First-principle electronic, elastic, and optical study of cubic gallium nitride

The ab initio pseudopotential (PP) method within the generalized gradient approximation (GGA) has been used to investigate the electronic, elastic constants, and optical properties of zinc-blende GaN. An underestimated band gap along with higher DOS and squeezed energy bands around the fermi level is obtained. The d-band effect is briefly discussed for electronic band structure calculations. With the help of elastic constants, acoustic wave speeds are calculated in [100], [110], and [111] planes. The dielectric constant, refractive index, and its pressure coefficient are well illustrated. The effect of hydrostatic pressure is explicated for all these properties. The results of the present study are evaluated with the existing experimental and first-principle calculations.     

Influences of Marangoni convection and variable magnetic field on hybrid nanofluid thin-film flow past a stretching surface

Investigations on thin-film flow play a vital role in the field of optoelectronics and magnetic devices. Thin films are reasonably hard and thermally stable but quite fragile. The thermal stability of a thin film can be further improved by incorporating the effects of nanoparticles. In the current work, a stretchable surface is considered upon which hybrid nanofluid thin-film flow is taken into account. The idea of augmenting heat transmission by making use of a hybrid nanofluid is a focus of the current work. The flow is affected by variations in the viscous forces, along with viscous dissipation effects and Marangoni convection. A time-constrained magnetic field is applied in the normal direction to the flow system. The equations governing the flow system are shifted to a non-dimensional form by applying similarity variables. The homotopy analysis method is employed to find the solution to the resultant equations. It is noticed in this study that the flow characteristics decline with augmentation of magnetic, viscosity and unsteadiness parameters while they increase with enhanced values of thin-film parameters. Thermal characteristics are supported by increasing values of the Eckert number and the unsteadiness parameter and opposed by the viscosity parameter and Prandtl number. The numerical impact of different emerging parameters upon skin friction and the Nusselt number is calculated in tabular form. A comparison of current work with established results is carried out, with good agreement.     

Simultaneous operation of dibenzothiophene hydrodesulfurization and methanol reforming reactions over Pd promoted alumina based catalysts

In the current study simultaneous reactions of hydrodesulfurization(HDS) of dibenzothiophene(DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic(Co-Mo/Al2O3 and Ni-Mo/Al2O3) and tri-metallic(Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3) catalyst systems which were prepared by incipient impregnation method.In situ hydrogen utilization and low Pd loadings were the major targets of this study.For comparison purpose,catalytic activity was separately determined for both the methanol reforming and HDS of DBT reactions as well.Ni based catalysts were confirmed with better activity than Co ones for both the reactions with Pd promoted ones ranking at the top i.e.Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 where Pd-Ni-Mo/Al2O3 showed 91% DBT conversion at 380 ℃ and 12 h reaction time.Some of the selected organic additives on catalytic activity were tested for their effect toward HDS reaction which was unique with close relation to their chemical nature.Reaction products were quantitatively and qualitatively analyzed via HPLC and GC-MS techniques respectively which helped in elucidating reaction mechanism.     

Structural modifications of AlInN/GaN thin films by neon ion implantation

To study ion beam induced modifications into MOCVD grown wurtzite AlInN layers, neon ions were implanted on the samples with four doses ranging from 10¹⁴ to 9×10¹⁵ ions/cm²$9\times {10}^{15}\text{ions}/{\text{cm}}^2$. Structural characterization was carried out by X-ray diffraction and Rutherford backscattering spectroscopy (RBS) techniques. XRD analysis revealed that GaN related peak for all samples remains at its usual Bragg position of 2θ=34.56°$2\theta =34.56\mathrm{°}$ whereas a shift in AlInN peak takes place from its position of 2θ=35.51°$2\theta =35.51\mathrm{°}$ for as-grown sample. Rutherford back scattering (RBS) analysis indicated that peak related to Ga atoms in capping layer provided evidence of partial sputtering of GaN cap layers. Moreover, Al peak position is shifted towards lower channel side and width of the signal is increased after implantation, which pointed to the inwards migration of Al atoms away from the AlInN surface. The results suggested that partial sputtering of cap layer has taken place without uncovering the underneath AlInN layer.     

