First-principles calculations to investigate the structural, electronic, elastic, vibrational and thermodynamic properties of the full-Heusler alloys X2ScGa (X = Ir and Rh)

This study has investigated ab initio pseudopotential calculations on the structural, electronic, elastic, vibrational and thermodynamic properties of the full-Heusler X2ScGa (X = Ir and Rh) alloys. The calculations have taken place under consideration of the generalized gradient approximation (GGA) of the density functional theory (DFT) with using the plane-wave ab initio pseudopotential method. According to the calculations, the major contribution to electronic states at the Fermi energy has been achieved by d orbitals, revealing a more active role for transition metals Ir (Rh) and Sc atoms. The reckonings point out that the Ir2ScGa and Rh2ScGa have metallic behavior at the equilibrium lattice constant with the density of states (DOS) at the Fermi level (N (EF)) of 1.412 states/eV and 1.821 states/eV, respectively. The results of the elastic constants showed that these compounds met the criteria for Born mechanical stability. It was also observed that they have a ductile structure and exhibit anisotropic behavior according to Pugh criteria. Besides, the full phonon spectra and their projected partial density of states of the alloys have been analyzed with the first-principle linear-response approach of the density-functional perturbation theory. All the alloys behaved dynamically stable in the L21 phase. Furthermore, internal free energy, entropy, specific heat capacity at constant volume and vibrational free energy changes of Ir2ScGa and Rh2ScGa alloys were analyzed and discussed between the temperature range of 0–800 K using the quasi harmonic approximation. According to the results, these alloys are potential candidate for industrial use. © 2020 Elsevier Lt

Mechanical, electronic, thermodynamic and vibrational properties of X2MgAl (X = Sc, Ti and Y) from first principles calculations

Due to growing interest to predict and design new potential Heusler alloys by using theoretical calculations and highly functional software, research on Heusler alloys has taken great attention. From this point of view, this study considers investigation of X2MgAl (X = Sc, Ti and Y) alloys by adopting first principles calculations for the first time. A thorough investigation has been carried out to reveal these alloys' mechanical, electronic, vibrational and thermodynamic properties. It is seen that all alloys have negative formation energies as -0.278 eV/atom for Sc2MgAl, -0.058 eV/atom for Ti2MgAl and -0.304 eV/atom for Y2MgAl which indicates synthesisability and thermodynamic stability. Mechanical stability investigations based on the elastic constants of alloys have revealed that all alloys are mechanically stable. The electronic band structures of alloys demonstrate that X2MgAl (X = Sc, Ti and Y) alloys are metallic since there is no energy gap near the Fermi level. Cauchy's pressures of alloys are found as -17.791 GPa for Sc2MgAl, 31.404 GPa for Ti2MgAl and -11.759 GPa for Y2MgAl which displays that Sc2MgAl and Y2MgAl are brittle and Ti2MgAl is ductile. The phonon dispersion curves are calculated along the lines of high symmetry within the first Brillouin region. Phonon frequencies are completely positive in the full Brillouin region, which proves the dynamic stability of the L2(1) phases of these alloys. Several thermodynamic properties such as Debye entropy, temperature and vibrational free energy are also computed and analysed. Debye entropies of alloys follow Ti2MgAl > Y2MgAl > Sc2MgAl relationship

Density functional theory investigation on structural, mechanical, electronic and vibrational properties of Heusler alloys AlXIr2 (X = Co, Cr, Cu, Fe and Zn)

This study focuses on the detailed investigation of full-Heusler AlXIr2 (X = Co, Cr, Cu, Fe and Zn) alloys. A first -principal plane-wave pseudopotential method based on density functional theory is adopted. The quantum -espresso package combined with the generalized gradient approach is used to reveal the structural, electronic, magnetic, mechanical and lattice dynamic properties of full-Heusler AlXIr2 (X = Co, Cr, Cu, Fe and Zn) alloys. The elastic constants are used to determine elastic stabilities of alloys based on Born criteria. The analysis showed that all alloys are elastically stable. Further detailed analysis has been carried out to reveal mechanical properties. It is found that all alloys are ductile and anisotropic. The electronic band structures are also obtained. All alloys except for AlCrIr2 are found to be metallic. AlCrIr2 has half-metallic nature. In addition, AlCrIr2, AlFeIr2 and AlCoIr2 has shown magnetic properties. The phonon spectra and density of states are investigated to examine dynamical stability. It is seen that all alloys exhibit dynamical stability due to having positive phonon frequencies

