1. Center for Complexity and Biosystems, Department of Physics, University of Milan, Via Celoria 16, 20133 Milano,
Italy
2. Institute of Materials Simulation, Department of Materials Science, Friedrich-Alexander-Universität Erlangen-Nürnberg,
Dr.-Mack-Str. 77, 90762 Fürth, Germany
3. CNR—Consiglio Nazionale delle Ricerche, Istituto di Chimica della Materia Condensata e di Tecnologie per l’Energia, Via R.
Cozzi 53, 20125 Milano, Italy