Calculation of electronic properties of amorphous alloys

We describe the application of the locally-self-consistent-multiple-scattering (LSMS)[1] method to amorphous alloys. The LSMS algorithm is optimized for the Intel XP/S-150, a multiple-instruction-multiple-data parallel computer with 1024 nodes and 2 compute processors per node. The electron density at each site is determined by solving the multiple scattering equation for atoms within a specified distance of the atom under consideration. Because this method is carried out in real space it is ideal for treating amorphous alloys. We have adapted the code to the calculation of the electronic properties of amorphous alloys. In these calculations we determine the potentials in the atomic sphere approximation self consistently at each site, unlike previous calculations[2] where we determined the potentials self consistently at an average site. With these self-consistent potentials, we then calculate electronic properties of various amorphous alloy systems. We present calculated total electronic densities of states for amorphous Ni$_{80}$P$_{20}$ and Ni$_{40}$Pd$_{40}$P$_{20}$ with 300 atoms in a supercell.Comment: 10 pages, plain tex, 2 figures. Paper accepted for publication in Proceedings of LAM-9 and Journal of non-Crystalline Solids. Please request preprints from J.C. Swihart ([email protected]

Large Pyroelectric Response from Reactively Sputtered Aluminum Nitride Thin Films

We report the pyroelectric response of c-axis oriented, undoped, wurtzite, aluminum nitride reactively sputtered onto polished silicon wafers. The voltage between a metallic contact on the AlN surface and the n+ -doped silicon substrate was monitored during pulsed infrared, radiant heating. From analysis of the data, a pyroelectric voltage coefficient, PV, in excess of 0.5 x 106 V/m/K was extracted for films in the 600 to 2500 Å thickness range

Effects of thermal relaxation on an amorphous superconducting Zr--Rh alloy

The electronic and superconducting properties of an amorphous transition metal alloy are used to evaluate the effects of low temperature annealing. It is observed that the superconducting transition temperature and the electrical resistivity relax exponentially in time from their initial value to a final relaxed value. From this an activation energy for the relaxation process is derived and an explanation is suggested which involves internal stress

Salamander Abundance along Road Edges and within Abandoned Logging Roads in Appalachian Forests

Roads may be one of the most common disturbances in otherwise continuous forested habitat in the southern Appalachian Mountains. Despite their obvious presence on the landscape, there is limited data on the ecological effects along a road edge or the size of the “road-effect zone.” We sampled salamanders at current and abandoned road sites within the Nantahala National Forest, North Carolina (U.S.A.) to determine the road-effect zone for an assemblage of woodland salamanders. Salamander abundance near the road was reduced significantly, and salamanders along the edges were predominantly large individuals. These results indicate that the road-effect zone for these salamanders extended 35 m on either side of the relatively narrow, low-use forest roads along which we sampled. Furthermore, salamander abundance was significantly lower on old, abandoned logging roads compared with the adjacent upslope sites. These results indicate that forest roads and abandoned logging roads have negative effects on forest-dependent species such as plethodontid salamanders. Our results may apply to other protected forests in the southern Appalachians and may exemplify a problem created by current and past land use activities in all forested regions, especially those related to road building for natural-resource extraction. Our results show that the effect of roads reached well beyond their boundary and that abandonment or the decommissioning of roads did not reverse detrimental ecological effects; rather, our results indicate that management decisions have significant repercussions for generations to come. Furthermore, the quantity of suitable forested habitat in the protected areas we studied was significantly reduced: between 28.6% and 36.9% of the area was affected by roads. Management and policy decisions must use current and historical data on land use to understand cumulative impacts on forest-dependent species and to fully protect biodiversity on national landsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73456/1/j.1523-1739.2006.00571.x.pd