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The structural, elastic and thermodynamic properties of K 2 Te have been studied by the FP-APW + lo method as implemented in the WIEN2k code. The exchange-correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). The structural parameters are in good agreement with the available experimental and theoretical results. The Young's and shear modulus, and Poisson ratio have been calculated. The elastic constants and thermodynamic quantities under pressure and temperature are also calculated and elaborated.

Ab initio calculations based on density functional theory (DFT) were used to investigate the structural, electronic and optical properties of ZnS graphene based (GB) with N and H atoms as ligands. These studies were conducted using the generalized gradient approximation (GGA) by means of WIEN2k package and revealed how the electronic and optical properties of GB structures of ZnS, including density of electron states, the energy band structure, the dielectric function, the energy loss function, the refractive index, the reflection and absorption rates, are modified by the effects of H and N impurities. Band structure analysis indicated that ZnS GB is a semiconductor with direct band gap (3.4 eV) in Γ direction. Furthermore, it has been found that H (ligand) and N (ligand) atoms that bond to a Zn atom cause magnetic and half-metallic behaviors, and one or two electronic states appeared in the energy gap at down spin for H and N ligands, respectively.

In the present work, our aim is to verify the structural, electronic and magnetic properties of both systems Fe1.12Te and (R = Fe, X = Te and T = Ni, Co) in the P4/nmm structure. For this task, we use the density functional theory (DFT) as a theoretical tool integrated into wien2k code (Blaha 2001). The solid Fe1 − x Mx Te (M = Ni, Co) have been synthesised by Kazakov et al. (Chem. Met. Alloys 3, 155–160 2010). They have observed a systematic shift of the lattice parameters for both systems for M = Ni and Co till x = 0.1, then a secondary phase with the NiAs-type structure appeared when x passes 0.15. Fe1 − x Nix Te retains its structure in a concentration between x = 0.1 and 0.15, and Fe1 − x CoxTe retains its structure when x is between 0.05 and 0.1 (Blaha 2001).

Theoretical investigations on rutile SnO2 doped with V and Cr were performed by using recently implemented Tran and Blaha’s modified Becke-Johnson exchange potential model (TB-mBJ) based on density functional theory. The electronic, magnetic, dielectric and optical properties of V and Cr-doped tin oxide have been calculated by full-potential linearized augmented plane wave method (FP-LAPW) by WIEN2k code. The present works demonstrate accurate prediction of band structures and properties using the TB-mBJ model. The calculated values of magnetic moment, dielectric constant and refractive index of doped and undoped compounds agree well with the experimental results. The TB-mBJ model is a direct method without using empirical corrections and hence, the furnished data are useful in material modelling for spintronics applications.

Despite widespread use of pseudobinary alloys (GeTe)m-(Sb2Te3)n for manufacture of optical data storage memory interpretation of very fast crystallization and amorphization processes in these phase change materials (PCM) is still under discussion. To clarify the role of electron subsystem in unusual properties of PCM and to reveal the nature of their chemical bonding electron band structure calculations using WIEN2k program code were performed for compounds GeTe, Sb2Te3, GeSb2Te4 and Ge2Sb2Te5. Parameters of bond critic points in the electron density distribution for studied compounds and some related substances were obtained and analyzed. Characteristics of bond critic points inherent to basic PCM are established. They can be used as guide parameters for searching new perspective materials.

Optimal control of multi-electron systems is considered in the framework of the time-dependent density functional theory. For this purpose, the MATLAB package COKOSNUT is presented that aims at solving optimal quantum control problems governed by the Kohn–Sham equation. This package includes a robust globalized nonlinear conjugate gradient scheme and an efficient splitting procedure for the numerical integration of the nonlinear Kohn–Sham equations in two dimensions. Results of numerical experiments demonstrate the ability of the COKOSNUT code in computing accurate optimal controls. Program summary Program Title: COKOSNUT Program Files doi: http://dx.doi.org/10.17632/p5g5hznkpy.1 Licensing provisions: GNU General Public License 3 (GPL) Programming language: MATLAB Nature of problem: A method for solving time-dependent Kohn–Sham control problems. Solution method: NCG method and operator splitting methods. External routines/libraries: Libxc library [1]

In this paper, we have investigated the electronic structure and optical properties of the single crystal and two-dimensional (2D) structure of cadmium tungstate (CdWO4). This investigation includes calculation of the density of states (DOS), dielectric tensor elements and reflectivity. All the calculations have been done by full potential augmented plane waves plus local orbitals (FP-APW+lo) with Wien2k code. The calculated band gaps for the single crystal and 2D structure along [010] direction are 4.2 and 5.02 eV, respectively. The results show that in the 2D structure of CdWO4, the electron density of the surface oxygen atoms is much more than the electron density of the inside oxygen atoms. This difference in the density has the main role in the optical properties. The results of the dielectric tensor elements and reflectivity for the single crystal are in good agreement with the experimental values. The results of the dielectric tensor elements and reflectivity for the 2D structure in comparison with the single crystal have shown that the intensity and place of the calculated peaks reduced and shifted, respectively. These results can be related to the surface oxygen atoms and thickness of the 2D structure.

