Partial Density Of States Curves Research Articles

Microwave-assisted synthesis of nanostructured tin sulfide as a highly efficient visible-light active photocatalyst: Characterization, applications, and theoretical studies

In this study, nanostructured tin sulfide was synthesized using a facile microwave-assisted method. The as-prepared sample was further characterized via X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), UV–Visible Diffuse Reflectance Spectroscopy (DRS), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH) and Mott-Schottky analyses. Based on the results, the synthesized SnS is an n-type semiconductor and has a direct band gap of 1.32 eV. Photocatalytic activity of nanostructured SnS was then evaluated through degrading methylene blue (MB) under visible light in a cylindrical batch reactor. The results show that this highly efficient photocatalyst can degrade almost up to 83.06% of 14 mg/L pollutant within 10 min, which can be attributed to its relatively high specific surface area of 52.819 m2/g. In addition, the photocatalyst performance was studied from the isothermic, thermodynamic, and kinetic points of view. The results suggest that Fritz-Schlunder along with Baudu are the most appropriate models to describe the adsorption process (the first step of photochemical reactions), as they have the lowest error functions and highest correlation coefficients. Based on kinetic studies results, there is a good agreement between the pseudo-second-order adsorption kinetic model and our experimental data. Additionally, the corresponding structural parameters of SnS were compared by size-strain plot (SSP), and Williamson-Hall methods. Furthermore, a density functional theory (DFT) approach was conducted to get more insight into the electronic and structural properties of the SnS. In terms of the band structure, 1.35 eV of band gap energy (Eg) is obtained, which perfectly matches with the results of characterization tests (1.32 eV). Finally, the partial density of states curves indicate that the valence band maximum (VBM) is mainly generated from 3pS, 5sSn, and 5pSn states while the conduction band minimum (CBM) is made of 5pSn states. Consequently, the spin-up and spin-down curves are found to be highly symmetric, indicating the non-magnetic property of tin sulfide.

Ab-initio study of the structural, electronic, elastic and thermodynamic properties of Sc3XB (X=Sn, Al, Hf)

We have applied the pseudopotential plane wave method to study the effect of X element (X = Sn, Al and Hf atom) on the structural, elastic, electronic and thermodynamic properties of the ternary borides Sc3XB. We have employed the generalized gradient approximation (GGA) for the exchange and correlation potential. The equilibrium lattice constants and the bulk modulus and its pressure derivative are calculated and compared with available experiment and theoretical results. We have also predicted the elastic constants, Young's modulus (E), Poisson ratio (υ), shear modulus (G). SnBSc3 has the largest elastic moduli among the studied compounds. The contribution of the different bands was analysed from total and partial density of states curves. The bulk modulus, specific heats, and Debye temperature are calculated as a function of temperature and pressure using the quasi-harmonic Debye model.

First-principles study of structural, elastic, electronic and optical properties of cubic perovskite LiMgF3 for novel applications

Structural, elastic and optoelectronic properties of materials are important to identify their applications in technology. In the present paper LiMgF3 is investigated to obtain these properties using the highly accurate full-potential linearized augmented plane wave (FP-LAPW) method. The exchange correlation effects are included through the generalized gradient approximation (GGA) and modified Becke-Johnson (mBJ) exchange potential. The structural optimization of LiMgF3 is compared with previous results and is found to be in good agreement with those results. The predicted band structure shows an indirect (M-Γ) bandgap of 6.1 eV. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young’s modulus, Poisson’s ratio are calculated and based on these calculations it is found that this compound is elastically stable and brittle in nature. The contribution of different bands to the band structure is analyzed from the total and partial density of states curves. Optical properties like real and imaginary parts of dielectric function, refractive index, extinction coefficient, reflectivity, energy loss function, conductivity and absorption coefficient are presented. Based on the optical properties of the compound, it is predicted that LiMgF3 is suitable for optoelectronic devices.

The enhancement of hydrogen storage capacity in Li, Na and Mg-decorated BC3 graphene by CLICH and RICH algorithms

