Search

In this work, we have examined the structural, phonon and anisotropic elastic properties of a hexagonal δ-WN compound via density functional theory. The obtained structural parameters and mechanical properties are in agreement with the other experimental and theoretical results. The present phonon dispersion curve and elastic constants indicate that the δ-WN compound is both mechanically and dynamically stable. The predicted elastic modulus shows that this compound possesses a high bulk modulus, shear modulus and Young’s modulus. The tabulated B/G and Poisson’s ratio have predicted that δ-WN has ductile behavior. According to the calculated minimum thermal conductivity, the hexagonal δ-WN compound can be used as thermal insulating material. Moreover, elastic anisotropy behavior has been analyzed with the different anisotropic indexes. The anisotropic elastic properties have been reported and discussed for the first time.

We report theoretical studies based on density functional theory within spin-orbit coupling to explore electronic structures, lattice dynamical properties of ZrSbTe and HfSbTe. With spin−orbit coupling included, our findings reveal that ZrSbTe and HfSbTe exhibit a semiconducting behavior with narrow indirect band gaps of 0.10 eV, and 0.15 eV, respectively. Besides, the lattice dynamical properties revealed that the explored materials based on antimonide−tellurides are dynamically stable. On the basis of electronic structures, the thermoelectric properties were computed using the Landauer-Buttiker formula by considering both electron and phonon contributions in the transport properties calculation. We employed Green’s-function method based on the Green-Kubo-Mori formula, where the thermoelectric properties such as the electrical conductivity σ and thermopower α were estimated in terms of the correlation functions. The present work could be viewed as a significant amendment of the electronic nature of ZrSbTe and HfSbTe that were reported to be metallic in literature.

*Deligöz, Engin ( Aksaray, Yazar ), In this paper, the hydrogen storage properties of the Li-decorated stable Hf2CF2 MXene layer, obtained by the exfoliation of Al from Hf2AlC and F-termination, are considered by using first-principles calculations based on Density Functional Theory. First, the stability characteristics of the host structure (Hf2CF2 layer) are examined by investigating bulk Hf2AlC. To enhance the adsorbed number of H2 molecules, the well-defined initial H2 coordinates are constructed by CLICH (Cap-Like Initial Conditions for Hydrogens) and Monte Carlo-based algorithms. After the geometry optimizations of the designed H2 systems on the Li/Hf2CF2 layer, the adsorption energies of nH2/Li/Hf2CF2 n = 1–10, 15, 20 and 25 systems are calculated, and the suitable values (0.2–0.6 eV/H2) are obtained up to 15H2. For n = 20 and 25 systems, which have adsorption energies of 0.15 eV/H2 and 0.16 eV/H2, respectively. The structural properties and adsorption geometries of these molecules are analyzed. Additionally, the partial density of the states, electron density difference maps, and Mulliken atomic charges are presented to identify the actual binding mechanism of the systems. The results reveal that the Li-decorated Hf2CF2 MXene layer can be preferred for the hydrogen storage applications due to its stable nature and the convenient adsorption characteristics.

The mechanical, dynamical, and thermodynamic properties of monolayer PbI2 were investigated comprehensively via first-principles calculations. The generalized gradient approximation was chosen for exchange-correlation effects. Thermodynamical properties, Debye temperature, sound velocity, charge density, Gruneisen parameter, and thermal conductivity were examined in detail. The present elastic constants and phonon spectra have shown that PbI2 is stable both mechanically and dynamically. It was revealed that the relationship among atomic mass, interatomic bonds, phonon scattering, specific heat, sound velocities, Gruneisen parameter, and Debye temperature cause low thermal conductivity. These results are matching with is predictions of Slack's theory.

The structural, electronic, elastic, and phonon properties of pristine Mo2ScC2 and surface terminated Mo2ScC2T2 (T = O and F) were investigated by employing density functional theory calculations. Generalized gradient approximation was used to model exchange–correlation effects. The electronic band structure was calculated using both Perdew–Burke–Ernzerhof and Heyd–Scuseria–Ernzerhof functional and found that all considered materials are metallic. Elastic constants, Young's moduli, shear moduli, in-plane stiffnesses, and Poisson's ratios were tabulated and showed that pristine Mo2ScC2 and surface terminated Mo2ScC2T2 satisfy the mechanical stability criteria. Furthermore, Mo2ScC2O2 has been found to be a significant candidate for ultrasensitive sensors due to its ultrahigh Young's modulus. The absence of the imaginary line in phonon band structures confirms the dynamic stability of Mo2ScC2, Mo2ScC2O2, and Mo2ScC2F2. Furthermore, Debye temperatures, phonon group velocities, thermodynamic properties, and Gruneisen parameters were calculated for Mo2ScC2 and Mo2ScC2O2. Finally, it is understood that Mo2ScC2 and Mo2ScC2O2 are suitable candidates for applications that require low thermal conductivity.

