Ab-initio study of AlN in zinc-blende and rock-salt phases

Group III-nitrides are of great interest in both fundamental sciences and technical application. Most of the common nitrides are well known as hard and wide band gap semiconductor materials. In general they have been studied in zinc-blende and wurtzite phases. In this paper, we focus our attention to structural, electronic, phase transition and elastic properties of aluminum nitride (AlN) in zinc-blende and rock-salt phases. A little work has been reported either theoretically or experimentally on elastic and electronic properties of AlN; especially in RS phase. All the calculations are performed using the full-potential linearized augmented plane-wave approach plus local orbitals within the framework of density functional theory as implemented in the Wien2k code. The generalized gradient approximation based on the Perdew–Burke–Ernzerhof is used for the exchange and correlation functional. We determine the full set of first order elastic constants, C₁₁, C₁₂ and C₄₄ at zero pressure to confirm the mechanical stability and hardness, which have not been established either experimentally or theoretically for RS phase. In the study obvious phase transition from ZB phase to RS phase due to pressure effect has been obtained at 12.75 GPa.     

Redox‐Active Peptide‐Functionalized Quinquethiophene‐Based Electrochromic π‐Gel

An electrochromic system based on a self‐assembled dipeptide‐appended redox‐active quinquethiophene π‐gel is reported. The designed peptide‐quinquethiophene consists of a symmetric bolaamphiphile that has two segments: a redox‐active π‐conjugated quinquethiophene core for electrochromism, and peptide motif for the involvement of molecular self‐assembly. Investigations reveal that self‐assembly and electrochromic properties of the π‐gel are strongly dependent on the relative orientation of peptidic and quinquethiophene scaffolds in the self‐assembly system. The colors of the π‐gel film are very stable with fast and controlled switching speed at room temperature.     

A simple experimental method to generate partially coherent optical bottle beam

An experimental study is carried out to investigate a special kind of three-dimensional intensity distribution of a partially coherent optical beam known as optical bottle beam produced by using an annular aperture and lens combination (Lens Aperture System). In this paper, we are demonstrating the experimental results of our observations. The investigation also includes the effects of coherence modulation and central obstruction of the annular aperture (used in Lens Aperture System) on the resultant partially coherent optical bottle beam. The method discussed in this paper is simple and cost effective.     

Isotopic effects on non-linearity, molecular radius and intermolecular free length

Computation of non-linearity parameter (B/A), molecular radius (r _m) and intermolecular free length (L _f) for H₂O, C₆H₆, C₆H₁₂, CH₃OH, C₂H₅OH and their deuterium-substituted compounds have been carried out at four different temperatures, viz., 293.15, 303.15, 313.15 and 323.15 K. The aim of the investigation is an attempt to study the isotopic effects on the non-linearity parameter and the physicochemical properties of the liquids, which in turn has been used to study their effect on the intermolecular interactions produced thereof.