New hydrogen adsorption states on Li, Na, and Mg-decorated graphene-type BC3 sheet have been investigated by first-principles calculations. The structural, electronic and binding properties, metal binding and nH2 (n = 1–10) adsorption states of these systems are studied in detail with the Mulliken analysis, charge density differences, and partial density of states. To enhance the number of the adsorbed H2 molecules per metal atom, and also to generate the better initial coordinates for reducing the simulation time, we present two masthematical algorithms (CLICH and RICH). The tested results on BC3 sheet and boron-doped graphene (C30B2) show that these algorithms can increase the number of adsorbed hydrogen molecules by minimizing the computational time. It is seen that nH2 (n = 1–10) adsorbed Li,/Na and/Mg-decorated BC3 single- and double-sided systems are industrial materials for hydrogen storage technology, their adsorption energies fall into the acceptable adsorption energy range (0.20–0.60 eV/H2). It is concluded from the optimized geometries and charge density differences for the higher number of H2 adsorbed systems that not only decorated metal atom but also the sheet plays an important role in hydrogen storage process, because the boron atoms in the sheet expand the induced electric field between the adatoms and BC3 sheet. From Mulliken analysis, there is a charge transfer mechanism between H2 molecules and metal atoms. Moreover, the resonant peaks for the sheet, metal atoms and H2 molecules in partial density of states curves indicate the possible hybridizations. Additionally, these adsorption processes are supported by charge density difference plots.

First principles study of the ground state magnetic properties of hypothetical B2-Fe50Al50 multilayers

The ground state structural, electronic and magnetic properties of multilayers of B2 Fe-Al stoichiometric (Fe50Al50) phase were studied by first principles calculations in the framework of the density functional theory as a function of the number of layers. From the cohesive energy point of view all, the studied multilayers are more stable in the ferromagnetic state. The calculated equilibrium lattice parameter of the B2-Fe50Al50 phase in the multilayers is smaller than that in bulk. The calculations of the magnetic properties show an enhancement of the total magnetic moment of the B2-Fe50Al50 phase on going from bulk to multilayers structures. The total and partial density of states curves indicate changes in the electronic configuration of surface Fe atoms (relative to that observed in bulk Fe50Al50) in all the studied multilayers. For Fe atoms located at sites in the inner layers, there were observed significant modifications in their electronic distribution only for multilayers with low number of bcc unit cell layers (2 and 4). The increase of the magnetic moment of the multilayers is discussed in terms of the observed enhancement of the local magnetic moment of Fe atoms.

Theoretical study of the new zintl phases compounds K2ACdSb2 (A=(Sr, Ba))

The electronic structure and optical properties of K2SrCdSb2 and K2BaCdSb2 compounds are computed using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in WIEN2k code. In this perspective, the local density approximation (LDA), generalized gradient approximation (GGA) and Engel and Vosko approximation (EV-GGA) were used for the exchange correlation potential. The calculated band structure shows a direct band gap of about 0.344/0.20eV (LDA), 0.463/0.285eV (GGA) and 0.904/0.707eV (EV-GGA) for K2SrCdSb2/K2BaCdSb2 compounds. The part of different bands was scrutinized from total and partial density of states curves. There is strong hybridization between Sr-s and Sr-p states and also between Cd-d and Sb-s states in the valence band. The electronic charge density has also been studied in the (200) crystallographic plane. The K, Sr/Ba, Cd and Sb atoms shows ionic bonding. Besides this, the optical properties, including the dielectric function are obtained and analyzed in details.

Elastic and Optoelectronic Properties of KCdF3: ab initio Calculations through LDA/GGA/TB-mBJ within FP-LAPW Method

Ab initio calculations are performed on the electronic, structural, elastic and optical properties of the cubic per-ovskite KCdF3. The Kohn—Sham equations are solved by applying the full potential linearized augmented plane wave (FP-LAPW) method. The exchange correlation effects are included through the local density approximation (LDA), generalized gradient approximation (GGA) and modified Becke-Johnson (mBJ) exchange potential. The calculated lattice constant is in good agreement with the experimental result. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young's modulus and Poisson's ratio are calculated. KCdF3 is ductile and elastically anisotropic. The calculations of the electronic band structure, density of states (DOS) and charge density show that this compound has an indirect energy band gap (M—Γ) with a mixed ionic and covalent bonding. The contribution of the different bands is analyzed from the total and partial density of states curves. Optical response of the dielectric functions, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of 0–40 eV. The compound KCdF3 can be used for high-frequency optical and optoelectronic devices.

First-principles study of the electronic structure and optical properties of cubic Perovskite NaMgF3

The structural, electronic, and optical properties of cubic perovskite NaMgF3 are calculated by plane-wave pseudopotential density functional theory. The calculated lattice constant a0, bulk modulus B0, and the derivative of bulk modulus B′0 are 3.872 Å, 78.2 GPa, and 3.97, respectively. The results are in good agreement with the available experimental and theoretical values. The electronic structure shows that cubic NaMgF3 is an indirect insulator with a wide forbidden band gap of Eg = 5.90 eV. The contribution of the different bands is analyzed by total and partial density of states curves. Population analysis of NaMgF3 indicates that there is strong ionic bonding in the MgF2 unit, and a mixture of ionic and weak covalent bonding in the NaF unit. Calculations of dielectric function, absorption coefficient, refractive index, electronic energy loss spectroscopy, optical reflectivity, and conductivity are also performed in the energy range 0 to 70 eV.

