1. Department of Physics, Sapienza University of Rome, Rome, Italy
2. Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
3. Department of Physics, University of Illinois Urbana-Champaign, Champaign, llinois 61801, USA
4. Department of Physical and Chemical Sciences, University of L’Aquila, L’Aquila, Italy
5. Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France