555 research outputs found
High-pressure Debye-Waller and Grueneisen parameters of Au and Cu
The lattice vibrations are determined in the quasi-harmonic approximation for
elemental Au and Cu to twice their normal density by first-principles
electronic band-structure calculations. It is found for these materials that
the important moments of the phonon density of states can be obtained to high
accuracy from short-ranged force constant models. We discuss the implications
for the Grueneisen parameters on the basis of calculated phonon moments and
their approximations by using bulk moduli and Debye-Waller factors.Comment: 4 pages, 2 figures to appear in the proceedings of the 13th APS
Topical Conference on Shock Compression of Condensed Matter (scheduled for
April 2004
Automated mass spectrometer/analysis system: A concept
System performs rapid multiple analyses of entire compound classes or individual compounds on small amounts of sample and reagent. Method will allow screening of large populations for metabolic disorders and establishment of effective-but-safe levels of therapeutic drugs in body fluids and tissues
Slabs of stabilized jellium: Quantum-size and self-compression effects
We examine thin films of two simple metals (aluminum and lithium) in the
stabilized jellium model, a modification of the regular jellium model in which
a constant potential is added inside the metal to stabilize the system for a
given background density. We investigate quantum-size effects on the surface
energy and the work function. For a given film thickness we also evaluate the
density yielding energy stability, which is found to be slightly higher than
the equilibrium density of the bulk system and to approach this value in the
limit of thick slabs. A comparison of our self-consistent calculations with the
predictions of the liquid-drop model shows the validity of this model.Comment: 7 pages, 6 figures, to appear in Phys. Rev.
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Simple DFT-LSDA modeling of the molecular-like aspects of ultra-thin film properties
Ordered ultra-thin films (UTF`s) are atomic n-layers (n = 1,2,3,...) with translational symmetry in-plane and molecular-like inter-planar spacings. Though commonly used (especially at relatively large n-values) as models of crystalline surfaces, they are intrinsically interesting and of growing technological significance as the basic building blocks of multi-layer electronic devices. Predicting the structure and properties of even a simple diatomic 1-layer means addressing aspects of molecular binding (and boundary conditions) in the context of an extended, periodically bounded system. At the level of refinement provided by the local spin density approximation to Density Functional Theory, the baseline standard of today`s predictive, chemically specific solid-state calculations, a number of technical and fundamental issues arise. The authors focus on treatment of the isolated atoms, on basis sets, and on numerical precision, as illustrated by the Fe atom and BN 1- and 2-layer calculations. Computational requirements are illustrated by a brief summary of recently completed calculations on crystalline sapphire, {alpha}-Al{sub 2}O{sub 3}, which used the same code
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