First principle study of the electronic structure, Fermi surface, electronic charge density and optical properties of ThCu5In and ThCu5Sn single crystals

The electronic structure, Fermi surface, electronic charge density and optical properties of ThCu5In and ThCu5Sn single crystals are studied. The calculations are based on the full potential-linearized augmented plane wave (FPLAPW) method. The exchange and correlation potential is treated by the local density approximation (LDA) and generalized-gradient approximation (GGA), in addition the Engel–Vosko (EV-GGA) formalism was also applied. The DFT calculations show that these compounds have metallic origin. The contribution of different bands was analyzed from total and partial density of states curves. The values of the density of states at Fermi energy (N(EF)) for ThCu5In (ThCu5Sn) is 1.75 (1.63) states/eV unit cell. The bare electronic specific heat coefficient (γ) is found to be equal to 0.30 and 0.28mJ/mol-K2 for ThCu5In and ThCu5Sn, respectively. The Fermi surface of ThCu5In/ThCu5Sn is composed of three/four bands crossing along the R–Γ direction. The bonding features are analyzed by using the electronic charge density contour in the (101) crystallographic plane and it shows the covalent character of Cu–Cu and Sn/In–Cu bonds. The optical properties were also calculated and analyzed.

Ab initio study of the structural, electronic and optical properties of the fluoropervskite SrXF3 (X = Li, Na, K and Rb) compounds

An ab initio full-potential linear augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA), as implement in Wien2k code, has been used to study the structural, electronic and optical properties of the fluoropervskite SrXF3 (X=Li, Na, K and Rb) compounds. The calculated lattice constant and bulk modulus are in agreement with previous calculations. The calculated band structures show a direct band-gap (Γ–Γ). The contribution of the different bands is analyzed from the total and partial density of states curves. The dielectric function, refractive index and extinction coefficient are calculated. The origin of some of the peaks in the optical spectra is discussed in terms of the calculated electronic structure. The values of static dielectric constant ε1(0) is found to be increasing with a decrease in the energy band-gap.

First-Principles Study of Electronic Structure and Optical Properties of Cubic Perovskite CsCaF3

Electronic, structural and optical properties of the cubic perovskite CsCaF3 are calculated by using the full potential linearized augmented plane wave (FP-LAPW) plus local orbitals method with generalized gradient approximation (GGA) in the framework of the density functional theory. The calculated lattice constant is in good agreement with the experimental result. The electronic band structure shows that the fundamental band gap is wide and indirect at (Γ–R) point. The contribution of the different bands is analyzed from the total and partial density of states curves. The charge density plots show strong ionic bonding in Cs-F, and ionic and weak covalent bonding between Ca and F. Calculations of the optical spectra, viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are performed for the energy range 0–30 eV.

First-principles study of electronic and optical properties of cubic perovskite CsSrF3

We present first principles calculations of the electronic, structural and optical properties of the cubic perovskite CsSrF3 by using the full potential linearized augmented plane wave (FP-LAPW) plus local orbitals method with generalized gradient approximation (GGA) in the frame work of density functional theory. The calculated lattice constant is in a good agreement with the experimental result. The electronic band structure shows that the fundamental band gap is wide and direct at Γ point. The contribution of the different bands was analyzed from the total and partial density of states curves. The charge density plots show strong ionic bonding in Cs-F, ionic and weak covalent bonding between Sr and F. The calculated optical spectra viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of 0–30 eV.

Theoretical Studies of the Atomic and Electronic Structure of Mercury/Aluminium Oxide Interface

Density-functional theory (DFT) theory is conducted for the structural and electronic features at the Hg/Al2O3 interface by the analysis of optimal structural geometry, partial density of states (PDOS) and difference charge density. The two adsorption sites of on-top and hollow locations according to the symmetry is adopted to construct the associated interfacial models between Hg atom and free surface. The calculated studies show that the oxygen atoms near Hg atom in the Al2O3 surface, for both on-top and hollow sites, have the gathering effect by shifting toward Hg atom. But their interacting electrons at the interface exhibit different statues in terms of the PDOS analysis that there have no evolution tendency to form the bond between associated O and Hg atoms at the on-top site; and the occurrence of Hg-5d and O-2p overlapping orbitals reveals the strong covalent bond existed at the interface. The PDOS curves show that Al atom in the surface is not liable to contribute to the formation of corresponding bonds by mixing its electrons with Hg atom. Meanwhile, the calculated results derived from difference charge density are in good agreement with the PDOS analysis. The calculated results support some advanced atomic investigation on design a new sorbent refined from fly gas, especially improving the mercury removal from the flue gas.

