1. Department of Solid State Sciences, Ghent University, Krijgslaan 281 S1, 9000 Gent, Belgium
2. Schrödinger Inc., 120 West 45th Street, 17th Floor, New York, New York 10036-4041, United States
3. Department of Physics, University of Jyvaskyla, P.O. Box 35, FI-40014 Jyvaskyla, Finland