Electronic Structure of Te and As Covered Si(211)

Electronic and atomic structures of the clean, and As and Te covered Si(211) surface are studied using pseudopotential density functional method. The clean surface is found to have (2 X 1) and rebonded (1 X 1) reconstructions as stable surface structures, but no \pi-bonded chain reconstruction. Binding energies of As and Te adatoms at a number of symmetry sites on the ideal and (2 X 1) reconstructed surfaces have been calculated because of their importance in the epitaxial growth of CdTe and other materials on the Si(211) surface. The special symmetry sites on these surfaces having the highest binding energies for isolated As and Te adatoms are identified. But more significantly, several sites are found to be nearly degenerate in binding energy values. This has important consequences for epitaxial growth processes. Optimal structures calculated for 0.5 ML of As and Te coverage reveal that the As adatoms dimerize on the surface while the Te adatoms do not. However, both As and Te covered surfaces are found to be metallic in nature.Comment: 17 pages, 9 figures, accepted for publication in Phys. Rev.

Effect of Dynamical SU(2) Gluons to the Gap Equation of Nambu--Jona-Lasinio Model in Constant Background Magnetic Field

In order to estimate the effect of dynamical gluons to chiral condensate, the gap equation of SU(2) gauged Nambu--Jona-Lasinio model, under a constant background magnetic field, is investigated up to the two-loop order in 2+1 and 3+1 dimensions. We set up a general formulation allowing both cases of electric as well as magnetic background field. We rely on the proper time method to maintain gauge invariance. In 3+1 dimensions chiral symmetry breaking ($\chi$SB) is enhanced by gluons even in zero background magnetic field and becomes much striking as the background field grows larger. In 2+1 dimensions gluons also enhance $\chi$SB but whose dependence on the background field is not simple: dynamical mass is not a monotone function of background field for a fixed four-fermi coupling.Comment: 20 pages, 5 figure

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Not AvailableAim: Increase in agricultural productivity with minimal energy utilization without any adverse impact on environment is the pre-requisite of present agricultural practices through best agronomic management of crop production. The present investigation aimed to identify the most energy efficient cropping system and nutrient supply option which exert minimal impact on environment. Methodology: The experiment was carried out for two consecutive years at Indian Agricultural Research Institute, New Delhi for evaluation of 4 soybean-based cropping systems with 5 nutrient supply options in respect of energy parameters as well as carbon emission equivalents. The different inputs used in raising the crops and output of crops were converted into energy and carbon equivalents using standard conversion factors and used for computation of different energy and carbon efficiency indices. Results: The soybean–potato–mungbean system recorded significantly highest system productivity in terms of soybean seed-equivalent yield (7.68 t ha-1). But soybean–chickpea–fodder sorghum system recorded highest net energy (333.9 × 103 MJ ha-1), energy efficiency (9.56), energy productivity (179 g MJ-1), energy profitability (8.6 MJ ha-1), human energy profitability (105.2) and energy intensiveness (6.76). Soybean–chickpea–fodder sorghum system maintained higher carbon output and carbon efficiency which were 22.9 and 15.6% higher over soybean–wheat system, respectively. Among the nutrient supply options, application of 50% RDF + 50% RDN through FYM accounted for highest energy output (286.1 MJ ha-1), net energy (240.3 MJ ha-1) and energy output efficiency (968 MJ ha-1 day-1) and also reduced the C flux to the atmosphere as compared to 100% RDF. Interpretation: The cropping system followed and sources of nutrient supply had considerable impact on utilization of energy as well as carbon emission equivalents. Therefore, besides looking only upon productivity of a particular cropping system and management level, their relative energy efficiency and resultant impact on environment should also be taken into consideration for ensuring judicious use of non-renewable resources.Not Availabl