3,659 research outputs found
Electronic and total energy properties of ternary and quaternary semiconductor compounds, alloys, and superlattices: Theoretical study of Cu/graphite bonding
The goals of the research were to provide a fundamental science basis for why the bonding of Cu to graphite is weak, to critically evaluate the previous analysis of the wetting studies with particular regard to the values used for the surface energies of Cu and graphite, and to make recommendations for future experiments or other studies which could advance the understanding and solution of this technological problem. First principles electronic structure calculations were used to study the problem. These are based on density functional theory in the local density approximation and the use of the linear muffin-tin orbital band structure method. Calculations were performed for graphite monolayers, single crystal graphite with the hexagonal AB stacking, bulk Cu, Cu(111) surface, and Cu/graphite superlattices. The study is limited to the basal plane of graphite because this is the graphite plane exposed to Cu and graphite surface energies and combined with the measured contact angles to evaluate the experimental adhesion energy
Band structure analysis of the conduction-band mass anisotropy in 6H and 4H SiC
The band structures of 6H and 4H SiC calculated by means of the FP-LMTO
method are used to determine the effective mass tensors for their
conduction-band minima. The results are shown to be consistent with recent
optically detected cyclotron resonance measurements and predict an unusual band
filling dependence for 6H-SiC.Comment: 5 pages including 4 postscript figures incorporated with epsfig figs.
available as part 2: sicfig.uu self-extracting file to appear in Phys. Rev.
B: Aug. 15 (Rapid Communications
Lattice polarization effects on the screened Coulomb interaction of the GW approximation
In polar insulators where longitudinal and transverse optical phonon modes
differ substantially, the electron-phonon coupling affects the energy-band
structure primarily through the long-range Fr\"ohlich contribution to the Fan
term. This diagram has the same structure as the self-energy where
originates from the electron part of the screened coulomb interaction. The two
can be conveniently combined by combining electron and lattice contributions to
the polarizability. Both contributions are nonanalytic at the origin, and
diverge as so that the predominant contribution comes from a small
region around . Here we adopt a simple estimate for the Fr\"ohlich
contribution by assuming that the entire phonon part can be attributed to a
small volume of near . We estimate the magnitude for
from a generalized Lyddane-Sachs-Teller relation,
and the radius from the inverse of the polaron length scale. The gap correction
is shown to agree with Fr\"ohlich's simple estimate of
the polaron effect
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