46 research outputs found
Electronic and structural properties of superconducting MgB, CaSi and related compounds
We report a detailed study of the electronic and structural properties of the
39K superconductor \mgbtwo and of several related systems of the same family,
namely \mgalbtwo, \bebtwo, \casitwo and \cabesi. Our calculations, which
include zone-center phonon frequencies and transport properties, are performed
within the local density approximation to the density functional theory, using
the full-potential linearized augmented plane wave (FLAPW) and the
norm-conserving pseudopotential methods. Our results indicate essentially
three-dimensional properties for these compounds; however, strongly
two-dimensional -bonding bands contribute significantly at the Fermi
level. Similarities and differences between \mgbtwo and \bebtwo (whose
superconducting properties have not been yet investigated) are analyzed in
detail. Our calculations for \mgalbtwo show that metal substitution cannot be
fully described in a rigid band model. \casitwo is studied as a function of
pressure, and Be substitution in the Si planes leads to a stable compound
similar in many aspects to diborides.Comment: Revised version, Phys.Rev.B in pres
The First VERITAS Telescope
The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic
Radiation Imaging Telescope Array System) has been in operation since February
2005. We present here a technical description of the instrument and a summary
of its performance. The calibration methods are described, along with the
results of Monte Carlo simulations of the telescope and comparisons between
real and simulated data. The analysis of TeV -ray observations of the
Crab Nebula, including the reconstructed energy spectrum, is shown to give
results consistent with earlier measurements. The telescope is operating as
expected and has met or exceeded all design specifications.Comment: Accepted by Astroparticle Physic