DFT Studies of Low Concentration Substitutional Doping of Transition-Metals on Single-Walled Carbon Nanotube Surface

Using first principles-density functional theory, a theoretical study of the electronic properties of (5, 5) armchair single-walled carbon nanotube doped with transitions metals (Fe, Co and Ni) is presented. The generalized gradient approximation was used for the exchange-correlation potentials. The energy cut-off of 500 eV was adopted in the study. The main features of electronic band structure and density of states are shown. A systematic comparison of the density of states as well as band structures of pure and doped SWCNT is made. The contribution of the different bands was analyzed from the total and partial density of states curves. These metals are used as catalysts during synthesis of single-walled carbon nanotubes and hence, the choice we have made. Where data is available, the results are compared with previous calculations and with experimental measurements.

Electronic structure and optical properties of Sb 2S 3 crystal

The electronic and optical properties of Sb 2S 3 are studied using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in Wien2k. In this approach, the alternative form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EV-GGA) was used for the exchange correlation potential. The calculated band structure shows a direct band gap. The contribution of different bands was analyzed from total and partial density of states curves. Moreover, the optical properties, including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are all obtained and analyzed in detail.

First-principles study of the electronic and the optical properties of In 6Se 7 compound

The electronic and the optical properties of hexaindium heptaselenide In 6Se 7 have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k. In this approach, the alternative form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EV-GGA) was used for the exchange correlation potential. The calculated band structure shows a direct band gap (Z–Z). The contribution of different bands was analyzed from the total and the partial density of states curves. Moreover, the optical properties including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are all obtained and analyzed in details within the energy range up to 20 eV.

First principles calculations of structural, electronic and optical properties of BaLiF3

Abstract Structural and electronic parameters of the perovskite BaLiF3 are obtained from density functional theory using the full-potential linearized augmented plane wave method (FP-LAPW) within the local density and the generalized gradient approximations. Detailed comparisons are made with the existing measured values and with results obtained in previous theoretical studies and with experimental measurements. The calculated band structure shows a direct band gap (Γ–Γ). The contribution of the different bands was analyzed from total and partial density of states curves. We have presented the assignment of the different optical transitions existing in BaLiF3 from the imaginary part of the dielectric function spectra with respect to their correspondence in the electronic band. Finally we have presented a theoretical study of the high hydrostatic pressure dependence of the electronic properties of perovskite BaLiF3.

Full potential calculation of structural, electronic and optical properties of KMgF 3

A theoretical study of the structural, electronic and optical properties of KMgF 3 is presented using the full-potential linearized augmented plane wave method (FP-LAPW). In this approach, the local density approximation was used for the exchange-correlation potentials. First, we present the main features of the structural and electronic properties of this compound, where the electronic band structure shows that the fundamental energy gap is indirect. The contribution of the different bands was analysed from the total and partial density of states curves. The different interband transitions have been determined from the imaginary part of the dielectric function. The results are compared with previous calculations and with experimental measurements. The present work also deals with the behaviour of electronic properties, namely, the energy band gaps, and the valence bandwidth of KMgF 3 subject of hydrostatic pressures up to 30 GPa.

Ab initio total energy calculations of the optical properties of the CdSnP2 ternary pnictide semiconductor

Abstract The optical properties of a ternary CdSnP 2 semiconductor have been studied in the chalcopyrite structure using the full potential augmented plane wave plus local orbital method (FPAPW + lo ). First, we present the main features of the structural and electronic properties of this compound, where the electronic band structure shows that the fundamental energy gap is direct at the centre of the Brillouin zone. The contribution of the different bands were analysed from the total and partial density of states curves. Moreover, our calculated optical properties suggest that there is an anisotropic optical conductivity of this crystal along both principal directions E ⊥ c axis and E ∥ c axis. The different direct interband transitions have been determined from the imaginary part of the dielectric function.

Mass Effects on Optical Phonons in L1 2 -Ordered Pt 3 57 Fe and Pd 3 57 Fe

Inelastic nuclear resonant scattering spectra of 57Fe atoms were measured on Pt357Fe and Pd357Fe with the L12 crystal structure, and with the same crystallographic sites for 57Fe atoms. Phonon partial density of states curves for 57Fe were obtained from these spectra. In comparison to the non-dispersive Einstein-like optical modes in Pt357Fe, the optical modes in Pd357Fe are broader. This difference can be understood in terms of the difference in mass of Pd and Pt.