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Amorphous carbon (a-C) has become a promising material applied for optoelectronic devices. The requirement parameter that should be considered to develop the device is the electronic property of the structure composed. a-C materials are composed of a hybridization mixture of sp2 and sp3 orbitals. The new characteristic possessed by a-C must be studied to investigate its electrical properties. In this paper, the density functional theory (DFT) using Quantum Espresso package has been applied to generate and analyze the density of state and band structure of a system. Here, the amorphous structure of carbon is modeled to be a combination between one unit cell of graphene with sp2 hybridization and 2-unit cells of diamond, with sp3 hybridization. The result shows that the electronic property of the a-C proposed behaves as metal, which is experimentally supported by the electrically conductive properties of sp2-hybridization carbon. [ABSTRACT FROM AUTHOR]

The main aim of the present manuscript is analysis, and simulation different type silicene nanoribbons with edges modified by hydrogen, used in modern semiconductors. The focus of this paper is investigation the main characteristic and parameters of doping a Bi atom in the unit cell of silicene nanoribbons. The experiments are carried out with external electric field with intensity 0.1V/A. In our study we used Angstrom (A) for distance measurement, because the approximate orbital diameter of one electron in a hydrogen atom is smaller, the atomic lattice spacing in most crystals is of the same order. On the base of the conducted classification we proposed and studied two different atom configuration - the top configuration and the valley configuration. In our investigation we used density functional theory (DFT) and applied methods for synthesis and calculation of the formation energy of the doped system. The obtained result show that the optimal configuration is the top configuration. On another hand we calculated the state densities of the doped configurations and energy band of investigated structures. The contributions of the partial states Si(s), Si(p), Bi(s), Bi(p) are also analyzed. [ABSTRACT FROM AUTHOR]

Research of structures based on magnesium diboride (MgB2) is an urgent problem in connection with their interesting physical properties and wide potential in industry. The most interesting structures are in a form of nanotubes considered in [1] and a combination of MgB2 with carbon nanotubes [2] (the latter compounds are more promising [3]). Therefore, electronic properties of various cluster models are studied in this paper: the cluster model of layers of MgB2, non-carbon nanotubes with atoms of MgB2. The cluster models of magnesium diboride structures and models of non-carbon nanotubes are presented. A band structure calculation of magnesium diboride-carbon tubes is performed. A comparative analysis of obtained results and literature data is shown. This paper discusses an issue of further ab initio calculations of the structures, such as fullerenes with a full content of B. [ABSTRACT FROM AUTHOR]

Intermetallic compounds are known for their diverse behavior showing electronic, ferromagnetic, paramagnetic, and optical properties that correspond to vivid applications in the industrial and technological field. The main purpose of this paper is to calculate specific heat at constant volume and specific heat at constant pressure for CuZn using density functional theory (DFT) and the full potential linearized augmented (FP-LAPW) method as incorporated in the WIEN2K code. Thermodynamic quantities such as specific heat at constant volume CV, and at constant pressure CP are evaluated using the Quasi-harmonic Debye model. Further, variation of CV and Cp are plotted within the definite pressure and the temperature ranges vary from 0 GPa to 50 GPa and 0 K to 1000 K, respectively. The calculations of CV and Cp give valuable data for experimental studies. [ABSTRACT FROM AUTHOR]

In this paper, we report the systematic study of formation energy, electronic, and magnetic properties of Iron-doped Hydrogen-saturated Silicon Nanowire (Fe:H-SiNW) using the first principle density functional theory. The results were obtained by the generalized gradient approximation (GGA) approach and examined along (100) direction-oriented silicon nanowire with a diameter of 1nm. The results showed that H-SiNW is a nonmagnetic semiconductor, while Fe:H-SiNW is a ferromagnetic half-metal. This study revealed that H-SiNW doped by Fe impurity can form a new type of 100% spin-polarized material, which is potentially fascinating for nano-electronic and nano-spintronic devices. [ABSTRACT FROM AUTHOR]