*Özışık, Hacı ( Aksaray, Yazar ) *Deligöz, Engin ( Aksaray, Yazar ), The characteristics of the electronic and phonon subsystems of lanthanum tetraboride (LaB4) studied using first-principles calculations. The calculated lattice parameters, as well as the positions of atomic, are satisfactorily consistent with the experimental data. The partial densities of states, band structure, Fermi surface, phonon dispersion curve of LaB4 are calculated and analysed. The reliability of the calculation results is confirmed by a satisfactory agreement between the calculated thermodynamic parameters of LaB4 (temperature changes in heat capacity, entropy, Gruneisen parameter and volume modulus) with experimental data.

We have investigated the structural, dynamical, elastic, and electronic properties of WGe2 and W5Ge3 compounds in different phases. We have considered the C11b (tetragonal, space group I4/mmm) and C23 (orthorhombic, space group Pnma) strukturbericht phases for WGe2 compound and D81 (tetragonal, space group I4/mcm), D8m (tetragonal space group I4/mcm) strukturbericht phases for W5Ge3 compound. The structural parameters, formation enthalpies, phonon dispersion curves, elastic constants, mechanical modulus, anisotropic factors, thermal conductivities, and electronic structures have been investigated using generalised gradient approximation within in the plane wave pseudopotential density functional theory. The calculated lattice constants are in a good agreement with the experimental data. The considered phases for WGe2 and W5Ge3 compounds have a metallic character. The results indicated that all phases for compounds are both mechanically stable and dynamically stable except for W5Ge3-D81. The anisotropy in some mechanical modulus has been investigated using several elastic anisotropy indexes and directional dependence of compressibility, Young’s moduli, shear moduli, and Poisson’s ratio.

We present a first-principles study of the phonon transport properties of the Half-Heusler NbCoSb compound. The single crystal elastic constants have been calculated using the stress- strain method. The mechanical properties such as bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and anisotropy factor are estimated using the Voigt–Reuss–Hill approximation. The Grüneisen parameters, phonon life time, and lattice thermal conductivity have been studied in detail. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. An analysis of the harmonic and anharmonic phonon dispersion and vibrational density of states reveal that, NbCoSb has a very low lattice thermal conductivity, hence, it is a candidate thermoelectric material.

WOS: 000423406900004, Methanol extracts of stem, leaf, and seed obtained from Pistacia terebinthus which are rich in phenolic compounds were used for the first time to produce chitosan-based antioxidative and antimicrobial films. All the produced films were characterized by FT-IR, TGA, DSC, SEM, contact angle measurements, and UV-Vis spectroscopy and mechanically. As was expected, incorporation of the plant extracts into chitosan films enhanced the antioxidant and antimicrobial activities effectively. Also, the elasticity of chitosan-seed and chitosan-stem films was improved. The eco-friendly nature of the produced blend films was determined through soil and water degradation analyses. All these findings lead to the conclusion that the produced blend films with Pistacia terebinthus extracts can be applied as alternative food packaging material.

First principles calculations are performed to systematically investigate the electronic, elastic, vibrational, and thermoelectric properties of the hexagonal, rhombohedral and monoclinic structures of CaGa2P2, CaGa2As2, and SrGa2As2 compounds. We adopt the generalized gradient approximation designed by Perdew, Burke, and Ernzerhof (PBE) for the exchange-correlation energy. The obtained structural parameters are agreement with the experimental values. The elastic and phonon properties were derived to discuss their stability in mechanical and dynamical. Mechanical properties were deduced within the Voigt-Reuss-Hill approximation. The brittleness and ductility are estimated by the values of Poisson's ratio and Pugh's rule (B/G). The electronic structures were used to illustrate the band characteristics. Minimum thermal conductivity has calculated and discussed. In addition, the transport properties, such as Seebeck coefficient, thermal conductivity, power factor, and electrical conductivity have been evaluated as function of energy relative to the Fermi level at various temperatures (T). We have also provided conservative estimates of the figure of merit (ZT). Overall, our results suggest potential new candidates of CaGa2P2, CaGa2As2, and SrGa2As2 for high thermoelectric performance.

WOS: 000402518800006, A comprehensive investigation of the structural, elastic, and lattice dynamical properties for ZrMo2 and HfMo2 with C14, C15, C36, and CeCu2 phases are conducted using density functional total energy calculations. The results have showed that C15 phase for both materials is energetically more stable than C14, C36 and CeCu2 phases. We have also estimated the mechanical behaviours of these compounds, including mechanical stability, bulk modulus, Young's modulus, shear modulus, Poisson's ratio, ductility, and anisotropy. Additionally, the lattice dynamical properties are analyzed and discussed exhaustively for these phases. The calculated properties agree well with available experimental and theoretical data.

WOS: 000375918800007, We have performed density functional calculations of the vibrational and thermodynamic properties of the ternary antimonides TiXSb, ZrXSb and HfXSb (X = Si, Ge). The direct method is used to calculate the phonon dispersion relation and phonon density of states for these compounds as well as their infrared and Raman active mode frequencies for the first time. Their dynamical stability is confirmed by phonon spectra. The lattice thermal conductivities of these compounds have been calculated from third-order force constants and plotted as a function of temperature. We have also evaluated the high temperature thermal conductivity by means of the Clarke's model and Cahill's model. Some selected thermodynamical properties, e.g. Gibbs free energy, entropy and heat capacity at constant volume are predicted theoretically and discussed. We have showed the relationships between thermodynamical properties and temperature., Aksaray University Research Project unit [2013-58], This work was supported by Aksaray University Research Project unit [Project number 2013-58].

