Porteur de projet :

Mathias Rapacioli ()
LCPQ (MAD)

Laboratoires / Groupes / Equipes partenaires :

LCAR (LPT)

CEMES (MC2)

Années (début–fin) : 2012 - 2015

Abstract

The aim of the present proposal is to reinforce the modeling activity and to establish a collaborative software platform between three teams of NEXT, involved in extensive molecular dynamics simulations or realistic statistical physic investigations of complex systems or processes. Various applications are covered among which (i) the defects and dislocations in materials; (ii) atomic scattering from surfaces leading to adsorption, absorption, surface reconstruction and reactions; (iii) the spectroscopy and reactivity of small and large molecules at the surface of grains or in matrix/cluster environment. In all these cases one common need is to achieve both a local description (defect, dislocation, ad- or ab-sorbate) and a global description of the surrounding environment. For such systems, Density Functional Theory (DFT) is a method of choice. Nevertheless, DFT remains limited to systems of less than a few hundreds of atoms and is furthermore too time-consuming for extensive on-the-fly molecular dynamics or Monte-Carlo simulations. A highly attractive approach to extensive simulations is the Density Functional based Tight Binding method (DFTB), an intermediate approach between first-principles and classical force fields, conserving the same quantum features (orbitals) as DFT and allowing the treatment of reactivity. The aim of the present proposal is to extend the DFTB simulation package in the context of dynamical simulations for condensed matter, large molecular systems and complexes, or for atoms and molecule interactions with surfaces or molecules in matrices.

We will first focus on methodological developments:

• Development of a DFTB version of the code in both periodic and finite systems versions.
• Implementation of a density matrix formulation with sparse matrix techniques in order to accelerate DFTB.
• Coupling of DFTB with the quantum path integral method to go beyond classical molecular dynamics.

The second objective of this proposal relies on sound applications selected among the involved teams, covering various topics and goals like:

• Reactivity of molecules on surfaces such as aromatic molecules and complexes deposited on water ice surfaces or pollutant molecules interacting with soils.
• Metallic systems: investigate the physics of dislocations in materials and the magnetic bimetallic nanoparticles.
• Reactive collisions of atoms with metal surfaces: understand the surface and subsurface dynamics of hydrogen and deuterium atoms impinging on the surface