The utilization of non-renewable energy source is expanding quickly which brings about a rising global warming and other ecological issues. To dispose of this perilous circumstance, the analysts put forth attempts to foster innovations that depend on inexhaustible sources. First principle computations of structural, band structure and optical properties of CdZnS2 semiconductors are concentrated in the current paper inside the system of density functional theory (DFT) and Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) encapsulated in Wien2k code. The full potential linearized augmented plane wave method (FP-LAPW) method is used for solving the basis sets. The band structure and density of states (DOS) are registered for that yield 1.37 eV band gap of this compound. The integrated absorption coefficient is 77.976 5548 (×104 eV/cm) is computed by the absorption spectra. All the electronic and optical properties prove that this compound is reasonable for photovoltaic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Beryllium chalcogenides (BeS, BeSe and BeTe) belonging to group II–VI compound semiconductor family crystallize in the zinc-blende structure with four-fold coordinated atoms. They have higher bonding energy and hardness, exhibit unusual electronic, mechanical, thermal, optical properties. These exclusive properties make them very useful for various technological applications including laser diodes, high efficiency photo-detectors. In this paper, we have applied the full-potential linear- augmented plane wave (FP-LAPW) method within the frame work of the density functional theory (DFT) for structural, electronic, and thermal properties calculations for Be chalcogenides. For the purpose of exchange-correlation energy (Exc) involved in Kohn–Sham calculation, the standard generalized gradient approximation (GGA) formalism has been utilized. Murnaghan's equation of state (EOS) has been used for volume optimization by minimizing the total energy with respect to the unit cell volume. With the knowledge of electronic density of states (DOS) and band structures, mechanical and thermal properties of Be chalcogenides have been estimated. The B0/G ratio for BeX chalcogenides which is greater than 1.75 is attributed to the ductile nature of the materials. An increase in positive Cauchy pressure (C12–C44), in support of strong metallic bond is observed in the range of 1.88 to 7.57 with an increase in chalcogen atomic number [ABSTRACT FROM AUTHOR]

There has been an enormous focus on low-dimensional layered transition metal dichalcogenides (TMDs) for new futuristic electronic device fabrication. In this paper, we report the density functional theory based calculations of electronic properties of two dimensional (2D) and one dimensional (1D) heterostructures of ZT-MoSe2/PdSe2. The Schottky barrier with p-type contact changes to n-type contact by applying an external electric field and finally into ohmic on further increase in the electric field. The dangling bonds present on the edges of the 1D heterostructure are important to decide its electronic structure which changes from metallic to semiconductor on edge passivation. [ABSTRACT FROM AUTHOR]

This paper presents the structural and optoelectronic behavior of ZnSiP2 compound theoretically. The calculations are performed using full potential linearized augmented plane wave method (FP-LAPW) within density functional theory (DFT) as embodied in WIEN2K code. For the accuracy of calculation, Perdew-Burke generalized gradient approximation (PBE-GGA) is used. Based on the energy bands, the forbidden band gap of ZnSiP2 was found to be 1.37 eV which is suitable for photovoltaic applications. The formation of bands are explained with the help of spectra of density of states (DOS) to determine the effect of Ge doping at Si site on the electronic structure. We have also performed the computations for ZnSi0.875Ge0.125P2. Energy dependent absorption spectra is also reported in this paper to highlight the possible utilization of these compounds in optoelectronic devices. [ABSTRACT FROM AUTHOR]

From our previous molecular orbital calculations using hybrid density functional theory for proton-conducting perovskite metal oxides, it was found that proton pumping effect is combined during proton-conduction, and covalent bonding change occurs in a diagonal line. It is known that pure perovskite metal oxides are regarded as boundary system. It is because they consist of the same unit structures. However, during proton-conduction, both local structural relaxation and local chemical bonding change must be taken into consideration. In this paper, the proton-conducting mechanism is explained from the different viewpoints of local structural relaxation and local chemical bonding change. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present results of both experimental and theoretical vibrational frequencies of normal modes and its vibrational assignments for betulinic acid methanol monosolvate molecule. FTIR spectra were recorded and collected in 4000-400 cm-1 spectral range with a resolution of 2 cm-1. For calculations, the molecule extraction from betulinic acid methanol monosolvate molecular crystal was based on typical fragmentation scheme and chemical connectivity. Knowing geometry of molecular crystal, the obtained geometry of molecule has been optimized and DFT calculation regarding IR frequencies for all 255 normal modes was calculated. All computations has been done using for all electrons a localized basis set of Gaussian type functions TZVP with local and gradient corrected functional BP86. Our calculated frequencies are compared with available experimental data and the agreement is quite satisfactory. Overall, this justifies the simulation scheme used for the title system. [ABSTRACT FROM AUTHOR]