*Sürücü, Özge Bayraklı ( Aksaray, Yazar ) *Deligöz, Engin ( Aksaray, Yazar ), The anisotropic mechanical properties of Tl4Ag18Te11 compound was investigated elaborately for the first time by using Density Functional Theory calculations with the Vienna Ab-initio Simulation Package in this work. Tl4Ag18Te11 compound was optimized in the I4mm space group and the formation energy was determined as a negative value that is the indication of the experimental synthesizability of this compound. The optimized crystal structure was employed for the calculations of the elastic constants and the obtained values revealed the mechanical stability of Tl4Ag18Te11 compound. The polycrystalline properties were determined such as shear modulus, Poisson's ratio, etc. In addition, the anisotropic elastic properties were presented. The direction dependent sound waves velocities, polarization of the sound waves, enhancement factor and the power flow angle were determined. The thermal conductivity studies were performed and the minimum thermal conductivity (0.259 ​W ​m−1K−1) and the diffusion thermal conductivity (0.202 ​W ​m−1K−1) were calculated. This study illustrates the capability of this compound for the thermoelectric materials.

*Özışık, Hacı ( Aksaray, Yazar ) *Deligöz, Engin ( Aksaray, Yazar ), The electronic, optical, thermoelectric, and dynamic properties of Pb 7 Bi 4 Se 13 have been investigated using first principles calculations. The existence of heavy elements, bismuth and lead, has required to consider the spin–orbit coupling as implemented in the second variational procedure. It was observed that the upper of the valence band region appears predominantly from Se-p states with an admixture of Bi- p and Pb- p states, while the CBM comes mainly from Bi- p states only. The calculated optical properties illustrate a small manifold direct and indi- rect inter-band transitions emerging in the visible region. Semi classic Boltzmann theory was then employed to determine the Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor. The phonon dispersion curve has been computed and explained. It can be deduced that the slight structural instability ob- served from phonon calculations is related to lower lattice thermal conductivity. Our findings were compared with the available experimental measurements, showing a good agreement.

WOS: 000454382200031, Density functional theory calculations are used herein to explore the effect of hydrogen on the electronic, mechanical and phonon properties of LaMgNi4 and its hydrides. The polycrystalline elastic moduli, Poisson's ratios and Debye temperatures are calculated based on the single-crystal elastic constants and Voigt-Reuss-Hill approximations. It is also found that all these materials are metallic behavior, ductile and anisotropic in nature. The mechanical anisotropy is discussed via several anisotropy indices and three-dimensional (3D) surface constructions. The effect of high temperature on the free energy, entropy, and heat capacity are also studied by using the quasi-harmonic Debye model. LaMgNi4 and its hydrides are found to be energetically, mechanically and dynamically stable. Also, they are thermodynamically stable and the order of phase stability is LaMgNi4H7 > LaMgNi4H4 > LaMgNi4H > LaMgNi4. In addition, the highest gravimetric hydrogen storage capacity is found to be 1.74 wt% for LaMgNi4H7. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

WOS: 000426254600002, In this study, the structural, electronic, magnetic, and mechanical properties of perovskite oxides PbM1/2Nb1/2O3 (M = Fe, Co and Ni) are investigated. The systems are treated in ferromagnetic order. The calculations are carried out in the framework of density functional theory (DFT) within the plane-wave pseudopotential method. The exchange-correlation potential is approximated by generalized-gradient spin approach (GGA). The intra-atomic Coulomb repulsion is also taken into account in calculations (GGA+U). We have considered two generalized-gradient spin approximation functionals, which are Perdew-Burke-Ernzerhof (PBE) and PBE for solids (PBEso1) for structural parameter calculations when it included Hubbard potential. Although the spin-polarized electronic band structures of PbCo1/2Nb1/2O3 and PbNi1/2Nb1/2O3 systems exhibit metallic property in ferromagnetic phase, a bandgap is observed in spin-down states of PbFe1/2Nb1/2O3 resulting in half-metallic behavior. The main reason for this behavior is attributed to the hybridization between d-states of transition metal atoms and p-states of oxygen atoms. The stability mechanically and the calculated mechanical properties by using elastic constants show that these compounds are mechanically stable in tetragonal phase and have anisotropic character mechanically., Ahi Evran University Research Project Unit [PYO-KMY.4001.15.001], This work was supported by the Ahi Evran University Research Project Unit under Project No. PYO-KMY.4001.15.001.

