An ab initio Study of Cr and Mn Doped MAX Phase TiMSiB

MAX phases, which are widely studied experimentally and theoretically, have general formula of M(n1)AXn, where M is transition metals, A is A group element and X is C and N. In this study, the structural, mechanical and electronic properties have been researched for hypothetical MAX phase TiMSiB, where M is Cr and Mn by applying ab initio calculations. Initially, structural optimizations have been completed and the outcomes crosschecked with the studies of Ti2SiB in literatures [1]. After optimization process have been achieved, the mechanical stability has been proved. Moreover, Young, Bulk, Shear modules and Poisson ratio for the compounds have been estimated by using elastic constants. Also, to understand the anisotropic behavior of the materials, directional dependent two and three-dimensional mechanical properties have been plotted. Finally, electronic band structures and corresponding density of state (DOS) have been plotted. © 2019 IEEE

The investigation of electronic, anisotropic elastic and lattice dynamical properties of MAB phase nanolaminated ternary borides: M2AlB2 (M ¼ Mn, Fe and Co) under spin effects

In the present study, the structural, electronic, magnetic, anisotropic elastic and lattice dynamic properties of the ternary metal borides M2AlB2 (M=Mn, Fe and Co) known as MAB phases have been investigated by density functional theory. The obtained results from the structural optimizations show that all these compounds have negative formation enthalpy implying the thermodynamic stability and synthesizability. The spin effects on the M2AlB2 phases have been studied with the plotted energy-volume curves for different magnetic phases (antiferromagnetic (AFM), ferromagnetic (FM), and paramagnetic (PM)) of these compounds. The stable magnetic phase for the Mn2AlB2 compound is found to be AFM while the magnetic nature of Fe2AlB2 and Co2AlB2 compounds are FM. The calculated electronic band structures with the total and orbital projected partial density of electronic states imply that these ternary metal borides have metallic behavior. Also, the mentioned compounds have mechanical and dynamic stability due to the calculated elastic constants and the observed phonon dispersion curves. Some thermodynamic properties have been investigated by means of phonon dispersion curves. Furthermore, the anisotropic elastic properties have been visualized in three dimensions (3D) for Young's modulus, linear compressibility, shear modulus, Poisson's ratio, and sound wave velocities. © 2020 Elsevier B.V

THE INVESTIGATION OF THE ELECTRONIC AND VIBRATIONAL PROPERTIES OF SOME COMPOUNDS WITHIN THE DENSITY FUNCTIONAL THEORY

Yoğunluk Fonksiyonel Teorisi ve ab-initio pseudo potansiyel metodu ile LaAs ve LaP bileşikleri için NaCl ve CsCl yapıda, LaN ve LaSb bileşikleri için de sadece NaCl yapıda Genelleştirilmiş Gradient Yaklaşımı (GGY) kullanılarak yapısal, elektronik ve titreşimsel özellikleri araştırıldı. Bu altı bileşik için hesaplanan örgü sabiti değerlerinin, mevcut deneysel ve diğer teorik sonuçlarla uyumlu olduğu gözlendi. Hesaplanan örgü sabitleri ve bant yapısı kullanılarak Yoğunluk Fonksiyonel Pertürbasyon Teorisi üzerine kurulu lineer tepki yaklaşımında fonon frekansları hesaplandı. LaSb bileşiğinin de hesaplanan fonon spektrumunun mevcut deneysel değerlerle uyum içerisinde olduğu görüldü. LaAs ve LaP bileşiklerinin CsCl yapısında ve LaN bileşiğinin NaCl yapısında hesaplanan fonon frekansları kararsız çıktı. izmir gundem komik videolar cizgi film izle cizgi film 3d oyunlar oyunlar We have investigated the structural, electronic and vibrational properties of LaAs and LaP compounds in the NaCl structure and the CsCl structure, LaN and LaSb compounds only in the NaCl structure by using General Gradient Approximation (GGA) of the density functional theory and ab-initio pseudopotentials. The calculated lattice constants of these six compounds are in good agreement with the available experimental and other theoretical results. These lattice constants and calculated electronic band structures have been used in the application of a linear response approach based on density functional perturbation theory for phonon studies. The calculated phonon spectra of LaSb are also in good agreement with available experimental data. The calculated phonon frequencies of LaAs and LaP compounds in the CsCl structure and LaN compound in the NaCl structure are unstable

