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This article introduces and develop a new area of transparent conducting material by doping GaN with two rare earth (RE) impurities (Eu, Sm). Our theoretical calculations confirm that the co-doped compound exhibits half-metallic ferromagnet (HMF) with 100% spin polarization at the Fermi level using GGA and mBJ. To determine which magnetic configuration is the most stable one, we compared the energy of ferromagnetic and antiferromagnetic states. Our results suggest that the ferromagnetic state is the most stable ground state. The exchange splitting energy and exchange constants N 0 α and N 0 β are calculated. Additionally, we determined the electron specific heat 'c'. It has a high optical transmittance and conductivity. These properties make GaN doped with double rare-earth impurities a potential material in optoelectronic and solar cell applications. For the calculations of mechanical, optical, and transport properties, the generalized gradient approximation + Hubbard U (GGA + U) and the modified Becke–Johnson (GGA-TB-mBJ) approximations were used. [ABSTRACT FROM AUTHOR]

Aerosols produced from the oxidation of volatile/semi-volatile organic compounds (VOCs/SVOCs), known as secondary organic aerosol (SOA), account for a significant fraction of atmospheric airborne particles. This paper reviews the current understanding of SOA formation from gas-phase oxidation with a focus on anthropogenic precursors and their reaction products from atmospheric simulation chamber studies. The review summarises the major reaction products derived from main groups of SOA precursors (e.g., alkanes, aromatics), SOA yields and the factors controlling SOA formation. We highlight that lab-derived SOA yield depends strongly upon, not only the concentrations of SOA precursors and oxidants but also simulation conditions. [ABSTRACT FROM AUTHOR]

In this paper, the structural, mechanical and optoelectronic properties of X 3 P 2 (X= Mg, Ca) have been investigated by using the first-principles calculation. The obtained results from the structural and mechanical properties reveal that our X 3 P 2 compounds are thermodynamically and mechanically stable. Moreover, the elastic constants and bulk modulus result imply that Mg 3 P 2 is ductile and Ca 3 P 2 is brittle. The calculated band structure reveals that our two compounds have a direct bandgap (Γ - Γ ) of 0.523 eV and 0.446 eV for Mg 3 P 2 and Ca 3 P 2 , respectively, from GGA. However, on using HSE06 hybrid functional the bandgap has been enhanced to 1.282 eV for Mg 3 P 2 and 1.092 eV for Ca 3 P 2 . Both compounds exhibit a high optical absorption in the visible region (≥ 10 5 cm - 1 ), making them potential candidate for photovoltaic applications. [ABSTRACT FROM AUTHOR]

This work aims to test the effectiveness of newly developed DFT-1/2 functional in calculating the electronic and optical properties of inorganic lead halide perovskites CsPbBr3. Herein, from DFT-1/2 we have obtained the direct band gap of 2.36 eV and 3.82 eV for orthorhombic bulk and 001-surface, respectively. The calculated energy band gap is in qualitative agreement with the experimental findings. The bandgap of ultra-thin film of CsPbBr3 is found to be 3.82 eV, which is more than the expected range 1.23-3.10 eV. However, we have found that the bandgap can be reduced by increasing the surface thickness. Thus, the system under investigation looks promising for optoelectronic and photocatalysis applications, due to the bandgap matching and high optical absorption in UV–Vis (Ultra violet and visible spectrum) range of electro-magnetic(em) radiation. [ABSTRACT FROM AUTHOR]

The electrical, optical, and transport properties of double-ordered Bi2CrMO6 (M = Zn, Ni) perovskites were studied in detail in this paper. The full-potential linearized augmented plane-wave (FP-LAPW) method was used to perform the calculations. The Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential and the generalized gradient approximation (GGA-PBE) are employed. The lattice constants (a and c) of both the compounds accord well with the known theoretical data. Similarly, our elastic property estimates revealed mechanical stability and ductile behavior for the materials under consideration (because of B/G > 1.75), where B and G defined the bulk modulus and shear modulus. Optical characteristics are calculated and presented as a function of wavelength. The transmittance reaches 60% at visible light and infrared regions. On analyzing the thermoelectric properties from the Boltzmann semi-classical transport equation at room temperature, the figure of merit (ZT) approaches the benchmark value of 1. The power factor (PF) is calculated; the compound Bi2CrNiO6 has a large value of almost ∼ 1.2 × 10 12 W / m K 2 s . [ABSTRACT FROM AUTHOR]

