Gokay Ugur

Gazi University · Department of Physics

Materials displaying anomalous quantum confinement effects (aqce) comprise the significant materials for recent optoelectronics, two-dimensional (2D) heterojunctions and band-gap engineering. Although available literature involves numerous works for regular 2D materials, there is still a lack of the key physical properties of aqce materials. So, in...

Density functional theory (DFT) calculations were conducted for the electronic and optical properties of the bulk, unstrained and strained monolayers of SrS2. Electronic band structures of the bulk SrS2 indicated an indirect bandgap with 1.32 eV, whereas the SrS2 monolayer displayed a higher indirect bandgap with 1.95 eV. Biaxial tensile strains of...

Our calculations allowing to establish a link between atomic topology and properties, based on the interpretation of the electronic structure. ScXCo2Sb2 (X = V, Nb and Ta) double half-Heusler alloys (DHH) are nonmagnetic materials. Based on an ab initio study these materials is found to be semiconductors with an indirect band gap in the range 0.56–...

We reported for the first time a theoretical study of structural, electronic, optical, elastic and thermodynamic properties of Ca4SiN4 and Ca4GeN4, based on DFT + PP-PW approach. The calculated structural parameters are in good agreement with the experimental data. Both considered alkaline earth metalloid nitrides are more compressible along the c-...

A density functional theory-based calculation of the magnetic structure, mechanical stability, electronic, and optical properties of quaternary Heusler alloys (QHAs) such as ZrCoFeX (X = Si, Ge) has been conducted. The most stable structure has been found among the various crystal arrangements of the alloys. Half-metallic ferromagnetism was obtaine...

In this work, structural, elastic and mechanical properties of Hf-doped TiAl2 and α-TiAl3 alloys up to 4 wt. % in increments of 0.5 wt. % have been investigated by first-principle calculations within density functional theory for the first time. The structural models have been established using the virtual crystal approximation (VCA) method. Theore...

Analyses based on first-principles simulations have revealed new details about the mechanical and thermodynamic characteristics of NaBH4 and NaAlH4 complex hydrides in α, β and γ phases. Using the quasi-harmonic Debye model, thermal parameters like the Debye temperature, the heat capacity, and the thermal expansion coefficient of NaXH4 (X = B, Al)...

The main objective of this work is to highlight several physical behaviors of two new compounds (MgS2 and MgSe2) in the cubic structure of the Pa-3 space group, particularly their mechanical and dynamical stabilities, their electronic behaviors and to provide a detailed analysis of bonding between the different atoms and the identification of weak...

Zr-Ti-X ternary alloys are striking materials of the latest technology because of their excellent and desired mechanical aspects. Therefore, electronic, elastic, mechanical and anisotropic properties of ZrTiX4 (X=Cr, Mo, W) alloys were probed in this work for the first time via density functional theory (DFT) calculations. The computed electronic b...

The thallium substitution effect on structural, electronic, and optical properties of chalcopyrite-type material AgGaS2 is investigated via first-principles approaches. The computed band gap energy of pure AgGaS2 is about 2.59 eV using Tran-Blaha (TB)-modified Becke Johnson (mBJ) exchange potential, which is in good accord with experimental measure...

Titanium-based alloys are still fascinating materials of today's technology with prevalent use in aviation, biomaterial and automobile industries because of their superior mechanical properties. Further, Ti-5Al-XSn alloys can be defined as the second popular grades after the pioneer Ti-6Al-4V (Ti64) grades. Although it is possible to find many expe...

First-principles calculations were carried out for the electronic, elastic, mechanical and anisotropic behavior of W3XC2 (X: Si, Ge and Al) alloys. Electronic bands analyses reveal an obvious metallic character for all of the investigated alloys. In addition, the calculated magnitudes of Young's modulus of the alloys follow the range of W3SiC2> W3A...

DyOs4P12 is a ferromagnetic metal that has a very low Curie temperature of about 2 K. This work will offer a wide-ranging theoretical study complementary to experimental work on this compound. The found results have confirmed the mechanical stability of DyOs4P12 under slight mechanical strains and the elastic anisotropy analysis has shown that it i...

We report the structural, elastic, mechanical and electronic properties of nitrogen (N)-doped cubic diamond up to 25%N doping concentrations in the steps of 5%N dopant. Our calculations were performed with the generalized gradient approximation functional of density functional theory with the Perdew–Burke–Ernzerhof exchange–correlation energy throu...