Bilimin Doğası Kapsamında Gözlem: Meteoroloji Gözlem Etkinliği Örneği

DergiPark: 484183tredBu çalışmanın amacı fen bilgisi öğretmenadaylarının gözlem yapmalarını ve yaptıkları gözlemler aracılığıyla havadurumuna ve bilimsel bilginin niteliklerine ilişkin çıkarımlarda bulunmalarınısağlamaktır. Nitel verilerden oluşan çalışma, durum araştırması desenine göredizayn edilmiştir. Çalışma süreci 2017-2018 bahar döneminde fen bilgisi eğitimianabilim dalı 4. sınıfında öğrenim görmekte olan ve astronomi dersine devameden 64 öğretmen adayı ile yürütülmüştür. Araştırma verileriyarı-yapılandırılmış görüşme formu ve doküman aracılığıyla toplanmıştır. Verianaliz sürecinde içerik analizi yöntemi kullanılmıştır. Araştırma sonuçlarınagöre, öğretmen adaylarının gözlem etkinliği süreci öncesinde günlük yaşamdakarşılaştıkları ve gözlemledikleri olayları bilimsel açıdan değerlendirmenoktasında eksiklik yaşadıkları görülmüştür. Etkinlik süreci sonrasında iseöğretmen adaylarının gözlemledikleri olayları eleştirel olarak değerlendirmeyeve bilimin doğasına ilişkin niteliklere odaklanarak açıklamaya başladıklarıgörülmüştür

Investigation of mechanical, elastic and thermodynamic properties of Ni2VAl compound

Bu çalışmada teknolojik öneme haiz Heusler ailesinden Ni2VAl bileşiğinin yapısal, mekanik ve termo dinamik özellikleri ilk prensipler yöntemi ile teorik olarak incelenmiştir. Öncelikle bileşiğin temel durumunu ve en düşük enerji seviyesini belirlemek için yapısal optimizasyon yapılmış, yapısal optimizasyon neticesinde elde edilen optimize parametreler kullanılarak elastik sabitler hesaplanmıştır. Hesaplanan örgü parametresi önceki çalışmalar ile uyum içeresindedir. Ayrıca belirlenen elastik sabitler mekanik kararlılık kriterlerini karşıladığından elastik modül, Vicker sertliği, erime sıcaklığı, Debye sıcaklığı, ses hızları, minimum termal iletkenlik ve anizotropi incelenmiştir. Çalışılan malzemenin Vicker sertliği ve sünek/kırılgan doğası analiz edilmiştir. Ayrıca iç enerji, titreşim enerjisi, entropi ve özgül ısı kapasitesi 0-800 K sıcaklık aralığında değerlendirilmiştir. Hesaplamalarda açık kaynak Quantum Espresso yazılımı ve bu yazılım ile dağıtımı yapılan thermo_pw paketi tercih edilmiştir. Yapılan çalışma ile Ni2VAl bileşiğinin mekanik kararlı, sünek, anizotrop ve yumuşak olduğu görüldü.In this study, the structural, mechanical, and thermodynamic properties of Ni2VAl compound from Heusler family, which has technological importance, were investigated theoretically by first principles method. Firstly, structural optimization was performed to determine the ground state and lowest energy level of the compound, and elastic constants were calculated using the optimized parameters obtained as a result of structural optimization. The calculated lattice parameter agrees with previous studies. In addition, elastic modulus, Vicker hardness, melting temperature, Debye temperature, sound velocities, minimum thermal conductivity and anisotropy were investigated since the determined elastic constants meet the mechanical stability criteria. The Vicker hardness and ductile/brittle nature of the studied material were analyzed. In addition, internal energy, vibrational energy, entropy, and specific heat capacity were evaluated in the temperature range of 0-800 K. In calculations, open-source Quantum Espresso software and thermo_pw package distributed with this software were preferred. With the study, it was seen that the Ni2VAl compound was mechanically stable, ductile, anisotropic, and soft

Investigation of the Mechanical, Electronic and Phonon Properties of X2ScAl (X = Ir, Os, and Pt) Heusler Compounds

