1,919 research outputs found
A Tight-Binding Investigation of the NaxCoO2 Fermi Surface
We perform an orthogonal basis tight binding fit to an LAPW calculation of
paramagnetic NaCoO for several dopings. The optimal position of the
apical oxygen at each doping is resolved, revealing a non-trivial dependence of
the band structure and Fermi surface on oxygen height. We find that the small
e hole pockets are preserved throughout all investigated dopings and
discuss some possible reasons for the lack of experimental evidence for these
Fermi sheets
Precise Tight-binding Description of the Band Structure of MgB2
We present a careful recasting of first-principles band structure
calculations for MgB2 in a non-orthogonal sp-tight-binding (TB) basis. Our TB
results almost exactly reproduce our full potential linearized augmented plane
wave results for the energy bands, the densities of states and the total
energies. Our procedure generates transferable Slater-Koster parameters which
should be useful for other studies of this important material.Comment: REVTEX, 2 Encapsulated PostScript Figure
Late Glacial–Holocene climatic transition record at the Argentinian Andean piedmont between 33 and 34° S
The Arroyo La Estacada (~ 33°28' S,
69°02' W), eastern Andean piedmont of Argentina, cuts
through an extensive piedmont aggradational unit composed of a dominant Late
Pleistocene–early Holocene (LP–EH) alluvial sequence that includes several
paleosols.
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One of these paleosols developed affecting the topmost part of likely
Late Glacial aeolian deposits aggraded into a floodplain environment by the
end of the Late Pleistocene. The paleosol shows variable grade of
development along the arroyo outcrops. Organic matter humification,
carbonate accumulation and redox processes were the dominant processes
associated with paleosol formation. By the early Holocene, when the
formation of the paleosol ended, renewed alluvial aggradation and high
magnitude flooding events affected the arroyo's floodplain environment. Accordignly,
a period of relative landscape stability in the Arroyo La Estacada basin is
inferred from the paleosol developed by the LP–EH transition in response to
the climatic conditions in the Andes cordillera piedmont after the
Late Glacial arid conditions. The analyzed Late Glacial–Holocene alluvial record of the Andean
piedmont constitutes a suitable record of the LP–EH climatic transition in
the extra-Andean region of Argentina. It is in agreement with regional
paleoclimatic evidence along the southern tip of the South American
continent, where other pedosedimentary sequences record similar late
Quaternary paleoenvironmental changes over both fluvial and interfluvial
areas
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