WOS: 000393880000002, The newly synthesised Ba2Sb4GeS10 compound is notable because of the interesting features of the quaternary Sb-containing materials. The first principle method has been used to determine the physical properties of this compound. In particular, the electronic structure has been analysed using both conventional GGA-PBE and HSE06 functional. The values of the band gap for PBE and HSE06 calculations were 1.324 and 1.84 eV, respectively. The calculated elastic constants were used to predict polycrystalline mechanical properties. The estimated Vickers hardness (2.7 GPa) values show that Ba2Sb4GeS10 is soft matter. Moreover, the vibrational properties of the compound have been studied. The calculation of the elastic constants and phonon dispersion curves indicates that the Ba2Sb4GeS10 compound is stable both mechanically and dynamically. Furthermore, the minimum thermal conductivity and optical properties, such as dielectric functions and energy loss function, have also been discussed in detail in this paper.

WOS: 000393723800015, First principles density functional theory (DFT) calculations have been used to investigate the structural, anisotropic elastic and electronic properties of ruthenium doped tungsten-diboride ternary compounds (W1-XRUxB2) for an increasing molar fraction of Ru atom from 0.1 to 0.9 by 0.1. Among the nine different compositions, W0.3Ru0.7B2 has been found as the most stable one due to the formation energy and band filling theory calculations. Moreover, the band structures and partial density of states (PDOS) have been computed for each x composition. After obtaining the elastic constants for all x compositions, the secondary results such as Bulk modulus, Young's modulus, Poisson's ratio, Shear modulus, and Vickers Hardness of polycrystalline aggregates have been derived and the relevant mechanical properties have been discussed. In addition, the elastic anisotropy has been visualized in detail by plotting the directional dependence of compressibility, Poisson ratio, Young's and Shear moduli. (C) 2016 Elsevier B.V. All rights reserved., Turkish Prime Ministry State Planning Agency [2011K120290], This work was supported by the Turkish Prime Ministry State Planning Agency under projects no. 2011K120290.

WOS: 000407392800007, In this study, we have investigated the electronic and optical properties of half-Heusler NiXSn (X = Zr, Hf) compounds under pressure by means of first principles calculations. The generalized gradient approximation is used to model exchange-correlation effects. We have estimated a transition from indirect band gap to direct band gap at 50 and 127 GPa for NiZrSn and NiHfSn, respectively. We have also plotted the static dielectric constant versus pressure for both compounds. The obtained results are in agreement with the available experimental and theoretical data.

WOS: 000340337200001, We used density functional theory (DFT) to study the structural, elastic, electronic, and lattice dynamical properties of tetragonal BiCoO3 applying the "norm-conserving" pseudopotentials within the local spin density approximation (LSDA). The calculated equilibrium lattice parameters and atomic displacements are in agreement with the available experimental and theoretical results. Moreover, the structural stability of tetragonal BiCoO3 were confirmed by the calculated elastic constants. In addition, the elastic properties of polycrystalline aggregates including bulk, shear and Young's moduli, and Poisson's ratio are also determined. The electronic band structure, total and partial density of states (DOS and PDOS) with ferromagnetic spin configuration are obtained. The results show that tetragonal BiCoO3 has an indirect band gap with both up- and down-spin configurations and its bonding behavior is of covalent nature. We compute Born effective charge (BEC) which is found to be quite anisotropic of Bi, Co and O atoms. The infrared and Raman active phonon mode frequencies at the Gamma point are found. The phonon dispersion curves exhibit imaginary frequencies which lead from the high-symmetry tetragonal phase to low-symmetry rhombohedral phase in BiCoO3. The six independent elastic constants, including bulk, shear and Young's moduli, and Poisson's ratio, complete BEC tensor and phonon dispersion relations in tetragonal BiCoO3 are predicted for the first time. Results of the calculations are compared with the existing experimental and theoretical data. (C) 2014 Elsevier Masson SAS. All rights reserved., Cukurova University [FEF2011D13, FEF2010BAP8], This work supported by Cukurova University under project number FEF2011D13 and FEF2010BAP8.

We have reported a first principles study of structural, mechanical, electronic, and thermoelectric properties of the monoclinic ternary thallium chalcogenes Tl2 MQ 3 (M=Zr, Hf; Q=S, Se, Te). The electronic band structure calculations confirm that all compounds exhibit semiconductor character. Especially, Tl2ZrTe3 and Tl2HfTe3 can be good candidates for thermoelectric materials, having narrow band gaps of 0.169 eV and 0.21 eV, respectively. All of the compounds are soft and brittle according to the second-order elastic constant calculations. Low Debye temperatures also support the softness. We have obtained the transport properties of the compounds by using rigid band and constant relaxation time approximations in the context of Boltzmann transport theory. The results show that the compounds could be considered for room temperature thermoelectric applications ( ZT ∼ 0.9 ).

WOS: 000311503000024, By means of plane-wave density functional first-principles calculations within the generalized gradient approximation (GGA), we report the structural, elastic and mechanical properties of MB12 (M = Zr, Hf, Y, Lu) with UB12-type structure. The lattice constants, bulk modulus, elastic constants and related quantities such as Young's modulus, shear modulus, Zener anisotropy factor, Poisson's ratio and Cauchy pressure are calculated and compared with the available experimental and other theoretical data. A deeper understanding, the pressure variations of the lattice constants, bulk modulus, elastic constants and other mechanical properties are also analyzed in a wide pressure range (0-50 GPa) and their trends are discussed. Additionally, Mulliken population analysis is used to clarify the bonding nature of all compounds. Combining the bonding nature and the structural information, microhardnesses of all compounds are calculated theoretically and then the detailed comparisons between hardness and other mechanical properties such as bulk modulus and shear modulus are made. (C) 2012 Elsevier B.V. All rights reserved., Turkish Prime Ministry State Planning Agency [2011K120290], This work was supported by the Turkish Prime Ministry State Planning Agency under Projects No. 2011K120290.