We theoretically investigated the structural, elastic and mechanical properties of Ti–15Nb–xGe alloys with x = 0.8, 1, 1.2, 1.4, 1.6 and 1.8 (wt%) compositions for the first time. Theoretical calculations were performed with the generalized gradient approximation (GGA) functional within density functional theory (DFT). We employed the Perdew–Burke–...

First-principles density functional theory (DFT) study calculations were performed for various elastic and mechanical properties of Ti64, Ti6242 and Ti6246 alloys. Generalized gradient approximation and the Perdew–Burke–Ernzerhof scheme of DFT were employed to present calculations together with virtual crystal approximation. All of the investigated...

We report some unclarified physical properties of Ce3XY (X = Al, In and Y = C, N) inverse cubic perovskites by conducting a density functional theory (DFT) study. The elastic, mechanical, magnetic, thermodynamic and optical properties of these compounds were addressed. Obtained elastic data prove the mechanical stability, elastic anisotropy and bri...

We performed density functional theory (DFT) calculations to explore the electronic, optical, elastic and thermoelectric properties of Nb2WNi alloy for the first time by addressing the two different crystal structures (Cu2MnAl and Hg2CuTi) of the alloy. The calculated elastic constants results prove the mechanical stability for both crystal structu...

We have addressed the several unpublished elastic, mechanical, optical, anisotropic and magnetic properties of V2NiSb inverse Heusler alloy through the density functional theory (DFT) framework. Calculated elastic constants indicate mechanical stability and ductile mechanical character of the alloy. The alloy has high elastic anisotropy. Some optic...

We report the electronic, elastic, mechanical, optical, and magnetic properties of Rh2MnX (X = Ti, Hf, Sc, Zr, Zn) Heusler alloys performed within density functional theory. The generalized gradient approximation was used for calculations in the context of the Perdew–Burke–Ernzerhof exchange‐correlation energy treatment. The computed elastic consta...

We have theoretically investigated the elastic, mechanical, optical and magnetic properties of Ru2MnX (X = Nb, Ta, V) Heusler alloys within density functional theory (DFT). The generalized gradient approximation (GGA) was employed to research with Perdew-Burke-Ernzerhof (PBE) exchange-correlation energy. Obtained elastic constants and elastic modul...

We report the electronic, elastic, mechanical, optical and magnetic properties of Rh2MnX (X=Ti, Hf, Sc, Zr, Zn) Heusler alloys performed within density functional theory (DFT). The generalized gradient approximation (GGA) was used for calculations in the context of the Perdew-Burke-Ernzerhof (PBE) exchange-correlation energy treatment. The computed...

We report the structural, elastic, electronic, optical and vibrational properties of double half Heusler (DHH) compounds Ti2FeNiSb2 and Ti2Ni2InSb within density functional theory (DFT) for the first time. The calculated elastic constants express that both compounds are mechanically stable and show ductile mechanical character. Computed band struct...

Several magnetic, electronic and elastic behaviors of HoFe4P12 filled-skutterudite remain unknown, therefore, this study is complementary to the experimental works carried out on this compound. Experimental results have shown that HoFe4P12 shows a ferromagnetic transition at around 5 K, therefore, the ground state properties studied in this work ha...

Ab initio predictions for strontium chalcogenides such as SrS, SrSe, and SrTe doped with magnetic titanium (Ti) element as the Sr1 − xTixX (X = S, Se, and Te) diluted magnetic semiconductor (DMS) compounds in rock-salt ferromagnetic structure have been studied at concentration x = 0.25, by using the full-potential linearized augmented plane wave pl...

Cation disorder in cobalt ferrite spinels have significant effects on its electronic, magnetic and optic behavior. The cations inversion effect between tetrahedral (Td) and the octahedral (Oh) positions on electronic and magnetism in Co1−yFey(CoyFe2−y)O4 with 0 ≤ y ≤ 1 cobalt ferrites is reported. It is found that cobalt ferrites exhibit strong fer...

Weak interactions are not negligible in layered structures and contribute strongly in their physical behaviors. Thanks to NL-vdW functionals and analysis methods of the electron density, their analysis is possible, which allows to better understand their effects on the different physical properties of solids. We have studied the role of weak intera...