The first principle study of half-Heusler compounds RhCrZ (Z = Si, Ge) is performed in the framework of density functional theory (DFT). The compounds are found to have small band gap in the minority spin channel (spin-down). While the majority spin channel (spin-up) is metallic. Therefore, both compounds are half-metallic and 100 % spin polarized at Fermi level. Several properties including structural, mechanical, elastic, electronic, magnetic, and optical are computed using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2k simulation package. Equilibrium lattice constants for both compounds are found to be in the range 5.5–6.0 A. Elastic properties indicate the ductile nature of the compounds. The total magnetic moments for these compounds are approximately equal to 1μ B, i.e., MTot ≈ 1μ B. Hence, the compounds are weak ferromagnetic materials. We have calculated the complex dielectric function. Many optical properties including reflectivity, refractive index, conductivity, and absorption coefficients are obtained form dielectric function. Imaginary part of the dielectric functions shows that compounds are optically metallic and become transparent above 17 and 13 eV, respectively. It is also observed that compounds are more active in the infrared region.

In this paper, the energy levels of Yb 3+ ions in yttrium aluminum borate (YAB) crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2k package and a traditional fitting method using a more reliable computer package. The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers. Three types of likely mistakes in the previous researcher's paper, namely over fitting, incorrect use of irreducible representation, and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper. The electron paramagnetic resonance (EPR) parameters, which included g factors like g // and g ⊥ and hyperfine structure constants A // and A ⊥ , were also calculated through the perturbation method and compared with some observed values available in literature. There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation ( g // =4.000 and g ⊥ =1.391; A // =1032 and A ⊥ =360 in 10 −4 cm −1 for 171 Yb 3+ ) and those from the fitting approach ( g // =3.612 and g ⊥ =1.702; A // =867 and A ⊥ =470 in 10 −4 cm −1 for 171 Yb 3+ ).

The structural, electronic and magnetic properties and Kondo behavior of Ce 1 − x La x RuPO (x=0, 0.25, 0.5, 0.75 and 1) alloys are investigated using density functional theory by utilizing Wien2k package. The exchange-correlation potential is treated with the generalized gradient approximation (GGA). Moreover, the GGA+U approach (where U is the Hubbard correlation term) is employed to treat the f-electrons properly. We also present a comparative study between the electronic structure and magnetic properties of these alloys within GGA and GGA+U approaches. The calculated lattice parameters and bulk moduli of these alloys as a function of x are in the best agreement with Vegard's linear rule. The total and partial electron density of states and linear coefficient of electronic specific heat of these alloy within GGA and GGA+U are investigated and compared. The effect of La substitution on the Kondo behavior of CeRuPO compound is investigated.

The structural, electronic, magnetic, and thermodynamic properties of XFeSi (X = Gd, Tb, La) and GdRuSi compounds are investigated using density functional theory by the WIEN2k code. Using the first-principle procedure, the Hubbard parameter of Gd and Tb 4f electrons and La 5d electrons of XFeSi (X = Gd, Tb, La) and GdRuSi compounds is calculated. The structural and electronic and magnetic properties of these compounds within GGA and GGA + U approaches in the presence of spin-orbit coupling are calculated and compared. The calculated results indicate that the ferromagnetic phase is the most stable phase of XFeSi (X = Gd, Tb) and GdRuSi compounds and the nonmagnetic phase is the stable phase of LaFeSi. The magnetic moment of GdFeSi, GdRuSi, and TbFeSi compounds is due to Gd and Tb atoms. The calculated electronic band structures of these compounds show that these compounds have metallic behavior. Furthermore, the thermodynamic properties of these compounds using the quasi-harmonic Debye model as a function of temperature and pressure within GGA and GGA + U approaches are investigated.

This computational study is focused on the optical properties of Cu doped CdS for various supercell configurations. In this regard, Cd atoms are substituted by Cu atoms at various lattice positions and the results are almost similar except in the case of 2 × 2 × 2 supercell which involves more correlations and atomic interactions than those involved in other supercell configurations. Also by increasing the supercell size the optical properties are changed. The study has been performed by applying density functional theory in the Wien2K code using PBE-GGA approximations. The addition of Cu into CdS may be responsible for p-type character of CdS as illustrated by PDOS and TDOS calculations. The optical absorption increases in visible range but shows oscillatory trend in the UV region. However, doping of Cu into CdS lattice illustrates an enhancement in its electro-optical properties.

Delta phase in metallic plutonium is located at the transition from itinerant to localized electronic behaviour in the actinide series. Many models have been applied to this particular crystalline phase to unravel from first principles the elusive non-magnetic ground state observed experimentally. In this work structural and electronic ground-state properties are calculated where the possible magnetic states are compared to each other with the aid of a hybrid functional method as the high correlation approach (known as eece) implemented in the full potential LAPW code WIEN2k. Our results, obtained through a calculation procedure involving this high correlation model and the spin-orbit coupling term, show a feasible stability of the non-magnetic ground state of delta plutonium. The main contribution of the present work is the determination, under this level of theory, of approximate elastic constants of the non-magnetic ground state with zero total spin moment, thus confirming the mechanical stability of the crystal, which is in line with findings reported in previous works.