Knowledge of hygroscopic properties is essential to prediction of the role of aerosol in cloud formation and lung deposition. Our objective was to introduce a new approach to classify and predict the hygroscopic growth factors (Gfs) of specific atmospheric sub-micrometre particle types in a mixed aerosol based on measurements of the ensemble hygroscopic growth factors and particle number size distribution (PNSD). Based on a non-linear regression model between aerosol source contributions from PMF applied to the PNSD data set and the measured Gf values (at 90% relative humidity) of ambient aerosols, the estimated mean Gf values for secondary inorganic, mixed secondary, nucleation, urban background, fresh, and aged traffic-generated particle classes at a diameter of 110 nm were found to be 1.51, 1.34, 1.12, 1.33, 1.09 and 1.10, respectively. It is found possible to impute (fill) missing HTDMA data sets using a Random Forest regression on PNSD and meteorological conditions. [ABSTRACT FROM AUTHOR]

The optical spectra of gyrotropic α-Hg3S2Cl2 polymorph were calculated for the first time to give a deep insight into its band structure. The exchange–correlation potential was treated with the generalized gradient approximation and modified Becke–Johnson potential (MBJ) to improve the accuracy of electronic structure calculation. The detailed analysis of the low-energy electronic states near the Fermi level was conducted. The main contributions of the sulfur and chlorine p states are located at the top of the valence band, while the S/p and Hg/s states give main contribution to the bottom of the conduction band. The direct optical band gap of 3.19 eV is at the Г-points of Brillouin zone. The value of direct optical transitions, which was calculated by MBJ method, agrees very well with the experimental report on diffuse reflectance spectra. The reported structural and optical properties of α-Hg3S2Cl2 polymorph make it a potentially interesting compound for nonlinear optical applications. [ABSTRACT FROM AUTHOR]

In this work, we report on the synthesis of Ni-doped WO3 flakes by the hydrothermal method. The physical and chemical properties of the synthesized Ni-doped WO3 flakes were thoroughly investigated by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, photoluminescence spectrum, X-ray diffraction, X-ray photoelectron spectroscopy, and N2 adsorption–desorption measurement, thereby confirming the effect of Ni doping on H2S-sensing properties. The sensitivity to H2S gas of Ni-doped WO3 flakes showed short response/recovery times of 17 s/110 s, high stability, good selectivity, and low operating temperature of 250 °C. Due to the increasing surface defects and oxygen vacancies with the presence of Ni2+ ions in the structure of WO3 flakes, the Ni-doped WO3 sensor exhibited a better sensing of H2S gas than the pristine WO3 sensor. This result indicates that the Ni-doped WO3 flake structure is promising for detecting H2S gas as a selective, inexpensive, and outstanding sensor materials. [ABSTRACT FROM AUTHOR]

In the present work, we consider systematically the electronic and optical properties of two-dimensional monolayer germanium monosulfide (GeS) under uniaxial strains along armchair (AC-strain) and zigzag (ZZ-strain) directions. Our calculations show that, at the equilibrium state, the monolayer GeS is a semiconductor with an indirect band gap of 1.82 eV. While monolayer GeS is still an indirect band gap semiconductor under ZZ-strain, an indirect–direct energy gap transition can be found in the monolayer GeS when the AC-strain is applied. The optical spectra of the monolayer GeS have strong anisotropy in the investigated energy range from 0 eV to 8 eV. Based on optical properties, we believe that the monolayer GeS is a potential candidate for applications in energy conversion and optoelectronic technologies. [ABSTRACT FROM AUTHOR]

Using the augmented plane wave + local orbitals method with different approximation functionals, we investigate systematically the electronic, optical and elastic properties of stannite-type Cu2CdGeSe4. Among different approximation functionals, the modified Becke-Johnson (mBJ) potential with Hubbard-corrected parameter U (mBJ + U) gives the most reliable results on the electronic properties of Cu2CdGeSe4 in comparison with the experimental data. Elastic modulus, elastic constants and the Poisson's ratio of Cu2CdGeSe4 were calculated using the Elastic software package. Optical properties such as wide spectrum of absorbed photon energy, namely 1.3-27.2 eV, high absorption coefficient (above 104 cm−1) and optical anisotropy suggest the application of Cu2CdGeSe4 in solar cells. [ABSTRACT FROM AUTHOR]

