in my previous post, for the values of the Ryckaert-Bellemans parameters (in kJ/mol) that i calculated dihedral C0 C1 C2 C3 C-C-C-C 3.56686 -1.889076 1.313776 -2.33467 should be: dihedral C0 C1 C2 C3 C-C-C-C 3.56686 -1.889076 0.656888 -2.33467 -David Huang