1,720,989 research outputs found
First-Principles Study on the Structural, Elastic, Electronic and Vibrational Properties of Scandium Based Intermetalic Compounds (ScX, X = Co, Rh and Ir) Under Pressure
No full textWOS: 000393919300002The structural, electronic, mechanic and vibrational properties of B2-type scandium intermetallic compounds, ScCo, ScRh and ScIr, are studied by performing ab-initio density functional theory using the Vienna Ab initio Simulation Package (VASP). The exchange correlation potential within the generalized-gradient apraximation (GGA) of projected augmented plane-wave (PAW) is used. The calculated structural parameters, such as the lattice constant (a(0)), bulk modulus (B) and its pressure derivative (B) are calculated in the CsCl-(B2) structure. The electronic properties of the ScCo, ScRh and ScIr compounds are quantitatively analyzed using band structure and density of states (DOS). The electronic properties such as band structure and DOS reveal that considered scandium compounds are metallic in nature with large overlap at Fermi level. The elastic constants of these compounds are investigated using stress-strain method. Present results for elastic constants show that considered compounds are mechanically stable. Furthermore the effect of pressure on electronic properties and elastic constants are also investigated. The computed phonon dispersion curves show that these compounds are dynamically stable. The obtained results are compared with the available experimental and theoretical studies
First principle study of structural, electronic, mechanical, dynamic and optical properties of half-Heusler compound LiScSi under pressure
No full textWOS: 000450655200002In this study, several physical properties of LiScSi compound with MgAgAs phase were investigated via the plane-wave pseudo-potential technique in density functional theory (DFT). The calculated total energy-atomic volume was fitted to the Murnaghan equation of state in order to obtain bulk modulus, their first derivatives and the lattice constant. These results were compared to findings of recent literature. Afterwards, the partial density of states (PDOS) and charge density differences were used to evaluate the electronic band structure of LiScSi under pressure. By analysing elastic properties (shear modulus, Poisson ratio, Young's modulus, etc.) of the material, it has been shown that MgAgAs phase of the compound is mechanically stable under pressure. Moreover, the dynamical stability of this compound is calculated by means of the phonon dispersion curves and one-phonon DOS. Finally, the optical properties and related parameters (refractive index, dielectric function, and loss function) of LiScSi were examined with subject to different pressures
Investigation of electronic and optical properties of organic poly(3-hexylthiophene)(P3HT) polymers used in solar cells
No full textPoli(3-hekziltiyofen-2,5-diil) (P3HT) ve türevleri iyi organik yarı iletkenler olup fotovoltaik sistemler, organik ışık yayan diyotlar gibi birçok alanda çeşitli uygulamaları vardır. Bu çalışmada P3HT'nin yapısına Klor ve Flor katkılayarak P3HT polimer zincirini oluşturan monomerlerin temel fiziksel ve kimyasal özellikleri teorik olarak incelendi. Hesaplamalarda Gaussian 09 ve yapıların görsellere dönüştürülmesinde GaussView 5.0 paket programları kullanıldı. İzole edilen molekülün bağ uzunlukları ve bağ açılarının katkılanmış P3HT'den daha fazla olduğu bulundu. Flor katkılı P3HT ve klor katkılı P3HT için bant aralığı hesaplandı. Katkılanmış moleküllerin daha düşük kimyasal sertlik değerlerine sahip oldukları için izole edilmiş formlarından daha reaktif olarak bulunmuştur. Doğrusal olmayan optik (NLO) özelliklere ilişkin sonuçlar, katkılı P3HT'nin birinci dereceden hiper polarize edilebilirlik özelliğinin iyi olduğunu göstermektedir. UVVis absorpsiyon değerleri ve açık devre voltajı da hesaplandı. Sonuçlara göre katkılı moleküller, elektron transferlerinin iyi olması nedeniyle fotovoltaik cihazlar için potansiyel uygulamalara sahiptir.Poly(3-hexylthiophene-2,5-diyl) (P3HT) and its derivatives are good organic semiconductors and have various applications in many fields such as photovoltaic systems and organic light-emitting diodes. In this study, the basic physical and chemical properties of the monomers that form the P3HT polymer chain by adding Chlorine and Fluorine to the structure of P3HT were examined theoretically. Gaussian 09 was used in the calculations and GaussView 5.0 software packages were used to convert the structures into visuals. It was found that the bond lengths and bond angles of the isolated molecule were greater than the doped P3HT. The band gap was calculated for fluorine-doped P3HT and chlorine-doped P3HT. Doped molecules were found to be more reactive than their isolated forms because they had lower chemical hardness values. Results on nonlinear optical (NLO) properties show that doped P3HT has good first-order hyperpolarizability. UV-Vis absorption values and open circuit voltage were also calculated. According to the results, the doped molecules have potential applications for photovoltaic devices due to good electron transfer