The investigation of the structural, mechanical, electronic and magnetic properties of some oxide crystals in ABO3 type perovskite structure within the density functional theory

YÖK Tez ID: 418457Kübik perovskite yapıdaki manyetik geçiş metal oksitlerinden PbMO3 (M=Fe, Co ve Ni) kompozit yapılarının yapısal, manyetik ve elektronik özellikleri hesaplanmıştır. Hesaplamalar Yoğunluk Fonksiyonel Teorisi altında düzlem dalga pseudo potansiyel metodu ile değiş tokuş-korelasyon fonksiyoneline Yerel Spin Yoğunluk Yaklaşımı (LSDA) kullanılarak yapılmıştır. Aynı zamanda hesaplamalara Coulomb etkileşimi de dahil edilmiştir (LSDA+U). Sistemler ferromanyetik (FM) ve G-tipi antiferromanyetik (G-AFM) olarak düşünülmüştür. Çalışılan tüm sistemlerin enerji değerlerine bakıldığında ferromanyetik yapıların G-tipi antiferromanyetik ve manyetik olmayan yapılara oranla daha kararlı olduğu gözlenmiştir. Spin polarize edilerek hesaplanan elektronik band yapıları göstermiştir ki, tüm yapılar, Hubbard-U etkileşimi (Uetkin=0) olmaksızın ferromanyetik fazda incelendiğinde metalik davranış göstermektedir. Fakat, Coulomb etkileşimi dahil edildiğinde (Uetkin=7 eV) PbFeO3 ve PbNiO3 bileşiklerinde yarı metalik davranışın bir sonucu olarak yukarı spin durumlarında band aralığı gözlenmiştir. PbCoO3 bileşiğinde ise LSDA+U metodu uygulanmasına rağmen yine metalik davranış gözlenmiştir. Tüm yapıların bağlanma özelliklerinin geçiş metal atomlarının d durumları ile O-p durumları arasında meydana gelen hibritleşme olduğu sonucuna varılmıştır. PbFeO3 bileşiği içerisindeki Fe atomunun kısmi manyetik moment değerinin, Hubbard-U etkileşimi ile arttığı görülmüştür. Ayrıca yarı metalik PbFeO3 ve PbNiO3 bileşiklerinin toplam manyetik momentlerinin tam değerlere çok yakın olduğu görülmektedir. Ferromanyetik tetragonal perovskit yapıdaki manyetik geçiş metal oksitlerinden PbMNbO3 (M=Fe, Co ve Ni) kompozit yapılarının yapısal, manyetik ve elektronik özellikleri hesaplanmıştır. Hesaplamalar Yoğunluk Fonksiyonel Teorisi altında düzlem dalga pseudo potansiyel metodu ile değiş tokuş-korelasyon fonksiyoneline Yerel Spin Yoğunluk Yaklaşımı (LSDA) uygulanarak yapılmıştır. Aynı zamanda hesaplamalara Coulomb etkileşimi de dahil edilmiştir (LSDA+U). Ayrıca söz konusu bileşiklerde manyetik M (M=Fe, Co ve Ni) atomlarının atomik konumlarının yeri [001] doğrultusunda küçük miktarlarda değiştirilerek yapıların yeni durumlarındaki enerji değerlerine bakılmıştır. Böylece, multiferroik olarak bilinen bu yapıların ferroelektrik özellikleri üzerine vurgu yapıldı. Ayrıca PbMNbO3 (M=Fe, Co ve Ni) kompozit yapılarının, spin polarize edilerek hesaplanan elektronik bant yapıları incelendiğinde, Hubbard-U etkileşimi (Uetkin=0) yokken ferromanyetik fazda metalik davranış gösterdikleri görülmüştür. Bunun yanında aynı bileşiklere Uetkin=7 eV olacak şekilde bir Hubbard potansiyeli uygulandığında ise PbNiNbO3 ve PbCoNbO3 bileşiklerinde metalik davranış gözlenmesine karşın PbFeNbO3 bileşiğinde yarı metalik davranışın bir sonucu olarak aşağı spin durumlarında bir bant aralığı gözlenmiştir. Bu yapıların bu tür davranışlar sergilemesinin nedeni geçiş metal atomlarının d durumları ile oksijen atomlarının p durumları arasında meydana gelen hibritleşmedir. ABO3 tipi perovskit oksitlerden LaMO3 (M=Ga, In ve Tl) bileşikleri, Genelleştirilmiş Gradient Yaklaşımı (GGA) kullanılarak Yoğunluk Fonksiyonel Teorisi (DFT) altında VASP (Vienna Ab Initio Simulation Package) paket programı [106-108] yardımı ile kübik (Pm-3m), tetragonal (P4mm), rombohedral (R3) ve ortorombik (Pbnm) fazlarda incelenerek hangi fazda kararlı oldukları tespit edildikten sonra faz geçiş basınçları hesaplanmıştır. Daha sonra kararlı oldukları ortorombik (Pbnm) fazda yapısal, mekanik ve elektronik özellikleri incelenmiştir. LaTlO3 bileşiği rombohedral (R3) fazda optimize edilemediğinden