Density functional calculations with simulated annealing—isomers of S 7 X [X  O, S, Se], Se 8 , O 8

Density functional calculations—with a local density approximation for the exchange and correlation energy—provide a numerically efficient method for determining total energy variations in molecules. Coupled with molecular dynamics techniques such as simulated annealing, they provide a scheme for probing large regions of configuration space in molecules. We outline the main features of the method and apply it to different ring isomers of S 7 O, S 8 , S 7 Se, Se 8 , and O 8 .