Structural,electronic, and optical properties of Cd-halide-based inorganic LiCdX3 (X = F,Cl) perovskites for photovoltaic applications: A density functional theory study

Halide base perovskite LiCdX₃ (X = F, Cl) is tested by CASTEP (Cambridge Serial Total Energy Package) based on density function theory (DFT). The presented discussion is to explore the structural, electronic, and optical properties of LiCdX₃ (X = F, Cl). The calculated values of the lattice parameter are found to be 3.8 Å and 5.27 Å of LiCdF₃ and LiCdCl₃ respectively. The ideal structure of LiCdX₃ (X = F, Cl) is cubic and dynamically stable. Electronic properties show that materials are semiconductors. The results from band structure are further evaluated by the total and partial density of states. The partial and total density of states confirms the degree of localization of electrons. In optical properties, the highest absorption coefficient is observed in LiCdCl₃. The material is half metallic and has a narrow indirect band gap which may be used in photovoltaic applications.     

Physicochemical Study of Some Thiobarbiturate Derivatives and Their Interaction with DNA in Aqueous Media

Russian Journal of Physical Chemistry A - The aim of this study is to investigate the physicochemical behavior of some selected thiobarbituartes and explore their interaction with ds-DNA. To the...     

Palladium catalysed tandem cyclisation-anion capture processes. Part 8 : In situ and preformed organostannanes. Carbamyl chlorides and other starter species

A sequential one-pot process is reported involving in situ, palladium catalysed, formation of a series of tributylstannyl-1,2-carbo and heterocyclic dialkylidene-5-membered rings from the corresponding 1,6-diynes and Bu₃SnH. These substrates and other organostannanes are then combined with carbamyl chlorides and iodobenzenes containing proximate alkene and alkynyl groups in palladium catalysed cyclisation-anion capture cascades affording a diverse range of heterocycles in good yield.     

Bis[1‐(pyridin‐2‐yl)­ethano­ne‐κN 4‐phenyl­thio­semicarbazonato‐κ2N4,S]­manganese(II)

One half of the mol­ecule of the title complex, [Mn(C₁₄H₁₃N₄S)₂], is related to the other half by a twofold axis passing through the Mn atom. This high‐spin Mn atom is six‐coordinated, in an octahedral geometry, by the azomethine N, the pyridyl N and the thiol­ate S atom of two planar 1‐­(pyridin‐2‐yl)­ethanone N(4)‐phenyl­thio­semicarbazone lig­ands. In the crystal, the mol­ecules are interconnected by N—­H?S and C—H?N interactions, forming a three‐dimensional network.     

11‐Methyl‐12a‐phenyl‐9a,12a‐dihydrophenanthro[9′,10′:5,6][1,4]dioxino[2,3‐d]oxazole and 9a‐(10‐hydroxyphenanthren‐9‐yl)‐11,12a‐diphenyl‐9a,12a‐dihydrophenanthro[9′,10′:5,6][1,4]dioxino[2,3‐d]oxazole

In the title compounds, C₂₄H₁₇NO₃, (I), and C₄₃H₂₇NO₅, (II), the dioxine ring is not planar and tends toward a boat conformation. The oxazoline ring adopts a twisted conformation in mol­ecule (I) but is essentially planar in mol­ecule (II). The configuration of the dioxine–oxazoline system is determined by the sp³ state of the two shared atoms. The phenanthrene moiety is nearly coplanar with the dioxine ring, while the phenyl ring is perpendicular to the attached oxazole ring. The triclinic unit cell of (II) contains two crystallographically independent mol­ecules related by a pseudo‐inversion centre.