In the present study, the second-order elastic constants and the electronic band structures of the X2ScAl (x = Ir, Os, and Pt) compounds crystallized in the L21 phase were calculated separately by using the ab-initio density functional theory. According to the results for the second-order elastic constants, these compounds met the Born mechanical stability criteria. Also, according to the Pugh criteria, they were found to have a ductile structure and to show anisotropic behavior. The microhardneses of the compounds were between 2 and 14 GPa, and the highest hardness was found in the Ir2ScAl (14.290 GPa) compound. In addition, the energy band structures of these compounds were calculated, and the crystals were found to have a metallic bond structure. All the computed data were compared with previously calculated results obtained with different methods. According to the findings obtained in the present study, in terms of its mechanical and electronic behaviors, Ir2ScAl was found to have better physical properties than Os2ScAl and Pt2ScAl. The phonon dispersion curves and their corresponding total and projected densities of states were investigated for the first time by using a linear-response approach in the context of density functional perturbation theory. The frequencies of the optical phonon modes of all compounds at the Γ point were 4.767, 7.504 and 9.271 THz for Ir2ScAl, 2.761, 7.985 and 9.184 THz for Os2ScAl and 2.012, 5.6952 and 8.118 THz for Pt2ScAl. The heat capacity Cv at constant volume versus temperature was calculated using a quasi-harmonic approach and the results are discussed. © 2020, The Korean Physical Society

Structural, mechanical and dynamical properties of XMnSb (X=Au and Ir) in the AlLiSi structure

Kübik AlLiSi yapıdaki XMnSb (X =Au ve Ir) bileşiklerinin yapısal, elektronik, elastik ve fonon özellikleri ilk prensip hesaplamalarıyla gerçekleştirildi. Optimize örgü sabiti ve hacim modülü hesaplandı ve mevcut verilerle karşılaştırıldı. Kübik AlLiSi yapıdaki XMnSb (X =Au ve Ir) bileşiklerinin elastik sabitleri (C11, C12ve C44) enerji zorlama metodu kullanılarak hesaplandı. AuMnSb ve IrMnSb bileyapıları spin yukarı ve spin aşağı eşleşmeleri için hesaplanarak mevcut verilerle karşılaştırıldı. Fonon dağılım eğrileri ve onlara karşılık gelen durum yoğunlukları yoğunluk fonksiyonel pertürbasyon teorisi çerçevesinde lineer tepki yaklaFirst principle calculations have been carried out on the structural, electronic, elastic, and phonon properties of XMnSb (X =Au and Ir) in the cubic AlLiSi structure. The optimized lattice constant and bulk modulus are calculated and compared with the available data. The elastic constants (C11, C12 and C44) in the cubic AlLiSi structure for XMnSb (X =Au and Ir) are computed using the energy?strain method. Spin polarized band structures of AuMnSb and IrMnSb for majority?spin and minority spin alignments are calculated and analyzed in comparison with the existing findings. Phonon dispersion curves and their corresponding total and projected densities of states have been obtained for the first time using a linear response approximation in the framework of the density functional perturbation theor

Mechanical and dynamical properties of Co3Al and Co3Ta alloys in L12 phase

Yoğunluk Fonksiyonel Teorisi ile Co3Al ve Co3Ta alaşımlarının yapısal, elastik, elektronik ve titreşimözellikleri incelenmiştir. Denge durumundaki örgü sabitleri, hacim modülü ve hacim modülünün basıncagöre türevleri L12 yapıda hesaplandı ve eldeki verilerle karşılaştırıldı. Elastik sabitlerinin nümerik ilk prensiphesaplamaları, Co3Al ve Co3Ta alaşımları için C11, C12 ve C44 hesaplandı. Co3Al ve Co3Ta alaşımlarının elektronik bant yapısı, toplam ve kısmi durum yoğunlukları, toplam manyetik momentleri hesaplandı. Her iki alaşım için yapılan elektronik hesaplamalardan alaşımların metalik karakterde oldukları görüldü. Fonondispersiyon eğrileri ve onlara karşılık gelen toplam ve parçalı durum yoğunlukları ilk kez yoğunlukfonksiyonel pertürbasyon teorisi çerçevesinde lineer-tepki yaklaşımı kullanılarak elde edildi. Co3Al ve Co3Ta'nın ? noktasındaki optik fonon modlarının frekansları sırasıyla, Co3Al için 4,46; 6,095 ve 10,35 THz ve Co3Ta için 4,83; 6,11 ve 6,86 THz olarak bulundu. Son olarak sıcaklığa karşı sabit hacimde ısı sığası yarıharmonik yaklaşım kullanılarak hesaplandı ve tartışıldı.The structural, elastic, electronic and vibrational properties of Co3Al and CoTa alloys with density functional theory have been investigated. The lattice constants, bulk modulus and its pressure derivative areevaluated and compared with the available data. The numerical first principles calculations of the elasticconstants were used to calculate C11, C12 and Cfor CoAl and Co3Ta alloys. The electronic band structure, electronic total and partial densities of states, and total magnetic moment of the Co3Al and Co3Ta alloys are computed and analyzed in comparison with the existing findings. From the electronic calculations made forboth alloys, it was found that the alloys were metallic in nature. Phonon-dispersion curves and their corresponding total and projected densities of states have been obtained for the first time using a linearresponse in the framework of the density functional perturbation theory. The frequencies of the opticalphonon modes of both alloys are calculated and found to be 4.46, 6.095 and 10.35 THz for Co3Al, 4.83, 6.11 and 6.86 THz for CoTa. Finally, specific heat capacity at a constant volume versus temperature CV of Co3Al and Co3Ta alloys is calculated and discussed using the quasi harmonic approximation