We report the structural, elastic, mechanical, electronic and optical properties of Ba2K2Te2O9 (dibarium dipotassium nonaoxidoditellurate) triple perovskite compound by employing generalized gradient approximation (GGA) of first principles density functional theory (DFT) within Perdew-Burke-Ernzerhof (PBE) exchange correlation energy for the first...

Although numerous theoretical studies are available for the band gap energies of distinct silica (SiO2) polymorphs, some of the calculated results of these former studies still remain inconsistent and mostly disagree with the experimental data of the investigated polymorphs. To obtain more reasonable results, we have focused on the band gap energie...

Using PP-APW method the electronic, optical and mechanical anisotropy of ZnRE2S4 (RE = Er, Tm) olivine compounds was investigated. The calculated unit cell parameters are in good agreement compared to the experimental ones. In addition, the study of electronic properties reveals that ZnEr2S4 and ZnTm2S4 are semiconductors with a direct bandgap of a...

A DFT study of homonuclear X 2 ([Formula: see text], As, Se, Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn) is presented using PBEO exchange (xc) functional which is a mixing of Perdew–Burke–Ernzerhof (PBE) and Hartree Fock (HF) exchange energy. However, we used cc-pVXZ and aug-cc-pVXZ basis sets where X is maximum angular momentum number in basis set. Converg...

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]PN 2 (X = Li, Na) chalcopyrite such as structural, electronic, elastic and thermoelectric pro...

We performed first principles calculations to determine the typical cubic elastic constants (C11, C12 and C44), bulk modulus (B), shear modulus (G) and Young’s modulus (E) of TlBr and TlCl compounds. We employed two different GGA functionals, the Perdew-Wang 1991 (PW91) and the Perdew-Burke-Ernzerhof (PBE) for the exchange and correlation energy to...

Several previous works have shown that (Lenaite) AgFeS2 has a chalcopyrite structure with I-42d space group, but several information about its magnetic and optoelectronic behavior remain still unknown. The study of these properties is the main objective of our work, which is based on several theoretical approaches. The determination of the most sta...

First principles calculations have been used to investigate the structural phase transitions and lattice dynamics in the alloy Lix Na1-xMgH3. The density functional perturbation theory (DFPT) and the virtual crystal approximation (VCA) are employed, within the generalized gradient approximation. Our total energy and formation energy results show th...

In this study, an eleven-parameter rigid-ion model (RIM) is proposed for BaFX (X = Cl, Br and I) matlockite structure compounds. The interatomic interactions up to fourth nearest neighbors for the studied compounds are calculated. The zone-center raman and infrared phonon mode frequencies, elastic constants, bulk modulus B, shear modulus G, Young’s...

In the present study ab initio methology under density functional theory with generalized gradient approximation is used to study the structural, elastic, and vibrational properties of TiMg2O4 with cubic and tetragonal phases with space groups (Fd\( \overline{3} \)m) and P4_122, respectively. The present study shows that the studied compound TiMg2O...

Structural, elastic, electronic and vibrational properties of XAl2O4 (X = Ca, Sr and Cd) compounds with orthorhombic structure are studied by first principles method within generalized gradient approximation. The calculated negative formation enthalpy for each compounds indicates the thermodynamical stability of the studied phase. Band structure ca...

According to several previous works, Li2S2 occurs during discharge of lithium–sulfur (Li–S) batteries. Several information on the physical properties of this compound remain unknown including those of its ground state. In this work, a study of the pressure effect on the elastic and optoelectronic properties of Li2S2 in its tetragonal structure of P...

XLa2S4 (X = Ba; Ca) sulfides are widely used as materials for application in infrared region, but the theoretical studies on these materials are limited and incomplete. Using the augmented plane wave + local orbitals (APW + lo) method with different approximation functionals, we performed a systematic theoretical study on the structural, electronic...

A detailed theoretical investigation on the structural, elastic, electronic, thermoelectric, thermodynamic and optical properties of half-Heusler MRhSb (M = Ti, Zr, Hf) compounds is presented. The computations are carried out using the full potential linear augmented plane wave method (FP-LAPW) within density functional theory (DFT). The optimized...