WOS: 000378873900059, We have performed first-principles density functional theory calculations within generalized-gradient approximation to obtain the structural, mechanical, electronic, and dynamic properties of Tin+1GaNn compounds. In order to examine the stability of these compounds, formation enthalpies, single-crystal elastic constants, and phonon dispersion curves were calculated. We show that all compounds are stable, while alpha-Ti4GaN3 is the most stable. The density of states calculations also demonstrate that all of the compounds are metallic. Additionally, bonding nature and related characteristics such as Mulliken atomic charges and bond overlap populations were investigated. Furthermore, thermodynamic properties were calculated by means of phonon dispersion curves. The results are compared in this work with available experimental values and theoretical calculations., State Planning Organization of Turkey [2011K120290], This work was partly supported by the State Planning Organization of Turkey under Grant No. 2011K120290. Some of the calculations were performed in the high performance computing center (HPCC) at Gazi University.

WOS: 000380852000080, The structural, mechanical and lattice dynamical properties of Ru2B3 and Os2B3 have been investigated by using a first-principles method based on the density functional theory within the generalized gradient approximation. The single crystal elastic constants are numerically estimated using strain-stress approach. The polycrystalline aggregate elastic parameters are calculated from the single elastic constants via the Voigt-Reuss-Hill approximations. Subsequently, the ductility and brittleness are characterized with the estimation from Pugh's rule (B/G) and Cauchy pressure. Additionally, the Debye temperature is calculated from the average elastic wave velocity obtained from bulk and shear moduli. The calculated parameters are consistent with the previous experimental and theoretical data. These borides are both mechanically and dynamically stable in the considered structure.

WOS: 000377049700011, Electronic structure and optical properties of the CdXO3 and ZnXO3 (XGe, Sn) compounds have been investigated based on density functional theory. According to the predictive results, reveal that the CdXO3 and ZnXO3 would be candidates for a high performance lead free optical crystal, which will avoid the environmental toxicity problem of the lead-based materials., project DPT-HAMIT; project DPT-FOTON; project NATO-SET [193]; project TUBITAK [113E331, 109A015, 109E301]; Turkish Academy of Sciences, This work is supported by the projects DPT-HAMIT, DPT-FOTON, NATO-SET-193 and TUBITAK under Project Nos., 113E331, 109A015, 109E301. One of the authors (Ekmel Ozbay) also acknowledges partial support from the Turkish Academy of Sciences. The numerical calculations reported in this paper were fully performed at Aksaray University, Science and Technology Application and Research Center.

WOS: 000301032100016, Based on density functional theory, we have studied the structural stability, elastic, mechanical, and lattice dynamical properties of BeB2, NaB2, and CaB2 compounds in AlB2, OsB2, and ReB2 structures, respectively. Generalized gradient approximation has been used for modeling exchange-correlation effects. Our calculations indicate that ReB2, AlB2, and OsB2 structures are energetically the most stable for BeB2, NaB2, and CaB2 compounds, respectively. The results show that these structures are both mechanically and dynamically stable. The bulk modulus, elastic constants, shear modulus, Young's modulus, Poisson's ratio, Debye temperature, sound velocities, and anisotropic factors are also calculated and discussed. Furthermore, the phonon dispersion curves and corresponding phonon density of states are presented. Our structural and some other results are in agreement with the available experimental and theoretical data. (C) 2011 Elsevier Ltd. All rights reserved.

WOS: 000301694500018, We have predicted structural, electronic, elastic, thermodynamic and vibration characteristics of TbN, using density functional theory within generalized-gradient (GGA) apraximation. For the total energy calculation we have used the projected augmented plane-wave (PAW) implementation of the Vienna Ab initio Simulation Package (VASP). We have used to examine structure parameter in eight different structures such as in NaCl (B1), CsCl (B2), ZB (B3), Tetragonal (L1(0)), WC (Bh), NiAs (B8), PbO (B10) and Wurtzite (B4). We have performed the thermodynamics properties for TbN by using quasi-harmonic Debye model. We have, also, predicted the temperature and pressure variation of the volume, bulk modulus, thermal expansion coefficient, heat capacities and Debye temperatures in a wide pressure (0-130 GPa) and temperature ranges (0-2000 K). Furthermore, the band structure, phonon dispersion curves and corresponding density of states are computed. Our results are compared to other theoretical and experimental works, and excellent agreement is obtained., Gazi University [05/2010-35], This work is supported by Gazi University Research - Project unit Project No: 05/2010-35.

