Better Band Gaps with Asymptotically Corrected Local Exchange Potentials

We formulate a spin-polarized van Leeuwen and Baerends (vLB) correction to the local density approximation (LDA) exchange potential [Phys. Rev. A 49, 2421 (1994)] that enforces the ionization potential (IP) theorem following Stein et al. [Phys. Rev. Lett. 105, 266802 (2010)]. For electronic-structure problems, the vLB-correction replicates the behavior of exact-exchange potentials, with improved scaling and well-behaved asymptotics, but with the computational cost of semi-local functionals. The vLB+IP corrections produces large improvement in the eigenvalues over that from LDA due to correct asympotic behavior and atomic shell structures, as shown on rare-gas, alkaline-earth, zinc-based oxides, alkali-halides, sulphides, and nitrides. In half-Heusler alloys, this asymptotically-corrected LDA reproduces the spin-polarized properties correctly, including magnetism and half-metallicity. We also considered finite-sized systems [e.g., ringed boron-nitirde (B$_{12}$N$_{12}$) and graphene (C$_{24}$)] to emphasize the wide applicability of the method.Comment: 9 pages, 3 figure

Feasibility of a nuclear gauge for fuel quantity measurement aboard aircraft

Capacitance fuel gauges have served as the basis for fuel quantity indicating systems in aircraft for several decades. However, there have been persistent reports by the airlines that these gauges often give faulty indications due to microbial growth and other contaminants in the fuel tanks. This report describes the results of a feasibility study of using gamma ray attenuation as the basis for measuring fuel quantity in the tanks. Studies with a weak Am-241 59.5-keV radiation source indicate that it is possible to continuously monitor the fuel quantity in the tanks to an accuracy of better than 1 percent. These measurements also indicate that there are easily measurable differences in the physical properties and resultant attenuation characteristics of JP-4, JP-5, and Jet A fuels. The experimental results, along with a suggested source-detector geometrical configuration are described

Validation of Genome-Wide SSR Markers Developed for Genetic Diversity and Population Structure Study in Grain Amaranth (Amaranthus hypochondriacus)

Grain Amaranth is the most promising C4 dicotyledonous pseudocereal and is distributed globally. It has an excellent nutritional profile and adaptability against a broad range of environmental factors. These traits have renewed the interest of researchers and breeders in exploring this underutilized orphan crop. The present study aimed to validate the genome-wide SSR to assess the genetic diversity among 94 Amaranthus hypochondriacus accessions using 57 genomic SSR (g-SSR) markers developed in-house. A total of 36 g-SSRs were recorded as polymorphic and amplified 138 alleles, with an average of 3.83 alleles per locus. Major allele frequency ranged from 0.29 to 0.98, with an average of 0.63 per marker. The expected heterozygosity ranged from 0.03 to 0.81, with an average of 0.46 per locus. Polymorphism information content (PIC) ranged from 0.03 to 0.79, with an average of 0.40, indicating a high level of polymorphism across amaranth accessions. Population structure analysis resulted into two major genetic clusters irrespective of their geographical origin, which suggests there may be sharing of common genomic regions across the accessions. High allelic frequency and heterozygosity levels indicate significant genetic variability in the germplasm, which can be further used in future breeding programs

Piston Core Properties and Disturbance Effects

Laboratory geotechnical data on piston cores from 31 sites on the mid‐Atlantic Upper Continental Slope show the near‐surface sediments vary from normally consolidated to somewhat overconsolidated clayey silts and silty clays of low to high plasticity. They also exhibit normalized behavior and their index property correlations with the effective‐stress friction angle, the undrained strength ratio, and the compression index are reasonably consistent with existing knowledge. Disturbance effects were effectively minimized in the consolidation and strength parameter determinations by using stresses and stress histories in excess of those in situ. However, substantial disturbance effects in preconsolidation stress determinations were found. The preconsolidation stress values derived from the triaxial data are high, and those from the consolidation data are low, compared with the values obtained from the laboratory vane data. Because existing knowledge concerning disturbance effects suggests that in‐situ preconsolidation stress values should lie between those derived from the triaxial and laboratory vane data, the preconsolidation stress values obtained from the consolidation data appear to be appreciably smaller than in‐situ values

Better band gaps with asymptotically corrected local exchange potentials

We formulate a spin-polarized van Leeuwen and Baerends (vLB) correction to the local density approximation (LDA) exchange potential [R. van Leeuwen and E. J. Baerends, Phys. Rev. A 49, 2421 (1994)] that enforces the ionization potential (IP) theorem following T. Stein et al. [Phys. Rev. Lett. 105, 266802 (2010)]. For electronic-structure problems, the vLB correction replicates the behavior of exact-exchange potentials, with improved scaling and well-behaved asymptotics, but with the computational cost of semilocal functionals. The vLB + IP correction produces a large improvement in the eigenvalues over those from the LDA due to correct asymptotic behavior and atomic shell structures, as shown in rare-gas, alkaline-earth, zinc-based oxides, alkali halides, sulfides, and nitrides. In half-Heusler alloys, this asymptotically corrected LDA reproduces the spin-polarized properties correctly, including magnetism and half-metallicity. We also consider finite-sized systems [e.g., ringed boron nitride ( B 12 N 12 ) and graphene ( C 24 )] to emphasize the wide applicability of the method.This article is from Physical Review B 93 (2016): 085204, doi:10.1103/PhysRevB.93.085204. Posted with permission.</p