(779j) Using Reactive Force Fields to Model Adatom Domains in Fluorinated Graphenes

In the last decade graphene has been studied intensively due to its high electrical conductivity, strength, and elasticity.   In application graphene suffers as it is a zero band gap semiconductor and is weak chemically interactions. Surface chemical functionalization is one method to modify the properties of graphene such that it could be used in transformative technologies.  Fluorine has been a common choice, for examining the effects of surface functionalization on mechanical and electrical properties of graphene.  Experimental observation has shown that graphene can have domains with what appears to be highly ordered fluorine adsorption.  Though the mechanisms by which ordered domain formation happens are not fully understood.

To date, (ReaxFF based) fluorocarbon reactive forcefields have been produced using sets of small fluorocarbon molecules.  While this technique been used with some success in describing fluorinated graphitic materials, it has failed  to reproduce some of the mechanical and dynamic properties seen in higher levels of theory.  Fluorinated graphene structures produced using density functional theory (DFT) and reported previously in references [1-3] were used to refine the force field parameters and to show that they better reproduces the mechanical and dynamical properties of fluorinated graphitic materials.

The new forcefield parameters are applied to a combination of climbing-image nudged elastic band (CI-NEB), molecular dynamics, and parallel replica dynamics (PRD) calculations to study the how fluorine domains form and what occurs at domain boundaries.  We will discuss our latest results and what they may mean for producing stable, high quality fluorographenes for use in technological applications.

1. Jeremy T. Robinson, James S. Burgess, Chad E. Junkermeier, Stefan C. Badescu, Thomas L. Reinecke, F. Keith Perkins, Maxim K. Zalalutdniov, Jeffrey W. Baldwin, James C. Culbertson, Paul E. Sheehan and Eric S. Snow. “Properties of Fluorinated Graphene Films” Nano Lett., 10:3001-3005 (2010)
2. Maxim Zalalutdinov, Jeremy T. Robinson, Chad E. Junkermeier, Jim Culbertson, Thomas L. Reinecke, Rory Stine, Paul E. Sheehan, Brian H. Houston, and Eric S. Snow. “Engineering Graphene Mechanical Systems” Nano Lett. 12:4212-4218 (2012)
3. Chad E. Junkermeier, Stefan C. Badescue, and Thomas L. Reinecke. “Highly Fluorinated Graphene” (arXiv preprint arXiv:1302.6878