Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)

français


Accueil > La Recherche > Axes & Equipes > Nanostructures & Spectroscopies > Equipe : Nanomatériaux > Thème : Dopage, confinement et fonctionnalisation dans les nanotubes

Modeling of adsorption in/on carbon nanostructures (and beyond them).

par Sébastien LAYSSAC - publié le , mis à jour le

Introduction.

During the last half of century computational physics has grown in scope and importance to a point where it became a third part of the traditional division between experimental and theoretical physics. Computer simulations second the real experiment and bring an additional insight, at the microscopic level, into the behavior exhibited by complex systems, comprised of thousands to millions of atoms and with large numbers of degrees of freedom. Currently, the computation research program of the group focus on surface physics and adsorption-related phenomena, with three major topics :

1. Modeling of adsorption in confined geometries and on heterogeneous substrates.

The adsorption mechanism in nanoporous materials is very sensitive to intricate local and global pore geometries, which include the possible heterogeneity of the adsorbing surface, pore size distributions, heterogeneous modulation of the pore size along the pore axis, and/or pores interconnectivity. Usually, experimental adsorption isotherms are used to characterize the adsorbing (macroscopic) materials and to deduce information about the microscopic parameters. This interpretation is not always unique because the observed isotherms, of apparently similar forms, may result from very different particular microscopic adsorption mechanisms. In such cases, only appropriate theoretical models can enhance our understanding of those mechanisms.

Heterogeneous adsorbing surface : a 3-site lattice model - © L2C

Recent publication : Langmuir 24, 2008, pp.4013-4019

2. Modeling of optimal sorbents for hydrogen, natural gas and green house gases.

Practical implementation of hydrogen fuel in automotive applications is still impeded by the lack of efficient, economical, light and save storage medium. Even the best candidates, nanoporous activated carbons, hardly meet the targets based on the requirement of 500 km vehicle autonomy and operating pressure below 100 bar at ambient temperatures. Although the specific surface area accessible for hydrogen may be considerably increased by adequate engineering of nanospace, the low heat of hydrogen physisorption on graphite still prevents high storage to be achieved.

Energy landscape for hydrogen adsorption on graphene substituted by 5% of boron - © L2C

Recent publication : Adsorption 15, 2009, pp.312-317

3. Towards simulations of biological systems.

The quality of the results of computer simulations of any real system depends on the quality of force fields of the theoretical model. This becomes critically important when modeling large systems of flexible molecules, such as polymers and biomolecules (especially proteins or lipids). In such systems, correlations between internal and external degrees of freedom determine the local conformational stability of molecules (i.e. folding). Conversely, the same correlations affect intermolecular correlated processes (e.g. phase transitions). Being able to correctly account for the energy and ordering of conformations is essential if force field methods are to be considered as predictive.

Mice amelogenin : secondary structure - © L2C

Recent publication : Langmuir24, 2008, pp.12392-12397


AIGLe

MathJax