Strong relationship between direct X - X bonds and electronic properties in many thermoelectric materials is observed. In present work investigation on the relation between properties of such bonds in skutterudite-structured compounds and band gap size was performed. Various compositions of Co 1-x Rh x Sb 3 (x = 0 to 1) solid solutions were studied theoretically, using experimental structure data found in a literature as well as structures optimized through ab initio methods. Electronic structure of a set of pure CoSb 3 /RhSb 3 structures subjected to various external pressure conditions as well as solid solutions was obtained within DFT calculations using WIEN2k package. Topological properties of total electron density were determined under Bader's QTAiM formalism. Importance of charge transfer changes between Co/Rh and Sb atoms and their relation to the band structure were highlighted. According to presented results, strong influence of longer Sb-Sb bonds of Sb 4 ring on the band structure was explained, suggesting possible ways of CoSb 3 -RhSb 3 band gap engineering.

The article presents results of first-principles modelling of the ferrite/cementite interface with the Isaichev orientation relationship. Periodicity and close arrangement of the atoms in the two arrays (ferrite and cementite) for this orientation relationship indicates that the surface has low formation energy. Structural model of the interface was developed. The best conjugation of the two lattices is provided when the (101)c plane consisting of iron atoms in S-type positions is located at the interface. The supercell selected for ab initio modelling contained 64 atoms: 56 iron (28 in both ferrite and cementite parts) and 8 carbon atoms (in the cementite part). Simulation was performed in the framework of density functional theory method of the full-potential linearised augmented-plane wave with generalised gradient approximation in WIEN2k package. The optimum parameters of the system simulation were selected and volume optimization of structure was carried out. Calculated formation energy of ferrite/cementite interface is 0.594 J/m2, which is good agreement with both the theoretical and experimental data. There is a good correlation between the values of the magnetic moment and the interplanar distance for the iron atoms at the interface. Magnetic moment of iron atoms

The phase transition and structural, elastic, thermodynamic characteristics of CdSe1−xTex alloys for all compositions x (x = 0, 0.25, 0.5, 0.75, 1) in both hexagonal wurtzite (WZ) and cubic zinc-blende (ZB) are studied at zero K and zero pressure in emphasis of the Full Potential Linearized Augmented Plane Wave (FP-LAPW) approach, in accordance with the Density Functional Theory (DFT). This was inserted within the WIEN2k code, alongside a local density approximation (LDA) in order to consider the exchange-correlation functional. For all compositions the CdSe1−xTex alloys were found to be mechanically stable for both phases ZB and WZ, and the strongest material among all structures is CdSe. Our findings reveal that the relation between elastic constants and the Te concentrations is not linear. The induced phase transition from ZB to WZ is studied at zero K, and the corresponding volume collapses at the phase transition boundary are calculated for all compositions x (x = 0.0, 0.25, 0.50, 0.75). Our results show that for all compositions of the CdSe1−xTex alloys, the stable phase is zinc-blende. Furthermore, the elastic characteristics of ZB and WZ phases of CdSe1−xTex alloys, alongside elastic constants, bulk modulus and shear modulus were determined and assessed in comparison with other theoretical and experimental findings available. A positive relationship was observed. Keywords: Phase transition, Elastic properties, Thermodynamic properties, ZB and WZ

In this study, we demonstrate Zn1−x Fe x S (x = 0.0, 0.25, 0.50, 0.75, and 1.0) device applications by reporting electronic, magnetic, and optical properties, computed with Wien2k software, using density functional theory (DFT). The modified Becke and Johnson (mBJ) potential has been applied to accurately determine the material band gap. The presence of half-metallic ferromagnetism (HMF) is demonstrated. Moreover, the observed ferromagnetism is justified in terms of various splitting energies and the exchange constants. The Fe magnetic moment decreases from 4.0 μ B due to the strong p − d hybridization. A complete set of various optical parameters is also presented. The variation in the calculated static dielectric constant, due to Fe doping, is inversely related to the band gap that verifies Penn’s model. Moreover, the band gap of ZnS is tunable by the Fe doping, from ultraviolet to visible regions, depicting that the materials are appropriate for optoelectronic devices.

We study the structure of several standard and non-standard self-interstitial configurations in a series of hcp metals, by using Density Functional Theory as embodied in the computer codes SIESTA and WIEN2k. The considered metals include Be, Mg, Ti, Zr, Co, Zn, and Cd, thus spanning the whole range of experimental c/a ratios, different kinds of bonding, and even magnetism (Co). The results show the importance of low symmetry configurations, closely related to the non-basal crowdion, in order to rationalize the experimental data on self-interstitial structure and migration. Fil: Pasianot, Roberto Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina

To investigate the electro-optical properties of indium antimonide (InSb) for photo-voltaic applications, we performed first principles calculations using density functional theory (DFT). Our DFT calculations are based on full potential linearized augmented plane wave (FP-LAPW) method implemented by WIEN2K code. These calculations are carried out using generalized gradient approximation (GGA) and Tran Blaha modified Becke Johnson (TB-mBJ) approximation for exchange co-relation potential. All the calculations are performed with and without the addition of spin-orbit interaction (SOI) to GGA and TB-mBJ potentials. Addition of SOI gives the results very close to their experimental values and makes the calculations independent of k-points consideration. All the results are calculated by considering the temperature as high as 300 K. To the best of our knowledge, all the previously published theoretical results were calculated at 0 K and no such results have been reported at 300 K. In this article, we are reporting band structure, density of states (DOS) and the band gap dependent optical properties of InSb. The calculated direct band gap is 0.17 eV, refractive index is 3.79 and extinction coefficient as 3.22.

