The techniques of generalized simulated annealing are here presented in a w
ay to fit the external turning points of a diatomic molecule potential ener
gy curve. In order to evaluate the advantages of this method the long-range
part of the potential energy curve for the A(1)Sigma(u)(+) electronic stat
e of the Li-6(2) molecule is treated using the multipolar expansion and the
asymptotic exchange energy considering the gradual change from a Hund's ca
se a towards Hund's case c. The results are carefully compared with previou
s determinations using conventional fitting methods of molecular spectrosco
py. (C) 1999 Elsevier Science B.V. All rights reserved.