First principles study of structural and electronic properties of different phases of boron nitride

A theoretical study of structural and electronic properties of the four phases of BN (zincblende, wurtzite, hexagonal and rhombohedral) is presented. The calculations are done by full potential (linear) augmented plane wave plus local orbitals (APW+lo) method based on the density functional theory (DFT) as employed in WIEN2k code. Using the local density approximation (LDA) and generalized gradient approximation (GGA-PBE) for the exchange correlation energy functional, we have calculated lattice parameters, bulk modulus, its pressure derivative and cohesive energy. In order to calculate electronic band structure, another form of the generalized gradient approximation proposed by Engel and Vosko (GGA-EV) has been employed along with LDA and GGA-PBE. It is found that all the three approximations exhibit similar band structure qualitatively. However, GGA-EV gives energy band gap values closer to the measured data. Our results for structural and electronic properties are compared with the experimental and other theoretical results wherever these are available.     

PROTON-AMTIPROTOM ELASTIC SCATTERING AT HIGH ENERGIES

The differential cross sections for high energy P P elastic scattering showing structure near -t=1.5 (GeV/c)² for P_L=50,100 and 200 GeV/c together with total cross sections for 50≤P_L≤280 GeV/c, and with -t extending up to 5(GeV/c)² have been fitted by using a dipole pomeron model.     

Structural,morphological and mechanical properties of laser-irradiated copper using continuous wave diode laser

Laser irradiation effects on morphological, structural and mechanical properties of copper are explored. The targets are exposed by employing low-cost continuous wave (CW) laser (wavelength of 532?nm) in air. The surface morphology, structural and mechanical modification of irradiated targets was investigated by scanning electron microscopy (SEM) (Fei, Quanta 250), an X-ray diffractrometer (XRD) (DMAX III ARigaku, Japan) and a Vickers hardness tester, respectively. The SEM analysis revealed the exfoliation sputtering, electronic sputtering, thermal stresses and cracks. The grain size, dislocation line density, relative intensity and d-spacing of irradiated metals were studied by XRD. Micro hardness is found to increase with the increase in time of laser irradiation, in accordance with the Vickers hardness tester. This work provides a cost-effective, user-friendly and easy-to-handle study of several properties of irradiated targets with good results.     

Study of fermilab data for the reaction π−p → π0n

Fermilab data for the angular distribution measurements of the reaction ^–p ⁰n are investigated and it is shown that a good fit with experiment is obtained by using a simple Regge pole model with phenomenological residue functions. The energy dependence in this case is found to be different from that for the d/dt data obtained at Serpukhov.Work supported by the Pakistan Science Foundation under contract No. P-PU-PHY(11/1).     

Physical Properties of III-Antiminodes --- a First Principles Study

A comprehensive first principles study of III-Antimonide binary compounds ishardly found in literature. We report a broad study of structural and electronicproperties of boron antimonide (BSb), aluminium antimonide (AlSb), galliumantimonide (GaSb) and indium antimonide (InSb) in zincblende phase based on density functional theory (DFT). Our calculations are based onFull-Potential Linearized Augmented Plane wave plus local orbitals(FP-L(APW+lo)) method. Different forms of exchange-correlation energyfunctional and corresponding potential are employed for structural andelectronic properties. Our computed results for lattice parameters, bulkmoduli, their pressure derivatives, and cohesive energy are consistent withthe available experimental data. Boron antimonide is found to be the hardestcompound of this group. For band structure calculations, in addition to LDAand GGA, we used GGA-EV, an approximation employed by Engel and Vosko. The band gap results with GGA-EV are of significant improvement over the earlier work.     

PROTON-ANTIPROTON SCATTERING AT COLLIDER ENERGIES

The recent measurements of differential and total cross sections, the ratio of the integrated and total cross sections and the values of the slope parameter at Collider energy have been simultaneously fitted for the first time by using a pole+cut model.     

STUDY OF ≡-P ELASTIC SCATTERING

The recently measured differential, elastic and total cross section for ≡^-P elastic scattering at 102 and 135 GeV/c have been fitted by using simple Regge pole model with phenomenological residue fmctions.     

STUDY OF THE REACTION K-p→ηΛ

It is shown that at high energy all available data for differential and integrated cross sections and Λ-polarisation in the reaction K^-p→ηΛ can be fitted by using a simple Regge pole model with phenomenological residue functions. The characteristics of real and imaginary parts of the helicity amplitudes are also examined.     

Total Cross Sections at High Energies - An Update

Current and future measurements for the total cross sections at E-811, PP2PP, CSM, FELIX, and TOTEMhave been analyzed using various models. In the light of this study an attempt has been made to focus on the behaviorof total cross section at very high energies.