Density Functional Theory of Metal Carbide Nanocrystals and Surfaces

Details Density Functional Theory of Metal Carbide Nanocrystals and Surfaces Density Functional Theory of Metal Carbide Nanocrystals and Surfaces

Mar 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002aps..marq23011l&link_type=abstract

American Physical Society, Annual APS March Meeting, March 18 - 22, 2002 Indiana Convention Center; Indianapolis, Indiana Meetin

Physics

Condensed Matter

Materials Science

Scientific paper

Transition-metal carbide nanocrystals were first made in the laboratory in the mid 1990’s using laser-vaporization molecular-beam techniques. Even though they contain as few as eight atoms, these particles are found to condense as nanoscopic crystals, as if they were fragments of the corre-spond-ing bulk material. Recently, a new spectroscopic technique called IR-REMPI has been able to measure, for the first time, the infrared (IR) spectra of this family of nanoparticles. These experiments reveal a wealth of surprising results in the composition- and size-dependence of the bonding and vibrational properties of these crystallites. The research we will present focuses on providing theoretical understanding for these new experiments. Using first-principles total-energy methods based on density-functional theory (DFT), we have analyzed the structural and dynamical properties of metal-carbide nanocrystals for various particle sizes and metal species. Since most (and in some cases all) of the atoms in these crystallites reside at the surface, we have also studied the relevant surfaces of the corresponding bulk materials. This comparison has allowed us, for example, to illuminate the connection between measured IR spectral features and bulk surface phonons and to understand the observed size-independence of these features. In addition, our research has been able to explain the observed instability of “corner carbons” in the metal-carbide nanocrystals. Finally, we have examined the emergence of new spectral peaks as a function of particle size at small sizes. In this talk, we will present our research contributions in this area and will also discuss the implications of this work to such diverse disciplines as materials science and stellar astrophysics.

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