In this paper, we investigate the electronic and optical properties of MgO nanosheet in (100) and (111) directions. Our calculations carried out under the framework of density functional theory (DFT) exploiting WIEN2K code with Full potential, periodic boundary conditions, augmented plane-wave basis sets and GGA approximation. Electronic results indicate that MgO(111) nanosheet has an indirect band gap of 3.67 eV and MgO(100) nanosheet has a direct band gap of 3.14 eV. MgO(100) nanosheet exhibit more ionic bonding than MgO(111) and MgO(111) has more covalent bonding than MgO(100) nanosheet. Moreover, the optical results indicate that variation of dielectric function in x direction is more than the z direction. DOS and imaginary part of the dielectric function survey confirm semiconductor properties with different bang gap for structures. Comparing the imaginary part of dielectric functions in x and z directions for two structures, blue and red shift have been observed respectively. Our results indicate that these two nanostructures are transparent in a wide range of energy spectra and have low reflectivity.

For the first time, the structural and optoelectronic properties of a new complex formulated as CuBr2(C6H7N)2 (1) [trans-dibromidobis(3-methylpyridine-κN) copper(II)] were studied by density functional theory (DFT) calculations. They are performed using B3LYP through the Gaussian 09 program and also with full potential linearized augmented plane wave (FP-LAPW) methods within the Generalized Gradient Approximation (GGA) and Hartree-Fock (HF) theory by the Wien2k package. The neutral monomeric complex participates in a variety of non-covalent interactions, including hydrogen bonding and π stacking to create a 2D coordinate plane. The binding energy value of the non-covalent interactions responsible for the crystalline network formation of 1 were calculated using the method of dispersion corrected density functional theory (DFT-D). In this method, the independent smallest fragment (monomer) and subsequently the related network, including seven monomers bearing all non-covalent interactions were optimized. The results demonstrate that hydrogen bonds, especially non-conventional C–H···Br interactions, govern the network formation along the a and c axes. It can be mentioned because of these directed interactions, increasing of charge transfer along x and z directions results in increasement of the absorption and refractive index along y and z directions, and vice versa. The results of band structure show indirectly and directly the nature of the bandgap within GGA and HF, respectively. The bandgap value of CuBr2(C6H7N)2 is comparable to those of binary semiconductor compounds. DOSs spectra reveal that 3d Cu, 4p Br, and 2p C states play important roles in the optical transitions of the electrons. The calculated electronic absorption of the UV/Vis spectrum shows six major electron-transition bands derived from d → d (ligand field) n → n, n → π*, π → n, and σ → n MLCT and LMCT transitions. The calculated absorption spectrum of the titled complex through FP-LAPW within GGA method shows good consistency with the B3LYP/def2-TZVP/6-311+G(d,p) method. Our calculated birefringence results show that 1 has capability of nonlinear optical, which can be used in the nonlinear optoelectronic devices.

The fast advance in the semiconductor technology is very promising for optoelectronics devices and their future applications in Visible Light Communications (VLC) Systems. In fact, the following alloys In1-xAlxN, GaN1-xAsx, and ZnSe1-xOx are high efficient semiconductors for both solid-state lighting and solar cells. The work presented in this paper demonstrates the performance of the ternary system ZnSe1-xOx and binary relative (ZnSe and ZnO) as solid-state lighting. Theirs electronic and optical properties are discussed. The main functional parameters depending on the oxygen concentration are given such as: the band gap, the index of refraction, the dielectric function, the absorption coefficient, the network parameter, and the bulk modulus. Calculations are carried out by deploying the Ab-initio method approaches based on the density functional theory (DFT) within the local density approximation (LDA) and the generalized gradients approximation (GGA) using the Wien2K software package and the FP-LAPW method. The results obtained in this work corroborate those of the experimental results presented in the literature.

In order to acquire a reasonable description of the structural, electronic and optical properties of the perovskite compound $$\hbox {CsPbI}_{3}$$, first principle calculations have been computed by density functional theory implemented in the WIEN2k code. The calculations are presented within PBE-sol for exchange correlation functions coupled with modified-Becke–Johnson (mBJ) exchange potential. The (001) surfaces of $$\hbox {CsPbI}_{3}$$ for varying thicknesses have been constructed using the Structeditor program implemented in the WIEN2k code. The lattice constant, band gap and DOS have been computed. The $$\hbox {CsPbI}_{3}$$ bulk and surface exhibit a direct band gap located at the R symmetry point of the Brillouin zone. The band gap approaches experimental values when the exchange correlation function is coupled with mBJ. The optical properties of $$\hbox {CsPbI}_{3}$$ were computed in terms of dielectric properties, refractive index, extinction coefficient, absorption coefficient, conductivity, reflectivity and energy loss. The direct band gap nature and high-absorption power of the surfaces of $$\hbox {CsPbI}_{3}$$ in the (001) direction in the infrared, visible and ultraviolet energy range make it suitable for use in optical and optoelectronic devices.