Scanning transmission electron microscopes provide atomic-resolution images and electron-energy loss spectra of crystalline systems. Density functional theory is a “theoretical microscope” that provides energetically preferred structures and excitation spectra. This paper gives a summary of several applications that demonstrate the breadth and depth of new results that can be obtained from a synergistic application of the experimental and theoretical methods to a wide range of complex materials systems. [ABSTRACT FROM AUTHOR]

Recently, we have developed novel Eu(III) complexes with three β-diketonates and one asymmetric bisphosphine oxide whose light emission intensity is drastically increased. In this paper, these complexes are investigated by the density functional theory calculation. For these complexes, we can expect more asymmetric ligand field, favorable for the efficient light emission. [ABSTRACT FROM AUTHOR]

We study the polyfluorene crystal using computational modelling based on the density functional theory. We assume a geometry with two monomers per unit cell and periodicity along the polymer's backbone structure. The stable structure determined at these conditions is characterized by significant torsion angles between individual units. We calculate its optical spectra using the TDDFT method and find a gap of 2.73 eV which is in a very good agreement with the experimental value of 2.83 eV reported in our recent paper for a thermally annealed PFO film. [ABSTRACT FROM AUTHOR]

In this paper, we investigate structural, elastic and thermodynamical properties of quaternary CoFeTiSn Heusler alloy by means of full potential linearized augmented plane wave (FP-LAPW)-based analytical calculations using Density Functional Theory (DFT) within generalized gradient approximation (GGA). The alloy is found to exist in the B2-type cubic Heusler structure, which is very similar to Y-type (or LiMgPdSn prototype) structure with space group F43̄m (#216). The structural parameters have been evaluated by performing optimization of CoFeTiSn at ambient condition. The computed values of second order elastic constants (C11, C12 & C44) confirm the mechanical stability. The mechanical constants signify brittle and covalent bonding of CoFeTiSn. It is worth mentioning that elastic and thermodynamical properties have been reported for the first time. [ABSTRACT FROM AUTHOR]

In this paper, the interaction of thioglycolic acid (TGA) with CdSe atomic cluster have been studied using first principle calculations and experimentally synthesized using chemical route method. Density Functional Theory (DFT) have been used for all the calculations. Structural and electronic properties have been studied theorectically and results have been compared to the experimentally obtained micrographs from TEM microscopy. The most stable interaction of CdSe cluster is obtained with thiol group of TGA due to the high bond dissiciation energy between Cd-S than Cd-O. Theoretical calculations have been performed using Gaussian basis set approach. [ABSTRACT FROM AUTHOR]

Inthis paper, we studied the adsorption behaviour of a 3,4-ethylene dioxythiophene (EDOT) molecule on a graphene sheet. Monte Carlo (MC) calculation was performed to determine the lowest energysite of the adsorbate on the graphene substrate. The results obtained showed that there is a strong interaction with binding energies ranging from -11.56 to -14.89 Kcal/mol (-0.50 to -0.65 eV) for all configurations obtained. The average adsorption distance of the isolated EDOT molecule on the surface of the graphene sheet is 2.60 Å. The electronic properties of these organic-inorganic systems were further investigated using density functional theory (DFT) calculations. The resulting charge density difference of the nanocomposite reveals possible charge transfer which suggests chemisorption and the bandgap of 0.001 to 0.004 eV obtained indicates excellent electrical conductivity. In sum, this study shows that EDOT-graphene systems can be employed for electronic applications specifically for energy storage. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of Hubbard U (DFT+U) addition on structural and electronic properties of YBa2Cu3O7-δ superconductor. The calculation applies first principles calculation within Generalized Gradient Approximation for Perdew-Burke-Erzenhof for solids (GGA-PBEsol) functional using Density Functional Theory. Energy convergence was found at 400 eV cut-off and 4×4×1 k-point sampling. The DFT+U correction was applied on Cu 3d states at the range of U = 2, 4, 6 and 8 eV where U=2 eV shows the largest band gap difference. Using the GGA-PBEsol+U method, the structural and electronic properties of YBa2Cu3O7-δ were investigated such as its lattice parameters, band structure, the density of states and atomic population. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the electronic structure and half-metallic properties of full-Heusler compounds with X2TiZ (X = V, Cr, Mn, Fe, Co, and Ni; Z = Si, Ge) type structure using the density functional theory (DFT). The electronic band structures were calculated and the density of states for both up spin and down spin was studied to predict the half-metallic properties in these various compounds. One of the spins shows metallic properties while the other spin exhibits the semiconductor properties, making it attractive in practical applications. [ABSTRACT FROM AUTHOR]