The electronic band-structure of the ternary sulfide Pb2GeS4 was investigated by combining experimental and theoretical methods. Binding energy (BE) values of core electrons of Pb2GeS4 are measured employing X-ray photoelectron spectroscopy (XPS) for as-synthesized and treated with Ar+-ions crystal surfaces. The XPS measurements indicate that Ar+-ion treatment does not change the BE values of the core-level electrons of atoms constituting the Pb2GeS4 single crystal as well as peculiarities of the XPS valence band (VB) spectrum. The treatment does not cause changes in the crystal surface stoichiometry. The band-structure calculations based on density functional theory (DFT) reveal total density of states and partial densities of states of Pb2GeS4 within different exchange-correlation approximations. The best fit with the experiment is derived when the DFT calculations of Pb2GeS4 employ modified Becke-Johnson potential with Hubbard-corrected functional and taking into account spin-orbit (SO) interaction. The calculations indicate that top and upper portion of the VB is composed mainly by S 3p states, its central portion is formed by Ge 4p and S 3p states, while contributions of Pb 6s states dominate at its bottom with slightly smaller contributions of Ge 4s states as well. Contributions of unoccupied Pb 6p states dominate at the conduction band (CB) bottom. Regarding the occupation of the VB by Ge 4p and S 3p states, the theoretical data are confirmed experimentally by matching the XPS VB spectrum on a common energy scale with the X-ray emission spectra representing the valence S p and Ge p states. The present calculations yield that the VB maximum is positioned at the Y point, while the CB minimum at the Г point; this fact indicates that Pb2GeS4 sulfide is an indirect-gap material. The principal optical constants are also elucidated using the ab initio DFT calculations. [ABSTRACT FROM AUTHOR]

We report on results of first-principles density functional theory (DFT) calculations of the total density of states (DOS) and the partial densities of states of a quaternary TlInGe2S6 compound, a promising nonlinear optical material. The calculations are made using the augmented plane wave + local orbitals method employing the WIEN2k package. The DOS curves are calculated in different approaches for exchange-correlation potentials, and it has been established that the best coincidence with the experiment is achieved when modified Becke-Johnson exchange potential is used with correction parameter U and an account of the spin-orbit splitting effect. The present DFT calculations present that the S 3p states are the primary contributors to the TlInGe2S6 valence band, making the main input to its top and upper portion. The primary contributors to the central portion of the valence band of TlInGe2S6 are the Tl 6s and Ge 4p states, while its bottom is generated due to contributions of mainly the In 5s states with slightly smaller contributions of the Ge 4p states as well. The bottom of the conduction band is dominated by the unoccupied Ge 4s states. The conduction band minimum and the valence band maximum are located at the L point of the first Brillouin zone resulting in a direct band gap of the TlInGe2S6 compound. The key optical constants are elucidated for TlInGe2S6 based on the present DFT calculations. [ABSTRACT FROM AUTHOR]

Estimates of lung dose of submicron particles in the human respiratory system play an essential role in assessing health outcomes of aerosol exposure. The objectives of this study are to calculate the regional lung dose of traffic-generated particles by different metrics from exposure in outdoor and indoor environments and to identify main factors determining the lung dose. Particle number size distributions were collected in both indoor and outdoor environments in two unoccupied apartments from 22nd February to 30th April 2012 in Bologna, Italy. The whole lung doses of outdoor aerosols by number, surface area and mass at a traffic site were 1.0 × 1010 particles/h, 130 mm2/h and 1.9 μg/h, respectively. A majority of particles by number and surface area were found to deposit in the alveolar region (65%). The physical properties of particles such as shape, hygroscopicity and density play an important role in the calculation of surface area and mass dose due to shifting of the lung deposition curve. Particle number can predict well the regional dose by number, while PM2.5 and PM10 are good metrics for the prediction of surface area and mass dose. Good correlations between NOx and the surface areas and mass dose (r2 ~ 0.8) and number dose (r2 ~ 0.7) of submicron aerosols suggest that NOx may be a good indicator for predicting the health outcomes of traffic-generated aerosols. The doses of indoor sub-micrometre aerosols are less than those of outdoor aerosols by factors of 4.1 (for number), 2.7 (for surface area) and 2.1 (for mass). Due to traffic emissions, the lung dose of outdoor aerosols in the traffic area was much higher than that in the residential area by 5 times for number and surface area and 2 times for mass. A different exercise level (standing, walking, running and cycling) has only a slight influence on the whole lung deposition fraction of submicron aerosols but has a large effect on the dose due to differences in ventilation rate. [ABSTRACT FROM AUTHOR]