Based on the density functional theory (DFT) implemented by the wien2k code which uses the full potential linearized augmented plane wave plus local orbitals (APW + lo) method, we have been able to study different physical properties of X[Formula: see text]PN2 (X = Li, Na) chalcopyrite such as structural, electronic, elastic and thermoelectric properties. According to our calculations, we have found that our structural and electronic parameters, such as the lattice parameter, energy bandgap, the tetragonal ratio, the displacement of the anions, are in very good agreement with the previous experimental and theoretical results. Based on the Voigt–Reuss–Hill approximations, we were able to compute the elastic constants: the compressibility, Young’s and the shear’s moduli, the average velocity of the elastic waves, the Debye temperature and the Poisson’s coefficient of the chalcopyrite LiPN2 and NaPN2. The elastic anisotropy is estimated and further illustrated by the three-dimensional (3D) direction of Young’s and Bulk’s moduli. Finally, using the semi-classical Boltzmann theory implemented in the BolzTraP code, we calculated the transport properties such as the Seebeck coefficient, the thermal electrical conductivity and the figure of merit of these materials.

In this article, we present first-principles calculations for structural and opto-electric properties of IIIAs (III = Al, Ga, In) in the zinc-blende phase. Our calculations are based on the full potential-linearized augmented plane wave method implemented in the WIEN2k code. We employed Perdew–Burke–Ernzerhof generalized gradient and modified Becke–Johnson approximations as exchange–correlation potentials. Our calculated structure parameters are found to be in reasonable agreement with the available literature. It was found that the inclusion of spin–orbit interaction effect shifts the conduction band minima towards the Fermi level and provides band gaps very close to their experimental values. The optical properties such as complex dielectric functions, complex refractive indices, reflectivities, energy loss functions, optical conductivities and absorption coefficients at varied frequencies were investigated in detail. We found that static real part of dielectric functions and refractive index decreases with increase in band gap. Our calculated critical point energies (eV) are consistent with the experimental results.

In this report, Fe2CoAl Heusler alloy is selected as a target to study site-preferences of atoms by first-principles calculations using WIEN2k code. It has been observed that Fe2CoAl (FCA) Alloy tend to form XA-I type structure (Hg2CuTi-type) which is more energetically favorable and also much stable compared to XA-II and XA-III type structures. Further, we observed that the total magnetic moment Mt (μB/f.u.) shows a strong dependence on site preferences of Co in all available Wyckoff sites. However, this compound does not show a half-metallic character but a metallic behavior has been observed for both spin direction at Fermi level EF, still, it can be used as the spin-polarized material for spintronics application.

Co2FeAl Heusler alloy was selected as a target to study L21 and XA ordering of atoms by first-principles calculations using WIEN2k code. It has been observed that Co2FeAl (CFA) Alloy tend to form L21 type structure,which is more energetically favorable and much stable compared to XA type structure. Further, we observed that the total magnetic moment (Mt) shows a strong dependence on site preferences of Fe in all available Wyckoff sites. However, this compound does not show a half-metallic character in both types of ordered structures still, it can be used as the spin-polarized material for spintronics application. Our results are opposite to usual site preference rule and approving the validity of the Slater-Pauling rule.

For acquiring a reasonable description of the structural, electronic, optical of CdSiAs2 pnictide semiconductor and its surface structure in (100) and (001) growth direction, first principle calculations have been computed by DFT implemented in WIEN2k. PBE- sol exchange correlation functions along with a more advanced technique namely, modified Becke Johnson exchange potential (mBJ-GGA) have been used for the calculations since mBJ gives results closer to the experimental value of band gap. Lattice constant, band gap and density of states (DOS) have been calculated. Bulk CdSiAs2 exhibits a direct band gap of 1.46 eV and major contribution to the density of states is from the Cd-d states while the surface structures of CdSiAs2 with 10 A thickness evidence metallic nature. While the reflectivities of both surfaces and bulk are optimal from UV to IR range, optical properties of bulk chalcopyrite CdSiAs2, computed in terms of dielectric constant, absorption coefficient, reflectivity and refractive index, show that absorption is high in ultraviolet and visible regions of energy spectrum thereby making it suitable for photonic and optical applications.

The chromium based fully compensated ferrimagnet, Cr2CoAl has been earlier proposed to show half-metallic ferromagnetism. In this paper, we thoroughly study the effect of atomic disorders on spin polarization, half-metallic character and magnetism in Cr2CoAl using Full-Potential Linearized Augmented Plane Wave method as implemented in WIEN2k code. Cr2CoAl exists in Inverse Heusler alloy structure with space group F4¯3m (No. 216). This study includes five types of disorders namely A2a-, A2b-, DO3a-, DO3b- and B2-type (as suggested by Singh et al for Inverse Heusler alloy). Our calculations predict Cr2CoAl as near half-metallic ferromagnet with 97% spin polarization. A2a-, A2b- and DO3a-type disorders exhibit high spin polarization of 98%, 99%, and 81%, respectively, whereas DO3b-and B2- type disorder exhibit 61% and 70% spin polarization, respectively. The energetics of these disorders suggest that DO3a-type disorder is more probable to occur but the high spin polarization in spite of disorder favors its application in spintronics devices. The total spin magnetic moment of Cr2CoAl is 0 µB, which increases with the disorders.