WOS: 000300596000006, The structural, phase transition, elastic, lattice dynamic and thermodynamic properties of rare-earth compounds PrP and PrAs with NaCl (B1), CsCl (B2), ZB (B3), WC (B-h) and CuAu (L1(0)) structures are investigated using the first principles calculations within the generalized gradient approximation (GGA). For the total-energy calculation, we have used the projected augmented plane-wave (PAW) implementation of the Vienna Ab-initio Simulation Package (VASP). Specifically, some basic physical parameters, e.g. lattice constants, bulk modulus, elastic constants, shear modulus, Young's modulus and Poison's ratio, are predicted. The obtained equilibrium structure parameters are in excellent agreement with the experimental and theoretical data. The temperature and pressure variations of the volume, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature are calculated in wide pressure and temperature ranges. The phonon dispersion curves and corresponding one-phonon density of states (DOS) for both compounds are also computed in the NaCl (B1) structure. (C) 2011 Elsevier B.V. All rights reserved., Gazi University Research-Project Unit [05/2010-51], This work is supported by Gazi University Research-Project Unit under Project no: 05/2010-51.

WOS: 000296214300010, In this work, density functional theory calculations on the structural, mechanical, and lattice dynamical properties of AgB2 and AuB2 compounds in AlB2, OsB2, and ReB2 structures are reported. Generalized gradient approximation has been used for modeling exchange-correlation effects. The detailed information is given for the energetically most stable structure for AgB2 and AuB2 compounds. Specifically, the lattice parameters, bulk modulus, cohesive energies, elastic constants, shear modulus, Young's modulus, Poison's ratio, Debye temperature, sound velocities, and anisotropic factors are studied. The elastic properties are also studied under pressure. The phonon dispersion curves and corresponding phonon density of states are calculated and discussed. Our structural and some other results are in agreement with the available experimental and theoretical data. (C) 2011 Elsevier B.V. All rights reserved.

WOS: 000292725700001, The structural, mechanical, electronic and optical properties of orthorhombic PtSi and PtGe were investigated using norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory. The calculated lattice parameters and bulk modulus for PtSi and PtGe have been compared with the experimental and theoretical values. The second-order elastic constants were calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities and Debye temperature have also been estimated. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valance electrons and the effective optical dielectric constant were calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data.

WOS: 000290650200002, The plane-wave pseudopotential approach to the density-functional theory within the GGA approximation implemented in Vienna Ab-initio Simulation Package (VASP) code have been used to calculate structural, elastic and lattice dynamical properties of praseodymium chalcogenides: PrS, PrSe and PrTe. The structural properties are performed in five different crystal structures: NaCl (space group Fm3m(225)), CsCl (space group Pm3m(221)), ZB (space group F43m(216)), WC (space group P6m2(187)) and CuAu (P4/mmm(123)). Our results showed that these chalcogenides are stable in NaCl phase which are in agreement with the experimental works. The phonon dispersion curves are showed that the gap between the optic and acoustic branches decreases on going from PrS to PrTe. We have also estimated some thermodynamical properties such as entropy and heat capacity at the temperature range 0-1000 K. (C) 2011 Elsevier B.V. All rights reserved.

WOS: 000282453500010, First principles calculations are performed to investigate the structural, electronic, elastic, and thermodynamic properties of the less known PrN compound for various space groups: NaCl(Fm3m(2 2 5)), C5Cl(Pm3m (2 2 1)), ZB(F43m(2 1 6)), Wc(P6m2(1 8 7)), and CuAu (P4/mmm (1 2 3)). Our calculation indicates that the NaCl type structure is energetically more stable than the other phases. The calculated lattice parameters are consisted with available theoretical and experimental results. Our band structure calculations show that PrN possessess a semi-metallic character for both with and without spin polarized (SP) cases. The calculated elastic constants satisfy the mechanical stability conditions at all considered pressures and the present values are significantly higher than those of the previous results. The related mechanical properties such as Zener anisotropy factor (A), Poisson's ratio (v), Young's modulus (E), and shear modulus (C) are also computed for NaCl structure. The temperature/pressure-dependent behaviours of bulk modulus, Debye temperature, heat capacity, thermal expansion coeffient, and V/V-0 ratio estimated within the quasi-harmonic Debye model., Gazi University [05/2009-16], This work was supported by the Gazi University Research-Project Unit under Project no. 05/2009-16.

WOS: 000286112900018, The structural, elastic, electronic and optical properties of Zn1-xMgxSe ternary mixed crystals are investigated by utilizing the first-principles plane-wave pseudopotential method within the LDA approximations. Some basic physical properties, such as lattice constant, bulk modulus, second-order elastic constants (C-ij), Shear modulus, Young's modulus, Poison's ratio, Lame constants and the electronic band structures, are calculated. We have, also, predicted the optical properties such as dielectric functions, refractive index and energy loss function of these ternary mixed crystals. Our results agree well with the available data in the literature., Gazi University [05/2008-42], This work is supported by Gazi University Research-Project Unit under Project No: 05/2008-42.

We have investigated the structural, electronic, and optical properties of Zn1−xCaxSe ternary alloys using first principles calculations within the plane-wave pseudopotential method. Some basic physical properties, such as lattice constant, bulk modulus, electronic band structures, and optical properties (dielectric functions, refractive index, and energy loss function) were calculated. In addition, the effects of composition x on bulk modulus, band gap, refractive index and dielectric function were calculated. Our results agree well with the available data in the literature.