The phase diagrams of Al-Ba and Ba-Ge systems are optimized by coupling the CALPHAD approach and first-principles calculations. The binary intermetallic compounds were treated as stoichiometric phases. The total energies of nine intermetallic compounds: Al4Ba, Al13Ba7, Al5Ba3, Al5Ba4, Ba2Ge, Ba5Ge3, BaGe, β-Ba3Ge4 and BaGe2 were calculated by first...

In the present paper we have investigated the electronic structure of some orthorhombic A3X2S7 (X = Ti, Zr, and Hf) compounds based on the density functional theory. Then we extend the Ruddlesden–Popper (RP) A3X2S7 sulfides and examine how ferroelectricity is induced by coupled octahedral rotation modes. The mechanical and optical properties have a...

The concentration dependence of the phase stability, half-metallicity, thermal and magnetic properties of Fe2MnxNi1−xSi (0 ≤ x ≤ 1) Heusler alloys in two structures, Cu2MnAl (Fm3m) and Hg2TiCu (F43m), were investigated at the ab initio level using density functional theory. The exchange–correlation term was assessed using local spin density (LSDA)...

Full potential band structure calculations have been performed on the NiAs (hexagonal), MnP (orthorhombic) and Zinc-blende structures of MnAs1−xPx (0 ≤ x ≤ 1) alloys. The stability of the ferromagnetic state is investigated by comparing the total energies for paramagnetic (P), ferromagnetic (F) and antiferromagnetic (AF) state, where different type...

First-principles density functional theory (DFT) calculations within generalized gradient approximation (GGA) are carried out to investigate the structural, electronic, mechanical, lattice dynamical and thermodynamic properties of Ti2AN (A = Si, Ge and Sn) MAX phases. The optimized geometrical parameters such as lattice constants (a, c) and the int...

We report the results of the FP-APW + lo calculations of the structural, electronic, optical and thermo-electric properties of the CdY2Ch4 (Ch = S, Se) compounds under hydrostatic pressure effect. The calculated ground state properties agree well with the available experimental data. The investigated materials are semiconductors, with direct band g...

We report results of ab-initio studies for the structural, electronic, lattice dynamical and electron-phonon interaction properties of cubic and tetragonal phases of V3Si by using the plane-wave pseudopotential method, the density-functional theory, and a linear-response technique. Our total energy results propose that the martensitic transition fr...

We have studied the structural, optical, electronic and thermoelectric properties of the CaCd2X2 (X = P, As) compounds by using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). The exchange-correlation potential was treated using both the gradient generalized approximation (WC-GGA) and local density approximation (L...

First-principles calculations were used to calculate the structural, electronic and half-metallic ferromagnetism of Mn2RuGe1-xSnx (x=0, 0.25, 0.50, 0.75, 1) Heusler alloys. The Hg2CuTi-type structure is found to be energetic more than Cu2MnAl-type structure for both Mn2RuGe and Mn2RuSn compounds. The calculated lattice constants for Mn2RuGe and Mn2...

First principles density functional theory calculations were performed to study structural, electronic, elastic, optical and vibrational properties of CoAl2O4 and MnAl2O4 aluminate spinels. Computed ground state properties such as unit-cell parameter and oxygen positional parameter differ by less than 1% from previously available theoretical and ex...

The phase diagrams of Yb-Cd and Yb-Sn systems were calculated by coupling the CALPHAD method and ab initio calculations. The enthalpies of formation of nine binary compounds (YbCd, αYbCd2, Yb2Sn, αYb5Sn3, βYb5Sn3, Yb5Sn4, YbSn, Yb3Sn5 and YbSn3) were determined via ab initio density functional theory using the VASP code. Based on the available expe...

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlati...

A comprehensive study of structure, phase stability, electronic, vibrational and thermodynamic properties of LiMgSb and LiZnSb compounds is performed by carrying out First-principles calculations within density–functional theory using the full potential linearized augmented plane wave (FP-LAPW) combined with the pseudo-potential method. The general...

Structural and elastic properties of silver chromate in normal (CrAg2O4) and inverse (Ag2CrO4) spinel structure have been studied using density functional theory (DFT) together with PerdeweBurke eErnzerhof (PBE) exchangeecorrelation functional implemented in VASP package. It is observed that studied compound satisfy the well-known requirements of m...

In present work, our research is mainly focused on the electronic structures, optical and magnetic properties of Cu2FeSnZ4 (Z = S, Se) compounds by using ab initio calculations within the generalized gradient approximation (GGA). The calculations are performed by using the Vienna ab-initio simulation package (VASP) based on the density functional t...