In this paper we investigate the thermoelectric properties of Mg2Ge material using first principles pseudo potential method based on density functional theory and Boltzmann transport equations. The calculations show n-type conduction, indicating that the electrical conduction is due to electron. The electrical conductivity decrease with temperature; the negative value of Seebeck Coefficient also shows that the conduction is due to electron. In this paper we have calculated Seebeck coefficient, electrical conductivity and thermal conductivity. The thermoelectric properties of system have been calculated in this temperature range 100K-1200K.The value of Figure of Merit (ZT) of this material is also increasing with temperature and maximum value is 4.58×10-5. [ABSTRACT FROM AUTHOR]

A solution to low cost electricity has been provided by the innovation of Thin-film flexible photovoltaics or solar cells which include a wide variety of organic, inorganic and organic–inorganic solar cells laid over substrates that are flexible and offer high-throughput technologies. The highest efficiencies are exhibited by CIGS among all thin-film PV devices. Thus justifying it to be present as the most appropriate and optimal thin film PV material with an efficiency of 18.8 %. Ternary chalcopyrite compounds (CuGaSe2, CuInS2, CuInSe2, CuAlSe2) offer large optical absorption coefficient and act as an absorber in thin films solar cells. In this paper we have presented a Density Functional Theory calculation of Al-doped CuInSe2 thin film of vacuum size 10 Å offering a bandgap nearby to the bulk CuInSe2 thus stating its apt configuration. The analysis of electronic and optical properties of this system is deduced by Trans-Blaha Modified Becke Johnson (TB-mBJ) functional and the bandgap is observed to be 1.02 eV. By increasing the amount of Al in the system we can increase the bandgap to its suitable range of solar spectrum thus define the usage of this thin film in optoelectronic applications. [ABSTRACT FROM AUTHOR]

In the present paper effect of carbonyl group positionon the NLO response of selected chalcone derivatives has been discussed. The position of carbonyl group in chalcone chromophores plays a vital role in enhancing the NLO behavior of chalcones. To provide a strategy to enhance NLO response the theoretical calculations were carried out using density functional theory by employing B3LYP/6-31G(d) level of theory. The DFT calculations were carried out on eight chalcones with carbonyl group at different location in combination with donorgroup. The DFT results suggest that depending on the position of carbonyl group one can possibly use thiophene and benzene as electron donor/acceptor in NLO chromophores design. Also the donor group placed on phenyl ring is more effective to enhance NLO property in comparison with donor group substituted at thiophene ring. We also demonstrate that position of carbonyl group in chalcones can alter the nature of charge transfer from D-Ï€-A-Ï€-D toD-Ï€-Asystem. The flexibility to change the nature of charge transfer gives great opportunity to tune the NLO and physical properties of chalcone derivatives. [ABSTRACT FROM AUTHOR]

The present paper provides the theoretical information about structural stability, electronic and thermoelectric properties of monolayer and bilayer of SrS. To obtain these properties we have utilized the first principle investigation with the method of density functional theory (DFT). The obtained results of monolayer and bilayer provides the information that the materials in both the phases are dynamically stable with the indirect semiconductor behavior we also obtained the orbitals contribution using projected density of state (PDOS). Furthermore in this paper we have obtained the temperature based thermoelectric properties such as thermoelectric power (see-beck coefficient), thermal and electrical conductivity and finally the Figure of merit (ZT) by utilizing the semi-classical Boltzmann transport equations (BTE). [ABSTRACT FROM AUTHOR]

In the present paper, we investigate the electronic transport properties of hybrid biphenyl molecular junctions by employing ab-initio self-consistent density functional theory (DFT) and non-equilibrium Green’s functions (NEGF) technique. In the hybrid system, biphenyl molecule is bridging between different left and right electrodes via thiol (SH) and Copper (Cu) chemical groups respectively. In model A, hybrid biphenyl is connected to left and right pristine zigzag graphene nanoribbon (ZGNR) electrodes. In models B and C, hybrid biphenyl is connected to pristine ZGNR electrode in left side, while one-edge Cu-doped and both-edge Cu-doped ZGNR electrode in right side respectively. The higher current value is found for model C than that of models A and B for higher positive applied bias. Moreover, a very strong rectification effect has been revealed in models B and C. The DFT-calculated transmission characteristics further supports the observed current findings. Our results will provide a new scientific and engineering understanding to enable the rectifying performance that can be used for next generation nano-rectifier devices and other nano-electronic applications. [ABSTRACT FROM AUTHOR]