Single Gaussian distribution of barrier height in Al/PS-ZnPc/p-Si type Schottky barrier diode in temperature range of 120-320 K
No full textWOS: 000342157500030Possible current-transport mechanism in aluminum/polystrene-zincphthalocyanine/ptype silicon Schotky barrier diode (Al/PS-ZnPc/p-Si; SBD), for the forward bias current-voltage (I-V) characteristics were carried out in the temperature range of 120-320 K. The high value of ideality factor (n), especially at low temperatures, was attributed to the existence of PS layer, barrier in-homogeneities and particular density distribution of surface states between metal and semiconductor. An abnormal decrease in the zero-bias barrier height (BH) and increase in n with decreasing temperature which leads to non-linearity in the Richardson plot, have been observed. Linear relationship between BH and n was also observed. BH was plotted as a function of q/2kT to obtain evidence of Gaussian distribution (GD) of the BHs. The mean BH and its standard deviation (sigma) were obtained as 1.03 eV and 0.117 V from the slope and intercept of this plot, respectively. Thus, the modified ln(Io/T-2) - q(2)sigma o(2)/2k(2)T(2) versus q/kT plot gives mean BH and the modified Richardson constant as 1.043 eV and 29.824 A cm(-2) K-2, respectively. This value of the Richardson constant is very close to the theoretical value of 32 A cm(-2) K-2 for p-type Si. Therefore, non-ideal behavior of forward-bias I-V characteristics in Al/PS-ZnPc/p-Si might be successfully explained in terms of the thermionic emission mechanism with single GD of BHs.scientific research unit of Amasya University [FMB-BAP-13-038, FMB-BAP-13-059]Authors want to express their great acknowledges to the scientific research unit of Amasya University for the financial support to this study with Grant Numbers of FMB-BAP-13-038 and FMB-BAP-13-059, and executives of Amasya University Central Research Laboratory for their kind understanding of using their facilities
Crystal and Molecular Structure of 2-(4-Ethoxyphenyl)isoindoline-1,3-dione
No full textWOS: 000453256000010The 2-(4-ethoxyphenyl)isoindoline-1,3-dione has been synthesized and characterized by X-ray single-crystal diffraction. The compound crystallizes in the orthorhombic sp. gr. Pna2(1) with four molecules in the unit cell and one molecule in the asymmetric unit. The molecular structure is not planar. The dihedral angle between the isoindoline and phenyl rings is 55.69(7)degrees. In the crystal structure, molecules are linked together by intermolecular C-HO hydrogen bonds.Research Centre of Amasya University [FMB-BAP 15-092]This study was supported financially by the Research Centre of Amasya University (project no. FMB-BAP 15-092)
ATOMLARIN VE MOLEKÜLLERİN NiAl YÜZEYLERİNE TUTUNMASININ YOĞUNLUK FONKSİYONELİ TEORİSİ İLE İNCELENMESİ
No full textBu çalışmada, O, S, H, OH, SH, H2O ve H2S'nin NiAl(110)-(2х2) yüzeyi üzerinde tutunma enerjileri ve taban durumundaki yapıları atomik boyutta incelenmiştir. Hesaplamalar, psüdopotansiyel ve yoğunluk fonksiyoneli teorisine dayanmaktadır. Moleküllerin yüzey üzerindeki tutunma noktaları ile uyumlu bir şekilde S ve H için tutunma noktası olarak 2Ni–Al ve O için de 2Al–Ni noktası bulunmuştur. İncelenen atom ve moleküllerin NiAl(110) yüzeyine tutunmasının reaksiyon yolu hesabı olan NEB (The Nudged Elastic Band) şekline bakılmıştır. NEB hesaplamalarında tutunma enerjisinde bir enerji bariyeri gözlenmiştir. Elde edilen sonuçlar önceki deneysel ve teorik çalışmalarla karşılaştırılmıştır
A comparative theoretical study of three isomeric benzotriazolylpropanamides
No full text659-670Structural, vibrational and molecular electrostatic potential of the isomeric benzotriazolylpropanamides (2-methyl-3-(1Hbenzotriazol-
1-yl)propanamide, 2-methyl-3-(2H-benzotriazol-2-yl)propanamide and N,N-dimethyl-3-(1H-benzotriazol-1-
yl)propanamide) molecules in the ground state have been investigated using different theoretical methods with same basis
set. The spectral results obtained from the quantum chemical calculations are in a good agreement with the experimental
results. Thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated and
discussed by using same methods. Besides, electronic and nonlinear optical properties were investigated in detail. Nonlinear
optical property calculations of the molecules indicate that the materials can be used as nonlinear optic materials
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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