Using first-principles calculations based on density functional theory, the structural, electronic and thermodynamic properties of Li2CdGeS4 and Li2CdSnS4 compounds are investigated. We confirmed that both Li2CdGeS4 and Li2CdSnS4 are diamond-like semiconductors of the wurtz-stannite structure type based on that of diamond in terms of tetrahedra vol...

In this work, we have theoretically investigated the band structure of antiperovskite chromium-based carbides and nitrides Cr3PX (X = C and N) using the first-principles calculation based on the FP-APW+lo method. The principal structural properties i.e., lattice constants (a,b,c) and internal parameters are in accordance with the experimental resul...

Electronic band structure, optical and thermodynamic properties of ternary hydrides MBeH3 (M = Li, Na, and K) were studied using ab initio density functional theory (DFT). The effect of the adopted approximation to the exchange-correlation functional of the DFT is explicitly investigated by considering four different expressions of two different cl...

In this work, density functional theory plane-wave pseudo potential method, with local density approximation (LDA) and generalized gradient approximation (GGA) are used to investigate the structural, elastic, mechanical and thermodynamic properties of the intermetallic compound Mg3Rh. Comparison of the calculated equilibrium lattice constants and e...

A comprehensive study of structure, phase stability, optical and electronic properties of LiAlH4 and NaBH4 light-metal hydrides is presented. The calculations are carried out within density functional theory using the full potential linear augmented plane wave method. The exchangecorrelation potential is treated within the local density approximati...

The structural, electronic, elastic and phonon properties of the cubic spinels AB2O4 (A = Ge, Si; B = Mg, Zn, Cd) compounds at zero pressure are investigated via density functional theory (DFT) using the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional. It has been shown that the predicted values of the structural parameters (a0 and u),...

ab İnitio calculations have been performed to study the structural, electronic, elastic, mechanical, thermodynamical and phonon properties of LuS and LuTe with the generalized gradient approximation for exchange and correlation. The calculated lattice constants, bulk modulus, its pressure derivative and elastic constants are calculated. The calcula...

We have studied the structural, elastic, electronic, phonon and thermodynamic properties of Ir3Ta and Rh3Ta alloys, using ab initio calculations. For the L12 phase, we report the calculated lattice constants, bulk modulus and elastic constants, and these values are compared with previously published values. We also derive the elastic constants from...

We present ab initio calculations of the structural, electronic structures, elastic, thermodynamic and vibrational properties of the Ir 3 Hf compound in the L1 2 structure. The calculated lattice constants, bulk modulus, and first-order pressure derivative of the bulk modulus are reported for the L1 2 structure and compared with the earlier values....

We present ab initio calculations of the structural, electronic structures, elastic, thermodynamic and vibrational properties of the Ir 3 Hf compound in the L1 2 structure. The calculated lattice constants, bulk modulus, and first-order pressure derivative of the bulk modulus are reported for the L1 2 structure and compared with the earlier values....

A combined first-principles and thermodynamic study of the Bi-Cs and Bi-Tm systems has been performed and a self-consistent thermodynamic database has been obtained. The enthalpies of formation of Bi2Cs, Bi4Cs5, Bi2Cs3, BiCs3, BiTm and Bi3Tm5 are computed via density functional theory using the VASP code. The CALPHAD assessment of Bi-Cs and Bi-Tm s...

Pseudopotential plane-wave method based on density functional theory within the generalized gradient approximation for the exchange-correlation potential has been applied to study the structural, electronic, elastic and vibrational properties of the binary intermetallic Pd3V and Pt3V in the L12 phase. The optimized lattice constant, bulk modulus an...

First-principle calculations have been carried out on the structural, electronic, elastic, and phonon properties of the full-Heusler alloys X2YAl (X = Co, Fe and Y = Cr, Sc). The calculations predict that the Fe2CrAl and Co2CrAl are half-metallic ferromagnets at the equilibrium lattice constant with a minority-spin energy gap of 0.2912 and 0.668 eV...

In this paper, the structural, elastic and phonon properties of Ti3Al and Y3Al in L12(Cu3Al) phase are studied by performing first-principles calculations within the generalized gradient approximation. The calculated lattice constants, static bulk moduli, first-order pressure derivative of bulk moduli and elastic constants for both compounds are re...