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Nano-object Simulation

Head of the team: Christian Angelié/Jean-Maïk Soudan

The general objective is to give a realistic numerical basis to fundamental concepts such as phase transition, chemical segregation and auto organization in Iron/Carbon systems, in relation with the CNT growth on iron catalysts. Novel algorithms and home-made codes are developed to treat of clusters carrying up to a few thousands of atoms. This work develops along two lines:

 

  1. Development of flat histogram MC methods in the spirit of the Wang-Landau (WL) algorithm. A novel algorithm, called « σ-mapping » was introduced by this team. It improves tremendously the convergence of the WL method in regions of phase transitions. It is currently under amelioration to get realistic density of states g(E) for clusters carrying up to 4000 atoms, from which all thermodynamic quantities will be derived.
  2. Development of reactive potential in the spirit of the MEAM potential. MEAM was chosen since it offers a good description of the Fe+C system, still being computationally manageable. Simpler, although accurate,  variant of MEAM are developed to be combined with the MEAM reference within Nested Potential MC algorithm  in order to improve further the computational efficiency.  Further improvement of the potential are currently under progress, especially by including the iron magnetism, for reproducing correctly the full sequence of iron phase transitions α-γ-δ-melting.
 

This research direction was launched thanks to the CEA national programs, CHIMTRONIC and NANOSIMUL.