and grain boundaries. In the present study, the local symmetry fingerprints for CA2 and CA6 structures are reported combining experimental spectra with electronic-structure calculations that allow the different features in the spectra to be interpreted. Al-L2,3 and O-K edge core-loss spectra from CA2 and CA6 were measured experimentally using electron energy-loss spectroscopy in a monochromated scanning transmission electron microscope. The near-edge structures were calculated for the different phases using the orthogonalized linear combination of atomic-orbitals method, and took account of core–hole interactions. It is shown that CA2 and CA6 structures exhibit distinctive experimental ELNES fingerprints so that these two phases can be separately identified even when present in small volumes. [Copyright &y& Elsevier]

Abstract: Recent data suggests that reactions of nitrite with ferric hemoglobin are potentially important in heme-protein dependent NO signaling. Our group and others are evaluating the role of reductive nitrosylation reactions in the generation of N2O3 as a signaling molecule. The latter reaction is hypothesized to involve reactions on NO, nitrite and methemoglobin to form N2O3 in an anhydrase reaction. Of potential importance to these reactions is the affinity of methemoglobin for nitrite and the reactivity of nitrite-bound methemoglobin with nitric oxide. In this paper, we review work related to the electronic structure of nitrite-bound methemoglobin and its dissociation constant. We present new data using electron paramagnetic resonance spectroscopy which confirm that methemoglobin has a much higher affinity for nitrite, under certain conditions, than reported in classical observations. Interestingly the affinity is greatest at lower pH and low nitrite:methemoglobin ratios. These data suggest additional interesting chemistry in the reaction of nitrite with ferric and ferrous heme species. Moreover, this reaction could serve as a paradigm for ferric heme reactions with nitrite. [Copyright &y& Elsevier]

Abstract: In this paper, we investigate a novel approach based on the combination of Tucker-type and canonical tensor decomposition techniques for the efficient numerical approximation of functions and operators in electronic structure calculations. In particular, we study applicability of tensor approximations for the numerical solution of Hartree–Fock and Kohn–Sham equations on 3D Cartesian grids. We show that the orthogonal Tucker-type tensor approximation of electron density and Hartree potential of simple molecules leads to low tensor rank representations. This enables an efficient tensor-product convolution scheme for the computation of the Hartree potential using a collocation-type approximation via piecewise constant basis functions on a uniform grid. Combined with the Richardson extrapolation, our approach exhibits convergence in the grid-size . Moreover, this requires storage, where r denotes the Tucker rank of the electron density with , almost uniformly in n. For example, calculations of the Coulomb matrix and the Hartree–Fock energy for the molecule, with a pseudopotential on the C atom, achieved accuracies of the order of hartree with a grid-size n of several hundreds. Since the tensor-product convolution in 3D is performed via 1D convolution transforms, our scheme markedly outperforms the 3D-FFT in both the computing time and storage requirements. [Copyright &y& Elsevier]

Abstract: In this paper we present several mathematical models that can be used to create approximate solutions of the three-dimensional Schroedinger–Poisson equation in layered semiconductor devices. A general algorithmic strategy that can be used to create efficient solution procedures for each of these models is described. Computational results demonstrating the accuracy and efficiency that can be obtained with the use of these models is presented. [Copyright &y& Elsevier]

Abstract: In this paper, we investigate the crystalline and electronic structure of Ni nanoclusters supported on Al2O3 and Cr2O3 obtained at different reduction temperatures. Their physical properties were characterized by powder X-ray diffraction, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy techniques. The global parameters of the active metal nanostructure such as average crystallite size and the microstrain are obtained by the generalized Fermi function for fitting the experimental X-ray line profiles. By X-ray absorption spectroscopy we evidenced a diminution of the coordination number in the first shell of the nickel atoms. In order to characterize the electronic structure of the active metal, X-ray photoelectron spectroscopy measurements were performed. Our results give additional information about the strong interaction between the metal clusters and oxide supports. [Copyright &y& Elsevier]

Abstract: α-Rhombohedral (α-rh) boron, which is the most stable of boron''s polymorphs at low temperatures, has p-type semiconductive properties. There have been some attempts to dope the interstitial sites with alkali atoms to create metallic or n-type semiconductive α-rh boron, but this has yet to be achieved. In a previous work, we proposed the codoping of α-rh boron with Li and P or As, and revealed from first principles calculations that B12PLi and B12AsLi could be synthesized and become narrow-gap semiconductors. The band structure suggested that the mobility of electrons might be greater than that of holes. In this paper, based on these prospective results, we selected a new combination of dopants, Li and O, and theoretically studied such compounds as B12OLi and B12O2Li. The results showed that both of these materials are metallic, while the reaction energies of the Li insertion into B12O and B12O2 are lower (more unstable) than with B12PLi and B12AsLi. It was proved that the differences in the electronic structures are caused by the dangling bonds of the dopant atoms, O, P and As. [Copyright &y& Elsevier]

In this paper, we propose a parallel orbital-updating based optimization method for electronic structure calculations. With our method, the solution of the minimization problem for the Kohn-Sham energy functional with respect to N orbitals is replaced by the solution of N independent minimization problems for the energy functional with respect to one orbital and the orthogonalization of the N updated orbitals. This new method allows a two-level parallelization. This feature makes our approach has a great advantage in large scale parallel computing. The numerical experiments show that our new method is reliable and efficient. Hence, our new method has a great potential for large scale electronic structure calculations on modern supercomputers. • Propose a parallel orbital-updating based optimization approach for KS model. • The new approach has a feature of two-level parallelization. • Provide two practical parallel orbital-updating based optimization algorithms. • Numerical experiments show that these new algorithms are reliable and efficient. [ABSTRACT FROM AUTHOR]