The structural, electronic and optical properties of CdxZn1-xS alloys have been studied using the first-principles plane-wave pseudopotential (PP) method within the local-density approximations (LDAs). The effects of composition on lattice constants, bulk modulus, band gap, dielectric functions, refractive index, extinction coefficient and energy loss function are investigated. It has been found that the lattice constants and bulk modulus change as almost linear for these alloys. Calculated electronic structure and density of states (DOS) of CdxZn1-xS alloys are discussed in terms of the contribution of Zn d, Cd d and p and S s and p states. Our results agree well with the available data in the literature. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

WOS: 000274222000019, A detailed theoretical study of structural, electronic, elastic, phonon, and thermodynamical properties of SmX (X = P, Sb, Bi) compounds is presented by performing ab-initio calculations based on density-functional theory using the Vienna ab-initio simulation package (VASP). For describing the interaction between electrons and ions, the projector-augmented wave (PAW) method is used. The generalized-gradient approximation (GGA) is chosen for the exchange-correlation functional. The calculated structural parameters, such as the lattice constant with and without spin-polarization (SP), bulk modulus, cohesive energy, second-order elastic constants, the electronic band structures and the related total density of states with and without SP and spin-orbit coupling (SOC) are presented. The high-pressure phase of all compounds is investigated and phase transition pressure from NaCl (B1) to high-pressure phase is determined. For B1 structure, the calculated values of lattice constants are compared with the available experimental and other theoretical data and bulk modulus values are compared with available other theoretical results. In order to gain further information, we have calculated Zener anisotropy factor (A), Poisson's ratio (nu), Young's modulus (E), shear modulus (C), elastic wave velocities, Debye temperature, phonon frequencies and one-phonon density of states for B1 structure of these three compounds. The temperature dependent behavior of heat capacity and entropy for these compounds in B1 phase is also presented. (C) 2009 Elsevier B.V. All rights reserved., Gazi University [05/2008-16], This work is supported by Gazi University Research-Project Unit under Project No: 05/2008-16.

We have investigated the structural and lattice dynamical properties of XB2(X=Sc,V,Ti) by using first-principles total energy calculations. Specifically, the lattice parameters (a, c) of the stable phase, the bond lengths of X–B and B–B atoms, phonon dispersion curves and the corresponding density of states, and some thermodynamical quantities such as internal energy, entropy, heat capacity, and their temperature-dependent behaviours, are presented. The obtained results for structural parameters are in good agreement with the available experimental and other theoretical studies.

WOS: 000266245900002, We have studied structural, elastic, thermodynamic (Debye temperature and melting temperature), and lattice dynamical (phonon dispersion curves, heat capacity, and entropy) properties of CaX via ab initio calculations within the local density approximations. The results are compared with the available experimental and other theoretical data, and the agreement is, generally, quite good. We also predict the temperature and/or pressure-dependent behaviors of some mechanical, lattice dynamical, and thermodynamic properties for the same compounds., Gazi University [05/2008-16], This work was supported by the Gazi University Research Project Unit under Project No: 05/2008-16.

Deligöz, Engin ( Aksaray, Yazar ), We have studied structural, thermodynamic, elastic, and electronic properties of cubic IrO2 polymorph via ab initio calculations within the LDA and GGA approximations. Basic physical properties, such as lattice constant, bulk modulus, second-order elastic constants (Cij), and the electronic band structures are calculated, and compared with available experimental values. We have, also, predicted the Young's modulus, Poison's ratio (ν), Anisotropy factor (A), sound velocities, and Debye temperature.

We have studied the structural, thermodynamics, elastic, and electronic properties of boron bismuth (BBi) compound in zinc-blende and rock-salt structures by performing ab initio calculations within the local density approximation. For the first time, we have calculated Debye temperature, melting temperature, phase transition pressure, phonon dispersion curves, density of state, and pressure dependences of the second-order elastic constants (C-ij) for this hypothetical compound. Calculations on the other basic key properties, such as the lattice constant, bulk modulus, and some band structural parameters are also repeated and compared with the other recent theoretical works. (C) 2006 Elsevier B.V. All rights reserved.

We present the results of our calculations on Boron antimony (BSb) compound in zinc-blende (ZB) and rock-salt (RS) structures by performing ab initio calculations within the local density approximation (LDA). Some basic physical properties, such as lattice constant, bulk modulus, cohesive energy, phase transition pressure, second-order elastic constants (C-ij), phonon frequencies, and some band structural parameters are calculated and compared with those obtained with other recent theoretical works. In order to further understand the behaviour of BSb compound, we have also predicted, the pressure-dependent behaviours of the band gap, second-order elastic constants (C-ij), Young's modulus, poison ratios (v), Anizotropy factor (A), sound velocities, and Debye temperature for this hypothetical compound. (C) 2007 Elsevier Ltd. All rights reserved.

