the semiempirical AM1 (37) method and ab initio DFT with the functional of Perdew, Burke, and Ernzerhof (38., Cohen, M. L., Louie, S. G. & Zettl, A. (1995) Science 269, 966�967. 33. Feldman, Y., Wasserman, E. J. P. (1985) J. Am. Chem. Soc. 107, 3902�3909. 38. Perdew, J. P., Burke, K. & Ernzerhof, M. (1996