In this paper, the electronic and optical properties of nickel doped Barium titanate (BTO) nanostructures are presented using Density functional theory (DFT). The plane-wave-based density functional theory (DFT) calculations are performed using the Quantumwise ATK ver 11.8.2 with local-density approximation (LDA) and generalized gradient approximation (GGA) for both undoped and nickel doped Barium titanate nanostrucrures. The calculated band gap energies and optical spectra for the nickel doped Barium titanate nanostructures are compared with the undoped samples of the same. It is found that, the band gap energies of undoped barium titanate calculated by LDA and GGA varies from 4.6 eV to 5 eV. However, the band gap calculated for doped Barium titanate is found to be 0 eV for both LDA and GGA approximations. It is therefore, observed that the doping of Nickel results in a decrease in band gap energy of materials. [ABSTRACT FROM AUTHOR]

In the present paper the chalcone belonging to D-π-A type push-pull system has been synthesized and the single crystals were grown by controlled solution evaporation technique. The grown single crystals were subjected to NMR, FTIR and powder X-ray diffraction technique to confirm the compound. The linear optical cut-off was found to be at 442 nm. The SHG efficiency was determined in powder form and was found to be 1.57 times that of KDP. The titled chalcone was found to be stable up to 106 °C. The DFT calculations revealed that the intermolecular interaction assisted molecular alignment play a crucial role in SHG. The un-optimal alignment of the molecules in the crystal structure resulted in decreased intermolecular charge transfer in the crystal. The structure-property relation is presented based on the experimental and DFT calculations. [ABSTRACT FROM AUTHOR]

Three aromatic imines derived from ortho-amino and para-amino benzaldehyde with suitable primary amine were synthesized by standard methods. These resulted to the formation of one oxime compound and two Schiff bases which were named Syn-ortho-aminobenzaldoxime, ortho-aminobenzylidinaniline and para-aminobenzylidin-para-chloroaniline respectively. The structures of these imines were certain by physical methods as outlined in another paper under publication. The main aim of project was the determination of ionization constants pKa for acid conjugate bases of imines under stud by potentiometric titration method using 0.1 M HCl as a titrant. These allowed the determination of ionization constant at range of temperatures (288-328) K, Hence the thermodynamic parameters of ionization, processes namely ΔG, ΔH and ΔS were evaluated and discussed. All the experimental results were complemented with theoretical calculations using density functional theory (DFT), various types of descriptors as parameters were based on quantum mechanical handlings. The parameters tested which have the capability to represent the changes observed in the experimental pKa(s) are atomic and structural properties included Molecular properties like energies of HOMO and LUMO, hardness(η), chemical potential(µ), ΔHf, , dipole of molecule(DM), and electrophilicity index(ω). The pKa investigated had a relation with the values of each parameter of the studied compounds. Depending on these relations, three sets of parameters were originated for comparison between the AM1, PM3, and HF6-311G methods. They were derived by employing semi-empirical calculation exemplified with AM1 and the PM3 model, and an Abinitio method expressed by Hartree-Fock (HF) model performed at the 6-311 G(d, p) level of theory. [ABSTRACT FROM AUTHOR]

In this paper, the electronic properties of TiB2 and Ti2B are computed within the framework of Density Functional Theory (DFT) based on Linear Combination of Atomic Orbitals (LCAO) method. In the present calculations, the generalized gradient approximation (GGA) proposed by Perdew-Burke-Erenzerhof (PBE) and Becke's scheme are considered to treat the correlation and exchange effects respectively. TiB2 crystallizes in the hexagonal AlB2 type structure which is designated as C32 with the space group P6/mmm. While the crystal structure of Ti2B described in this paper is isomorphous to the body centered tetragonal (Al2Cu - type) structure with space group I4/mcm. [ABSTRACT FROM AUTHOR]

Nonlinear crystal lattices support delocalized nonlinear vibrational modes, which are exact solutions to the dynamic equations of motion dictated by the symmetry of the lattice and exist regardless of the type of interaction potential and vibration amplitude. Earlier, considering the space symmetry group of the fcc lattice, all one-component delocalized vibrational modes were derived, the dynamics of which can be described by a single equation of motion. Twelve such modes were found and their dynamics for the fcc Cu, Ni and Al was analyzed on the basis of ab initio and molecular dynamics modeling using two different interatomic potentials. This allowed one to assess the accuracy of the interatomic potentials demonstrating the best fitting with density functional theory, and, thus, suitable for numerical experiments in the considered field. In this work, we analyzed the nonlinear dynamics of two delocalized modes in an fcc copper crystal. From the results obtained, it can be concluded that the stability of the mode decreases with an increase in the initial amplitude, and also that the modulational instability leads to an increase in the average stress level at the moment of maximum energy localization. The paper discusses the possibility of the formation of discrete breathers as a result of modulational instability and their possible influence on the macroscopic characteristics of the crystal. [ABSTRACT FROM AUTHOR]