This chapter describes DFT band structure calculations that were performed in order to simulate the dielectric response of III-nitride semiconductors. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. For these DFT calculations, the standard tools found in Wien2k software were used. The novel modified Becke–Johnson (mBJ) exchange-correlation potential was also implemented, in order to improve the band structure description of these semiconductor compounds. The results from these calculations include band structure, density of states, and complex dielectric function for the whole compositional range. When compared with standard generalized gradient approximation (GGA), the predicted band gap energies for the novel potential were found to be larger and closer to experimental values. Additionally, the dependence of the most interesting features with composition was described by applying a Vegard law to band gap and plasmon energies. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through the whole compositional range (i.e., Al x Ga 1 − x N , In x Al 1 − x N , and In x Ga 1 − x N , with x = [ 0 , 1 ] ). Moreover, a detailed analysis of the collective excitation mode in the dielectric response coefficients (CDF and ELF) was performed by model based analysis. This reveals their compositional dependence, which sometimes departs from a linear behavior. Finally, an advantageous method for measuring the plasmon energy dependence from these calculations was also developed.

The structural, electronic and thermoelectric transport properties of topological Insulator (TI) LiAuS compound have been studied using first-principle calculation. In this work, we have employed full potential linearized augmented plane wave (FPLAPW) method as implemented in WIEN2k code and semi classical Boltzmann transport equations with constant relaxation time approximation. Our calculated results revealed that LiAuS is elastically and thermodynamically stable and ductile material. The negative value of band inversion strength gives indication about topologically nontrivial feature. The calculated values of Seebeck coefficient and power factor are 163.67 µV/K & 1.20×1012W/msK2, respectively. The value of figure of merit (ZT) at 1000K is 1.1 which makes LiAuS a potential candidate for thermoelectric application at high temperature.

Bu çalışmada XCuPb (X= Dy, Y) bileşiklerinin yapısal, manyetik ve elektronik özellikleri Yoğunluk Fonksiyonel Teorisi, FPLAPW metodu ile Wien2k kodu kullanılarak incelendi. Yapısal optimizasyon PBE-GGA potansiyeli kullanılarak yapıldı. Yapısal optimizasyondan birim hücre parametreleri ve toplam enerji belirlendi. Yapıların durum DOS eğrisi ve spin yönelimine bağlı olarak elektronik band grafiği çizildi. Elde edilen sonuçların deneysel veriler ile uyumlu olduğu görülmektedir. In this study, structural, magnetic and electronic properties of XCuPb (X = Dy, Y) compounds were examined by using Density Functional Theory, FPLAPW method and Wien2k code. Structural optimization was performed using PBE-GGA potential. Brim cell parameters and total energy were determined from structural optimization. Electronic band graph was drawn according to the state DOS curve and spin orientation of the structures. The results obtained are consistent with the experimental data.

In this communication we have calculated the structural, elastic and electronic properties of Tb-filled skutterudite TbFe4P12 using full potential linearized augmented plane wave method employed in WIEN2k. From our study of the structural properties, we found that our value of lattice constant is in excellent agreement with the experimental value and our results are seems better than the other theoretical reported value. The study of elastic properties reveals that the studied compound is elastically brittle. The value of anisotropic parameter and Poisson ratio shows that the compound TbFe4P12 is anisotropic and ionic in nature. Electronic band structure indicates the metallic behaviour which is in agreement with previous reported nature of the given compound.

We have performed the electronic structure calculations of SmB6 within the framework of density functional theory using the full potential linearized augmented-plane wave (FP-LAPW) approach as implemented in the WIEN2k package. Within the generalized gradient approximation (GGA), it is found that there are a large number of Sm 4f states at the Fermi energy (EF), which shows the metallic nature of SmB6. With the application of spin orbit coupling (SOC), there is a dramatic decrease in the Density of states (DOS) at EF akin to a pseudogap like feature. Further, the Sm 4f states split into j = 5/2 states appearing below EF, and j = 7/2 states above EF. In order to verify the robustness of the low energy band topology, we have also applied the modified Becke Johnson (mBJ) exchange potential incorporating SOC and found that the pseudogap feature is still present in the electronic structure suggesting metallicity of the bulk electronic structure. The results from GGA, GGA+SOC and mBJ+SOC calculations establish that the DOS near the EF is primarily contributed by Sm 4f states with some contribution from Sm 5d eg and B 2p states. Our findings could explain the bulk fermi surface observed in quantum oscillation measurements of SmB6.

The quest for 3d transition metals based materials over expensive rare earths to design new permanent magnets is of great economical and scientific interest. The parent Fe5SiB2 alloy shows in-plane magnetocrystalline anisotropy (MAE), however a good permanent magnet demands the MAE to be uniaxial. Therefore, we have considered Fe5-xCrxSiB2 alloys (x=0,1) and checked the effect of Cr-substitution at Fe4c site. The first-principles calculations in this regard have been performed by full potential linearized augmented plane wave (FPLAPW) method as implemented in WIEN2k. It is observed that the MAE per unit volume (K) calculated at T = 0 K changes from -0.1 MJ/m3 to 0.58 MJ/m3 on Cr-substitution in Fe5SiB2. Moreover, magnetic moment of Fe atoms near the substitutional site was substantially suppressed as compared to that in parent Fe5SiB2. Despite this relatively weak suppression in magnetization, substituted 4c site affects the local environment which leads to tuning of the MAE. Furthermore, we conclude that the positive MAE in Fe4CrSiB2 can be directly ascribed to the spin-orbit interaction. Hence the tailoring of MAE by adding small amount of easily available 3d TM, Cr in Fe5SiB2 can pave a new way for the synthesis of these type of materials at experimental front.