First-Principles Study on PdMnSn and PtMnSn Compounds in C1 b Structure

The phase stability, the electronic, mechanic and lattice dynamical properties of C1b-type PdMnSn and PtMnSn compounds were investigated using first principles density functional calculations within the generalized gradient approximation. The computed lattice constants of PdMnSn and PtMnSn compounds were in line with the experimental and theoretical data in the published literature. The elastic constants in the C1b structure for PdMnSn and PtMnSn compounds were carried out using the energy-strain method. The computed values of three independent elastic constants, both compounds are mechanically stable in the C1-type crystal structure and met the stability criteria. The electronic structure, total and partial density values of states, and total magnetic moment of these compounds were calculated and the evaluations were carried out by comparing with the existing results. Dynamic properties of PdMnSn and PtMnSn compounds were obtained using the density functional perturbation theory. Both of the compounds were dynamically stable due to the absence of the imaginary phonon frequencies. In addition, it was found that the compounds had a rapid rise in specific heat capacities from 0 to 300 K

Meme kanseri risk ve prognozunda survivin geninin etkileri

ÖzAmaçKanser gelişiminde genetik yapıda meydana gelen değişimlerin birikiminin protoonkogenlerin aktivasyonunu ya da tümör baskılayıcı genlerin inaktivasyonunu uyararak hücre proliferasyonu ile programlanmış hücre ölümü arasındaki dengenin bozulmasına neden olduğu bildirilmiştir. Apoptoz inhibitör protein ailesinin (IAP) bir üyesi olarak survivin, karsinogenez sürecinde önemli rol oynamaktadır. Çeşitli çalışmalar, survivin promoter bölgesinde bulunan polimorfizmlerin, kanserin genetik duyarlılığının belirlenmesinde önemli olabileceğini düşündürmektedir. Bu çalışmada meme kanserli hastalarda survivin−31 ve−625G/C gen polimorfizmlerinin olası etkilerinin incelenmesi amaçlanmıştır.yöntemlerÇalışmada 160 meme kanseri vakası ile 153 sağlıklı kontrol grubu, Polimeraz Zincir Reaksiyon-Restriksiyon Uzunluk Polimorfizmi (PCR-RFLP) metodolojisi kullanılarak genotiplendirildi.BulgularAraştırmamız sonucunda−31 ve−625G/C polimorfizm genotip dağılım ve allel frekansları açısından karşılaştırıldığında hasta ve kontrol grupları arasında istatistiksel olarak anlamlı bir fark gözlenmemiştir. Ancak, survivin−625C/G polimorfizm homozigot (GG/CC) genotipi tümör nekrozu olan hastalarda istatistiksel olarak yüksek oranda saptanmıştır (p=0.047).SonuçÇalışma bulgularımız, survivin−625C/G polimorfizminin tümör prognozu ile ilişkili olabileceğini düşündürmektedir. Ancak sonucumuzun dahabüyük örnek gruplarında doğrulanması gerektiğini ve bu alanda yapılacak daha kapsamlı araştırmalarda değerlendirilebileceği kanaatindeyiz