1. Departament de Ciències Experimentals, Universitat Jaume I, Box 224, 12080 Castelló, Spain, Department of Mathematics, Laboratorio de Simulação Molecular, Universidade Estadual Paulista, Box 473, 17033-360 Bauru, Brazil, and Faculty of Chemistry, University of Wroclaw, 14 F. Joliot-Curie Str., 50−383 Wroclaw, Poland