The electronic structures and optical properties of Li2SrTa2O7 belongs Ruddlesden-Popper layered perovskite family are studied by first-principles self-consistent local density calculations in its orthorhombic and tetragonal phases. The exchange-correlation potential were introduced within a framework of the generalizedgradient approximation (GGA). In both phases, the conduction band minimum is at the zone center while the valance band is located at H and N high symmetry pointsfororthorhombicand tetragonal phases, respectively. The dynamic dielectric function, optical properties such as reflectance, refractivity and extinction coefficient for two phases are reported for energy range 0-50 eV. The variation in electronic and optical properties can be interpreted to attribute to higher symmetry, coordination number or Li, Sr and Ta atoms and packing density in tetragonal phase than in orthorhombic phase.

A detailed analysis of the theoretical x-ray absorption near-edge structures (XANES) for the boron and nitrogen $K$ edge in hexagonal boron nitride ($h$-BN) employing density-functional theory calculations is presented. The supercell core-hole method and the Bethe-Salpeter equation are used for the description of electron-hole interactions. The calculations are carried out with two different codes, the vasp and the wien2k codes, employing the projector augmented-wave and the full-potential linear augmented-plane-wave methods, respectively. We find close agreement between spectra obtained from the two codes and between calculations using the supercell core-hole method and the Bethe-Salpeter approach. All our calculations, as well as previous calculations using the ground-state structure, yield a single $2{p}_{{\ensuremath{\sigma}}^{*}}$ peak in the boron $K$-edge spectrum and hence fail to describe the experimental double-peak structure. We find that the inclusion of electron-phonon interactions is crucial to obtain the experimentally observed double-peak structure. We include these effects fully parameter free and ab initio using a one-shot sampling method and obtain excellent agreement with experiment.

In this work two high density functional theory (DFT) correlation methodologies, the so called DFT+U (or GGA+U) implementation and the exact exchange of correlated electrons (EECE), hybrid DFT functional (or one case of hybrid DFT), are tested to determine the mechanical properties of americium-II. For each case, the numeric value of their principal parameter is chosen ([Formula: see text] for the first case and [Formula: see text] for the second one) once the crystalline structure meets all the mechanical stability conditions. The results show that there is a range of values of [Formula: see text] and [Formula: see text] in which both methodologies generate a stable (experimentally correct) non-magnetic ground state, reaching approximately the same numeric value of the set of elastic constants of the cubic structure. However, only for the case of the hybrid functional results it is possible to show how the non-magnetic configuration is energetically favored, as compared to the ferromagnetic configuration. This happens around [Formula: see text], a value in agreement with a previous analysis made under the same methodology for the metal case Am-I. Following a detailed and deep analysis, it is possible to find a close interrelation between the electronic properties of the metal: its distribution of states around the Fermi level, the energy difference between the two possible spin configurations, and the mechanical response of the crystal. Also, it is possible to conclude that the effect of alpha parameter on the [Formula: see text] electrons can be used as a parameter to simulate the presence of an external pressure over the structure. For the comparison, the calculations were performed within the LAPW approximation in DFT as implemented in the WIEN2k code, with a finite deformation method.

In this work, we compare the structural, electronic and optical properties of the three most common phases (wurtzite, zinc blende, rocksalt) of ZnS by adopting the Density Functional Theory (DFT) implemented in the Wien2k code. We used the generalized gradient approximation (GGA-PBE) and the modified Becke-Johnson potential (TB-mBJ) to calculate the various properties. This study shows that ZnS phase wurtzite is thermodynamically stable, the phase blende and wurtzite present the same electronic and optical properties. These results are in agreement with experimental data.

In the current research, we perform a density functional theory study of C, Ti mono- doped (C-@GaN, Ti@GaN), and their co-doped GaN (C-Ti@GaN). We investigate the effect of C, Ti and their co-doping on the structural, electronic, magnetic, and optical properties using the Wien2K code. The formation energy of mono- and co-doped GaN is negative under the N-rich conditions and co-doped material is more stable than the mono-doped material. Optical absorption of mono-doped GaN is redshifted while the absorption of co-doped material is blue shifted. Our calculated results are in accordance with the already reported literature. Since, we did not find magnetism in the C-Ti@GaN material and because of blueshift in absorption spectrum; we suggest that co-doped GaN is more favorable for the UV optoelectronics, power electronics, and the UV solar cells applications than the co-doped materials.