söz konusu bileşik için sadece üç fazda çalışılmıştır. Söz konusu bileşikler için yasak enerji aralıkları (Eg) sırası ile yaklaşık olarak 3.321 eV, 2.697 eV ve 1.098 eV olarak bulunmuş olup, enerji bant grafikleri ve toplam durum yoğunlukları yüksek simetri yönleri boyunca çizilmiştir.The structural, magnetic, and electronic properties of the magnetic transition metal oxides PbMO3 (M=Fe, Co and Ni) in cubic perovskite structure have been calculated. The calculations are based on the density functional theory (DFT) within plane-wave pseudopotential method and local spin density approximation (LSDA) of the exchange-correlation functional. On-site Coulomb interaction is also included in calculations (LSDA+U). The systems are considered in ferromagnetic (FM) and G-type antiferromagnetic (G-AFM) order. Ferromagnetic structures are energetically more favored than G-type antiferromagnetic and than non-magnetic states for all the systems studied. The spin-polarized electronic band structures show that all the structures have metallic property in ferromagnetic order without Hubbard-U interaction (Ueff = 0). However, the inclusion of on-site Coulomb interaction (Ueff = 7 eV) opens a semiconducting gap for majority spin channel of PbFeO3 and of PbNiO3 resulting in a half-metallic character. PbCoO3 system remains metallic with LSDA+U scheme. The bonding features of all structures are largely determined by the hybridizations between O–p and d-states of transition metal atoms. The partial magnetic moment of Fe atom in PbFeO3 is enhanced by inclusion of Hubbard-U interaction. Also, total magnetic moments of half-metallic PbFeO3 and of PbNiO3 compounds are very close to integer values. The structural, magnetic, and electronic properties of the magnetic transition metal oxides PbMNbO3 (M=Fe, Co and Ni) in ferromagnetic tetragonal perovskite structure have been calculated. The calculations are based on the density functional theory (DFT) within plane-wave pseudopotential method and local spin density approximation (LSDA) of the exchange-correlation functional. On-site Coulomb interaction is also included in calculations (LSDA+U). Besides, the energy changes have been calculated in these compounds by changing the position of M (M = Fe, Co and Ni) atom along [001] direction. Thus, the ferroelectric properties of these structures have been emphasized as multiferroic systems. The spin-polarized electronic band structures of PbMNbO3 (M =Fe, Co, and Ni) systems exhibit metallic property in ferromagnetic phase without Hubbard U interaction (Ueff = 0 eV). When a Hubbard potential as Ueff = 7 eV is applied to the same compounds, a band gap is observed in spin-down states of PbFeNbO3 resulting in half-metallic behavior, although PbNiNbO3 and PbCoNbO3 compounds remain metallic. The main reason of this behavior is the hybridization between d-states of transition metal atoms and p-states of oxygen atoms. Among the class of ABO3 type perovskite oxides, LaMO3 (M=Ga, In, and Tl) compounds have been investigated in cubic (Pm-3m), tetragonal (P4mm), rhombohedral (R3), and orthorhombic (Pbnm) phases by using Generalized Gradient Approximation (GGA) in the Density Functional Theory (DFT) as implemented in VASP (Vienna Ab Initio Simulation Package) software [106-108]. After the determination of the stable phase, phase transition pressures have also been calculated. Then, their structural, mechanical, and electronic properties have been studied in stable orthorhombic (Pbnm) phase. LaTlO3 compound has been studied in only three phases, since it cannot be optimized in rhombohedral (R3) phase. The energy gaps (Eg) of these compounds have been found as 3.321 eV, 2.697 eV and 1.098 eV, respectively. Their electronic band structures and total density of states have been drawn along the high symmetry directions