The brief results of the first-principles ground-state total energy calculations for aliminium nitrat(AlN) in zincblende and rocksalt structures are presented. Structural, elastic, and electronic calculations are performed using the SIESTA method with norm-conserving pseudopotentials. The obtained results are compared with the available experimental and other theoretical data, and the agreement is, generally, quite good. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

WOS: 000364132300004, Using the generalized-gradient approximation (GGA) based on density functional theory, we have reported the structural, mechanical, electronic, and lattice dynamical properties of the intermetallic compounds Pd3X (X = Ti, Zr, Hf) with D0(24) and the L1(2) structures. The elastic constants were predicted using the stress-finite strain technique. We performed numerical estimations of the bulk modulus, shear modulus, Young's modulus, Poisson's ratio anisotropy factor, G/B ratio, and hardness. Our studies have showed that all Pd3X (X = Ti, Zr, Hf) with D0(24) and the L1(2) structures are mechanically stable and relatively hard materials with low compressibility, and they could be considered as ductile systems. Also, the phonon dispersion curves and total and partial density of states were calculated and discussed for Pd3X (X = Ti, Zr, Hf). We finally estimated some thermodynamic properties such as entropy, free energy, and heat capacity at the temperature range 0-1000 K. The calculated phonon frequencies of Pd3X (X = Ti, Zr, Hf) are positive, indicating the dynamical stability of the studied compounds. For the first time, we have performed the numerical estimation of lattice dynamical properties for the compounds and still awaits experimental confirmation. The obtained ground state properties are in good agreement with those of experimental and theoretical studies.

WOS: 000358148500004, The first-principles calculations are employed to provide a fundamental understanding of the structural features and relative thermodynamical, mechanical and phonon stability of TiAsTe compound. The calculated lattice parameters are in good agreement with available experimental results. We have computed elastic constants, its derived moduli and ratios that characterize mechanical properties for the first time. The calculated elastic constants indicate that these materials are mechanically stable at ambient condition. The minimum thermal conductivities of TiAsTe are calculated using both Clarke's model and Cahill's model. Furthermore, the elastic anisotropy has been visualized in detail by plotting the directional dependence of compressibility, Young's modulus and shear modulus. Our results suggest strong elastic anisotropy for this compound. Additionally, the phonon spectra and phonon density of states are also obtained and discussed. The full phonon dispersion calculations confirm the dynamic stability of TiAsTe.

WOS: 000349310200030, First-principles calculations are used to investigate the structural, elastic and vibration properties of the binary intermetallic compounds AgRE (RE = Ho, Er, Tm) with a B2 (CsCl) structure using density functional theory. The calculated structural parameters, the bulk modulus and its derivative with respect to pressure are in good agreement with experimental and numerical data. Additionally, the negative energy of formation of AgRE (RE = Ho, Er, Tm) with a B2 structure is examined. The independent second order elastic constants and their related properties, which are essential for mechanical stability, are investigated under pressure (0-60 GPa). The phonon spectra and phonon density of states are also discussed. All calculated phonon modes for AgRE (RE = Ho, Er) are positive in the phonon dispersion diagrams., Gazi University Research-Project Unit [05/2010-51]; Ankara University Research-Project Unit [12B4343020], This work was supported by Gazi University Research-Project Unit under Project No. 05/2010-51 and by Ankara University Research-Project Unit under Project No. 12B4343020. The numerical calculations reported in this paper were performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure).

WOS: 000361774100016, In this study, sol-gel spin coating route was carried out to prepare Scandium doped ZnO thin films with different controlled percentage (1-7%). Particularly, it has been demonstrated, through original conjoint morphological-structural and optical investigations, that some interesting physical properties were induced. Indeed, X-ray diffraction (XRD) analysis shows that (002) preferential crystalline plane for Sc doped ZnO films was kept along with ZnO hexagonal wurtzite structure, although Sc doping seemed to cause a decrease in crystallinity. Except for 1 at% Sc doping ratio, optical band gap changes reversely with Urbach energy with a decrease in optical gap and a broadening of the absorption tail. Ab-initio calculations of lattice dynamical properties outlined additional strong hybridization between Sc and O atoms and show the stability of Scandium doped ZnO.

WOS: 000349449900015, The anisotropic elastic properties of XYSb (X = Ti, Zr, Hf; Y = Si, Ge) compounds have been investigated by using first-principles calculations based on density functional theory. The calculated lattice parameters are in excellent agreement with the available experimental data. The computed elastic constants indicate that all compounds are mechanically stable according to the elastic stability criteria under pressure. We have calculated the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Debye temperature, and anisotropy value from the obtained elastic constants according to the Voigt-Reuss-Hill approximation. Additionally, the ductility and brittleness are characterized with the estimation from Pugh's rule (B/G) and Poisson's ratio. Furthermore, the elastic anisotropy have been visualized in detail by plotting the directional dependence of compressibility, Young's and shear moduli. (C) 2015 Elsevier Masson SAS. All rights reserved., Aksaray University Research [2013-58], This work is supported by Aksaray University Research- Project unit under Project No: 2013-58. The numerical calculations reported here were partially performed at Aksaray University, Science and Technology Application and Research Center.