The In this paper we have investigated the stability of 2D monolayer BSb in air, in terms of interaction with oxygen molecule (O2). Present study is based on Density functional theory recommended that O2 molecule could separate to each other spontaneously on the surface of 2D monolayer of BSb, during the dissociation an exothermic process is happened there. The electronic band gap with and without oxygen is 0.31eV (direct) and 0.43eV (indirect). Also, we have investigated optical properties and obtained that in pure BSb higher absorption of photon energy in UV region and oxygen adsorbed BSb also higher absorption of photon energy in UV region. According to this oxidized 2D monolayer BSb is stable after some deformation in structure. [ABSTRACT FROM AUTHOR]

We report the transport characteristics of Fe(100)|Mg1-XZnXO(100)|Fe(100), a magnetic tunnel junction (MTJ), calculated using the ab-initio density functional theory, Landauer formalism and non-equilibrium Green’s function (NEGF) techniques. A monolayer of ZnO, inserted at the middle of four layers of rock-salt MgO (100) planes is found to enhance the tunneling magneto resistance of the MTJ device by approximately 250% as compared to that observed in pure MgO based devices. Our calculated I-V characteristics are presented in the paper. [ABSTRACT FROM AUTHOR]

2D monolayer BAs system has very interesting properties due to high thermal conductivity and bipolar magnetic property which is good candidates for spintronic devices. 2D BAs based electronic device however, are found to degrade upon exposure to air. In this paper, we have discussed the stability of atomic level of 2D BAs system in the terms of its interaction with oxygen (O2) molecule. Our calculations based on density functional theory suggest that the O2 molecule could spontaneously dissociate on the surface of monolayer BAs system. During the dissociation process it shows exothermic reaction and exothermic energy is 2.60 eV. The electronic band gap without and with O2 molecule are 0.77 eV and 0.68 eV with direct band gap. From the optical study it is found that, in pure BAs the higher absorption of photon energy in UV region but in oxygen adsorbed BAs higher absorption of photon energy shifted in IR as well as visible region. According to that, oxidized surface of monolayer BAs based electronic devices is slightly degradation in air. [ABSTRACT FROM AUTHOR]

Intermetallic Heusler alloys are amongst the most attractive half-metallic systems due to their high Curie temperatures and their structural similarity to binary semiconductors. In this paper, we report structural phase transition of ternary Half-Heusler compound YPdSb from face centered cubic lattice to hexagonal lattice under high pressure based on Density Functional Theory (DFT) within Generalized Gradient Approximation (GGA), we have used quantum espresso computer code in order to achieve our goal. We have reported lattice parameters of both FCC and hexagonal phases and also performed how total energy, electronic band structure and density of states (DOS) of this compound change under pressure. [ABSTRACT FROM AUTHOR]

In the present paper, we have presented electronic and transport properties of silicon nanowire (SiNW) using density functional theory. Electronic and transport properties are computed for a different diameter of zigzag structure. These nanowires show metallic nature at a nano-scale. With increasing in diameter SiNWs are becoming more metallic. Out of 1R, 2R and 3R zigzag SiNWs, 1R zigzag serves a potential applicant as a electronic and thermal conducting material. [ABSTRACT FROM AUTHOR]

2,7-Bis(4-Methoxyphenyl) 9,9-Dipropyl-9H-Flurene (2,7-BMDF) compound used as, biomedical inhibitor, fluorescent tag and a laser dye in other applied applications. Even though this laser dye is usually used in liquid phase, this is promoting to result in more optoelectronic material properties are testified in the literature. The energy levels of HOMO and LUMO of laser grade dyes has vast eects on the performance of OLED, DSSCs, and these methods of structured modification will a way to progress in many more advanced organic dyes in the forthcoming. In this paper we have calculated thermodynamic properties, HOMO, LUMO, energy band gap and molecular potential maps using Gaussian o9 with density functional theory of 6-311G basis set. These outcomes provide a deep understanding of structure of the molecule and electronic properties in different mediums characteristics for optoelectronic applications. [ABSTRACT FROM AUTHOR]