In this paper we study the structural, the electronics and the magnetic properties of the perovskite YMnO3. The ab-initio calculations of this compound were performed using the full potential linearized augmented plane wave form with total potential (FP-LAPW) method in the context of the density functional theory (DFT) implemented in the Wien2K code. The potential for exchange and correlation has been addressed by the GGA approximation. The electronic properties show that the YMnO3 perovskite material exhibits a metallic behavior when using the GGA approximation. The Monte Carlo simulations study showed that the YMnO3 material undergoes a ferromagnetic to paramagnetic phase transition at critical temperature Tc = 145 K.

In this paper, we present structural, electronic and optical response for inorganic lead-free tin halide perovskites ASnX3 (A = Rb, K; X = Cl, Br) compounds, to examine their possible utilization as future photovoltaic materials. The structural optimization, energy band structure, density of states and exhaustive optical spectra for these perovskite compounds are delved using the Tran-Blaha modified Becke-Johnson exchange and correlation potential as implemented in Wien2k code. Optical performance of the compounds is accomplished through the investigation of real & imaginary dielectric tensor components, optical absorption, reflectivity and refractivity spectra. Direct band gap for RbSnCl3 (RbSnBr3) and KSnCl3 (KSnBr3) compounds is obtained as 1.46 (0.98) eV and 1.48 (0.93) eV, respectively which lies within standard photo-voltaic range. Results obtained in present computations are in decent agreement with earlier reported data, which firmly endorse the accuracy of present calculations. In addition, band gap reduction is perceived while switching from X = ‘Cl’ to ‘Br’ which has also revealed the enhancement in integrated absorption coefficient. Promising electronic and optical properties obtained for these perovskite compounds affirms their potential utilization in photo-voltaic and other opto-electronic applications.

The structural, elastic, mechanical, optoelectronic, and thermodynamics properties of InP, InSb, and their mixed ternary alloys, InP1-xSbx, in their zinc blende structure for 0 ≤ x ≤ 1, are studied. The “full potential linearized augmented plane wave (FP-LAPW) method framed within density functional theory (DFT)" as realized in WIEN2k computational code is employed for all calculations. The results of elastic constants for simulated structures of InP1-xSbx alloys are the first time computed in this study. The results of the elastic constants showed that the InP1-xSbx alloys, for all compositions of x, are brittle and mechanically stable above and beyond showing the strong anisotropic character as well. On the other hand, the obtained results of InP1-xSbx for lattice parameters, bulk modulus, and band gap energy exhibit their nonlinear character. Also, the optical properties are determined at the level of the mBJ scheme for an energy range from 0 to 40eV. However, the “quasi-harmonic Debye model” is used to investigate the thermodynamics properties for example Debye temperature, specific heat, entropy, and their dependence on pressure, and the temperature is also analysed for the mentioned alloys. Our computed results for optical band gap and absorption coefficients expose these alloys as suitable candidate materials for optoelectronics applications in the infrared as well as in the visible region.

The aim of this paper is to investigate the structural, electronic, optical and elastic properties of the cubic AlxGa1-xSb ternary alloy with their related binary compounds GaSb and AlSb. The calculations are performed within density functional theory (DFT) using full-potential linearized augmented plane wave (FP-LAPW) method as implemented in Wien2k package. It is found that the lattice parameter of the AlxGa1-xSb ternary alloy shown a non-linear variation with the Aluminum (Al) mole fraction. Beside, the band gap variations with the composition of the ternary alloy exhibit also a small deviation from the Vegard's law, and the obtained results confirm the semiconducting character of the studied materials. Furthermore, the optical properties of the materials are calculated and compared with the theoretical models and with the experimental data found in the literature where a good agreement is observed. The elastic properties of the studied alloys are also determined in this study and they are compared with other works available in the literature.

In this study, we have investigated the structural, electronic and magnetic properties of the Hf2CrZ (Z = B, Ga, In, Si, Ge, Sn) full Heusler materials in both Hg2CuTi and Cu2MnAl type structures. These investigations have been carried out by employing the first-principles computational method - full potential (FP) linearized (L) augmented plane-wave plus local orbital (APW + lo) - framed within the density functional theory (DFT) and embodied in WIEN2k computational package. Our investigations show that Cu2MnAl-type structures of the Hf2CrZ (Z = B,Ga,In, Si, Ge, Sn) Heusler compounds are more stable than that of Hg2CuTi-type ones. Our investigations also show that Hg2CuTi type structure of Hf2CrZ Heusler alloys demonstrates half-metallic character for Hf2CrZ (Z = B,Ga, In) with a value of the magnetic moment 1 μB and lower value for Hf2CrZ (Z = Si, Ge, Sn).

In this work, some physical properties of ScX (X = Sb and Bi) nano-layers are evaluated based on DFT employing Wien2k code within generalized gradient approximation in presence of spin orbit coupling. The band order and topological phase of ScX (X = Sb, Bi) bulks are investigated and then the topological nature of these bulks is examined by the investigation of surface states topological phase of ScX nano-layers with different thicknesses. The bonding type between the surface atoms of ScX nano-layers is also investigated. Furthermore, the optical properties of ScX nano-layers are investigated and compared. The results show the high contribution of intraband transitions and consequently high reflectivity and negative real part of dielectric function of these nano-layers near zero energy. The different responses of ScX nano-layers to the radiated electromagnetic waves in polarizations of parallel and perpendicular to their surfaces imply the anisotropic optical features of these nano-layers in x (or y) and z directions.