Bazı ABO3 tipi perovskite oksit kristallerin yapısal, mekanik, elektronik ve manyetik özelliklerinin yoğunluk fonksiyoneli teorisi ile incelenmesi

Tez (Doktora) -- Kırıkkale Üniversitesi100186

The effect of Sn doping on the electronic and mechanical properties of Ti3Al1-xSnxC2 MAX phases

WOS:000646072900004The phase pure synthesis of Ti3AlC2 MAX phase is quite difficult and some additives are required to get a phase pure Ti3AlC2 such as Sn. In this study, Sn doped Ti3AlC2 MAX phase has been investigated taking into account the experimental synthesis conditions where some Sn atoms could replace Al atoms in the structure. For this purpose, Ti3Al1-xSnxC2 with x ranging from 0 to 1 with 0.1 interval has been studied using the first principles method and the results show that all compositions are thermodynamically stable. The electronic properties of these compositions have been studied using band filling theory in detail. Also, the mechanical properties of these compounds such as shear modulus, Poisson's ratio, Young's modulus, sound wave velocities, polarization of the sound waves, enhancement factor, the power flow angle and etc. have been obtained with the varying directions and the three-dimensional mechanical properties have been visualized

Gümüş-Tabanlı Sülfürün Manyetik Doğası ve Elektronik Davranışı Üzerine İlk-İlkeler Çalışması: Ag3MnS4

This investigation is about the electronic and magnetic character of the ternary silver-based sulfide (Ag3MnS4) crystallized in sulvanite type crystal structure with space group P4 ̅3m and space number 215. The mentioned characteristics has been examined by Generalized Gradient Approximation (GGA) with spin effect under Density Functional Theory (DFT). Four different magnetic phases have been considered to investigate the proper magnetic order for this system. As a result of calculations, it has been understood that, for Ag3MnS4 compound, the energetically most favored magnetic order is A-type antiferromagnetic. After the well-optimized structural parameters and relaxed atomic positions in its suitable magnetic order have been obtained, the electronic characteristic of this antiferromagnet system indicating semiconducting behavior due to the observed a small direct band gap (Eg = 0.325 eV) in both spin states, has been investigated. Also, this compound has thermodynamic stability and structural synthesizability due to its calculated negative formation energy values for all different type magnetic phases.Bu araştırma, boşluk grubu P4 ̅3m ve boşluk sayısı 215 ile sülvanit tipi kristal yapısında kristalize olan üçlü gümüş bazlı sülfidin (Ag3MnS4) elektronik ve manyetik karakteri ile ilgilidir. Bahsedilen özellikler Yoğunluk Fonksiyonel Teorisi (YFT) altında spin etkisi ile Genelleştirilmiş Gradyan Yaklaşımı (GGY) ile incelenmiştir. Bu sistem için uygun manyetik düzeni araştırmak için dört farklı manyetik faz düşünülmüştür. Hesaplamaların bir sonucu olarak, Ag3MnS4 bileşiği için, enerjisel olarak en çok tercih edilen manyetik düzenin A-tipi antiferromanyetik olduğu anlaşılmıştır. İyi optimize edilmiş yapısal parametreler ve uygun manyetik düzendeki relax edilen atomik pozisyonlar elde edildikten sonra, her iki spin durumunda da küçük bir direkt bant boşluğunun (Eb = 0.325 eV) gözlenmesi nedeniyle yarı iletken davranış gösteren bu antiferromanyetik sistemin elektronik özelliği araştırılmıştır. Ayrıca, bu bileşik, tüm farklı tip manyetik fazlar için hesaplanan negatif oluşum enerji değerleri nedeniyle termodinamik kararlılığa ve yapısal sentezlenebilirliğe sahiptir