The distribution of the ratio of two normal random variables X and Y was studied from [1] (the density function) and [2] (the distribution function). The shape of its density function can be uni-modal, bimodal, symmetric, asymmetric, following several type of distributions, like Dirac Distribution, Normal Distribution, Cauchy Distribution or Recinormal Distribution. In this paper we study a different approximation for this distribution Z = X/Y, as a function of four parameters: ratio of the means of the two normal variables, ratio of the standard deviations of the two normal variables, the variation coefficient of the normal variable Y, and the correlation between the two variables. A formula for the Distribution function and the density function of Z is given. In addition, using graphical procedures we established singularity points for the parameters where the approximation given for Z has a non normal shape. [ABSTRACT FROM AUTHOR]

In the present study, we have performed ab initio calculations of vibrational properties of RbFeS2 compound utilizing density functional theory. Total and element specific phonon densities of states (PDOS) were calculated within a direct approach of harmonic approximation. We used phonon density of states to calculate lattice contribution to the specific heat. The calculated phonon density of states shows a large number of high-frequency vibrational modes of Fe and S atoms, which strongly restricts application of the Debye model for analysis of thermodynamical properties of RbFeS2. The results of the present paper could be used in a further estimation of magnetic specific heat of RbFeS2. [ABSTRACT FROM AUTHOR]

This paper reports the experimental and theoretical study on the structure and vibrations of 2-Methylphenyl boronic acid (2MPBA). The different spectroscopic techniques such as FT-IR (4000-400 cm−1) and FT-Raman (4000-50 cm−1) of the title molecule in the solid phase were recorded. The geometry of the molecule was fully optimized using density functional theory (DFT) (B3LYP) with 6-311++G(d, p) basis set calculations. The vibrational wavenumbers were also corrected with scale factor to take better results for the calculated data. Vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes obtained from VEDA 4 program. The calculated wavenumbers showed the best agreement with the experimental results. Whereas, it is observed that, the theoretical frequencies are more than the experimental one for O-H stretching vibration modes of the title molecule. [ABSTRACT FROM AUTHOR]

Single nanowire electrode devices have their application in variety of fields which vary from information technology to solar energy. Silver nanowires, made in an aqueous chemical reduction process, can be reacted with gold salt to create bimetallic nanowires. Silver nanowire can be used as electrodes in batteries and have many other applications. In this paper we investigated structural and electronic transport properties of Ag nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Ag nanowire have been studied theoretically. First of all an optimized geometry for Ag nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations respectively. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Bulk properties of Ag are in agreement with experimental values which make the study of electronic and transport properties in silver nanowires interesting because they are promising materials as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Ag nano wire reveals that silver nanowire can be used as an electrode device. [ABSTRACT FROM AUTHOR]

In this short paper, the authors report a new computational approach in the context of Density Functional Theory (DFT). It is shown how it is possible to speed up the self-consistent cycle (iteration) characterizing one of the most well-known DFT implementations: FLAPW. Generating the Hamiltonian and overlap matrices and solving the associated generalized eigenproblems Ax = λBx constitute the two most time-consuming fractions of each iteration. Two promising directions, implementing the new methodology, are presented that will ultimately improve the performance of the generalized eigensolver and save computational time. [ABSTRACT FROM AUTHOR]

This paper studies the effect of uniaxial (u-) strain on half-metallic (HM) properties of NiCrP and NiCrSi semimetal Alloy. The Study was done by First Principle Density Functional Theory (DFT) module by using Quantum Espresso Software Package. The half-metallic and ferromagnetic (FM) characteristic of NiCrZ maintain in wide range of uniaxial strain. The study shows that NiCrZ is very robust nature in the presence of u- strain. We expect that NiCrZ is a more reliable material for spintronic devices. [ABSTRACT FROM AUTHOR]

In this paper by means of ab initio, from the first principles, modeling, electronic properties of a monolayer and bilayer of graphene are studied. Calculations of electron density and band structure of these substances are carried out. For verification of obtained results, calculated values are compared with known experimental results from angle-resolved photoemission spectroscopy (ARPES). [ABSTRACT FROM AUTHOR]

