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Simulations of Liquids, Aggregates, Semiconductors and Molecular Crystals
Introduction
The study of
the structural and electronic properties of solids, liquids and clusters with
density functional methods has been the main activity of the simulation group.
Many collaborations have been established to study a wide range of materials.
We studied
liquid alloys with first principles molecular dynamics methods, using the
pseudopotential plane-wave code. We were interested on the appearance of short
range order in the alloys, in particular if one atom prefers to be surrounded by
atoms of the same chemical species, or if it prefers to be surrounded by atoms
of a different chemical species. We simulated metallic alloys where these
deviations from randomness were known to occur. We have recently simulated
expanded liquid metals where clustering phenomena are important.
In the past
few years we shifted our interest from less common semiconductor crystals
(nitrides, tellurides, halides) to molecular crystals. Results on cubane, urea,
polyethylene and halogens have been published. Our interest in the molecular
crystals is to study the structural and mechanical properties of these soft
materials. Recently we studied molecular dissociation in nitrogen crystals under
pressure. These are simulated with a plane-wave pseudopotential method. Our
method of variational cell-shape is well adapted to the study of mechanical
properties as it allows the optimization of geometry under strain.
We simulated
charged clusters with the objective to simulate the coulomb explosion
phenomenon. Clusters that are ionized with more than one elementary charge may
fission in several charged fragments. This is observed in experiment, but the
detailed microscopic mechanism is not well known. The experimental information
on the structure of small metalic clusters is scarce and mostly indirect.
Furthermore there are many isomers that are close in energy, so there could be
more than one type of structure for a given cluster, and most of the times the
computational model is not accurate enough to distinguish between isomers. One
property that is sensitive to cluster shape is the polarizability and the
photo-response (they are related by sum rules), hence our interest in
calculating those properties, as comparison of theory to experiment can help
identify which isomer is observed. We recently studied Si cage clusters to check
their stability in condensed phases. For more information on this research topic, contact Prof. José Luís Martins. Main Results
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Copyright © 2010 INESC MN; all rights reserved · Last update: 29 June 2010 · |