The first principles investigation of structural, electronic, mechanical and lattice dynamical properties of the B and N doped M2AX type MAX phases Ti2AlB0.5C0.5 and Ti2AlN0.5C0.5 compounds

Ti2AlB0.5C0.5 and Ti2AlN0.5C0.5 compounds which are called M2AX type MAX phases referred to as 211 and have hexagonal crystal structure with conform to P63/mmc space group, have been examined by using Generalized Gradient Approximation (GGA) in the Density Functional Theory (DFT) as implemented in CASTEP software package. In this study, the electronic, elastic, and lattice dynamical properties of these compounds have been investigated within the ab initio study. These compounds show metallic behavior since there is no band gap in the calculated electronic band structures. The estimated elastic constants of these compounds indicate that they are mechanically stable and their bonding nature is ionic and also, Ti2AlN0.5C0.5 compund has anisotropic character in mechanically whereas the behavior of Ti2AlB0.5C0.5 compound is nearly isotropic. Moreover, both of our compounds are brittle materials. Also, these compounds are dynamically stable since there are no soft modes in their plotted phonon dispersion curves

The First Principles Investigation of Structural, Electronic, Mechanical and Lattice Dynamical Properties of the B and N Doped M2AX Type MAX Phases Ti2AlB0.5C0.5 and Ti2AlN0.5C0.5 Compounds

Ti2AlB0.5C0.5and Ti2AlN0.5C0.5compoundswhich are calledM2AXtype MAX phasesreferred to as 211 andhavehexagonal crystal structure with conform to P63/mmcspace group, havebeen examinedby using Generalized GradientApproximation (GGA) in the Density Functional Theory (DFT)as implemented in CASTEPsoftware package. In this study, theelectronic, elastic, and lattice dynamical properties of these compounds have been investigatedwithintheab initiostudy. These compounds show metallic behavior since there is no band gap in the calculated electronic band structures.The estimated elastic constants of these compounds indicate that they are mechanically stable and their bonding nature is ionic and also, Ti2AlN0.5C0.5compund hasanisotropic character inmechanically whereas the behavior of Ti2AlB0.5C0.5compound is nearlyisotropic.Moreover, both of our compounds are brittle materials. Also, these compounds are dynamically stable since there are no soft modes in their plotted phonon dispersion curves

The mechanical and electronic properties of spinel oxides VX2O4 (X = Mn and Fe) by first principle calculations

We have performed first-principles density functional theory calculations within generalized-gradient approximation to obtain the mechanical properties and the electronic behavior of Vanadium based Spinel Oxides VX2O4 (X=Mn and Fe) which conform Fm-3m space group with 225 space number and are promising good candidates for spintronic applications due to their half-metallic band gaps (Eg=1.71 eV for VFe2O4 and Eg = 0.53 eV for VMn2O4) in the plotted spin-polarized electronic band structure. Also, the calculated negative formation enthalpies indicate that these materials have thermodynamic stability and structural synthesizability. Additionally, the calculated elastic constants by using stress-strain approach indicate mechanical stability of above-mentioned materials. © 2019 Author(s)