There are a few structures available for the layered LiCoO2 cathode materials, with the metals in different atomic positions. In this study, first principles calculations based on density functional theory were used to evaluate two LiCoO2 structures with different Li+ and Co3+ atomic positions. The calculation were conducted using local density approximation and by comparing the total energy of both LiCoO2 hexagonal R-3m structure, Li+ has more tendency for being in the 3a Wyckoff position instead of 3b. The calculated band structures of each LiCoO2 structures were also presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the process of chemisorption of cis-butadiene rubber on the surface of oxidized graphene was studied using the density functional theory. The polymer is interacting to a quinone group, an oxygen bridge, and an OH group which was differently located on the surface of the graphene sheet. Based on the calculated value of ΔG298, the possibility of spontaneous formation of the bond between butadiene rubber and these functional groups was estimated. The features of the temperature dependence of the change in free Gibbs energy for thermodynamically possible coupled systems are considered. [ABSTRACT FROM AUTHOR]

In this paper, we propose an improved new methodology in energy conformation problems for finding optimum energy values. First, we construct the Bezier surfaces near local minimizers based on the data obtained from Density Functional Theory (DFT) calculations. Second, we blend the constructed surfaces in order to obtain a single smooth model. Finally, we apply the global optimization algorithm to find two torsion angles those make the energy of the molecule minimum. [ABSTRACT FROM AUTHOR]

In this paper, density functional theoretical method has been used to study the effect of pentavalent Ta5+ doped La1-xCa xMn O3 perovskite oxide with concentration x = 0.0, 0.125 and 0.25 on the crystal structure. It is found that the crystal structure remained as orthorhombic Pnma for all concentration x. The lattice constants, Mn-O distance and the cell volumes are found to be decreasing with increasing x due to smaller ionic radius of Ta ions. The Mn4+-O-Mn3+ bond angle on the other hand, increases to 169.490 from 160.040 of LCMO for x = 0.125 but decreases back to 160.990 for x = 0.25. The changes in Mn4+-O-Mn3+ bond angle affect the magnetoresistance ratio which reduce to 16.2 % for x=0.125 from 99.9 % for x=0.0 and 0.25. [ABSTRACT FROM AUTHOR]

In this paper, quantum chemical calculations of (2e)-3-(3-Bromo-4-methoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one were performed by using B3LYP and CAMB3LYP levels of density functional theory (DFT) with 6-311++G(d, p) basis set. Geometric parameters of the title molecule in the ground state were found to be in good agreement with experimental data.13C and ¹H NMR chemical shifts were calculated within GIAO approach which is one of the most common approaches. The frontier molecular orbitals (HOMO and LUMO) were simulated by the same levels. Nonlinear optical parameters (NLO) were also evaluated by determining of dipole moment, polarizability and first hyperpolarizability. All of calculations were carried out Gaussian 09 package program. [ABSTRACT FROM AUTHOR]

Using first principles density functional theoretical calculations, the present paper reports a systematic study of phonon dispersion curves in pristine carbon (CNT) and silicon nanotubes (SiNT) having chirality (6,6) in the armchair configuration . Some of the phonon modes are found to have negative frequencies which leads to instability of the systems under study. The number of phonon branches has been found to be thrice as much as the number of atoms. The frequency of the higher optical bands varies from 1690 to 1957 cm-1 for CNT(6,6) while it is 596 to 658 cm-1 for SiNT. [ABSTRACT FROM AUTHOR]

Indium tin oxide is widely used transparent conductor. Experimentally observed that 6% tin doping in indium oxide is suitable for optoelectronic applications and more doping beyond this limit degrades the optoelectronic property. The stoichiometry (In32-xSnxO48+x/2; x=0-6) is taken to understand the change in lattice parameter, electronic structure, and optical property of ITO. It is observed that lattice parameter increases and becomes constant after 6% tin doping that is in good agreement of the experimental observation. The electronic structure calculation shows that the high tin doping in indium oxide adversely affects the dispersive nature of the bottom of conduction band of pure indium oxide and decreases the carrier mobility. Optical calculations show that transmittance goes down upto 60% for the tin concentration more than 6%. The present paper shows that how more than 6% tin doping in indium oxide adversely affects the optoelectronic property of ITO. [ABSTRACT FROM AUTHOR]

We have performed first principle calculations for the CoIn2S4 sulfo-spinel compound in paramagnetic, ferromagnetic and antiferromagnetic phases using the full potential linearized augmented plane wave method within the frame of density functional theory. This paper presents the data concerning the crystal structure, electronic band structure and magnetic behavior of CoIn2S4. Obtained results are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]