radical AM1 geometry optimization



 Dear CCL,
         I would like to know which is the best method to optimize radicals
 (C; N; O) using AM1 as implemented in MOPAC. In  particular, is it better to
 use UHF or open-shell RHF approximation  to obtain a good geometry?
         Any literature reference is appreciated.
         Thank you in advances,
 Eugenia Migliavacca
 Institut de Chimie Thérapeutique
 BEP
 CH-1015 Dorigny-Lausanne
 Tèl.: +41.21.6924529
 E-mail: Eugenia.Migliavacca { *at * } ict.unil.ch