Core correlation effects in weak interactions involving transition metal atoms

In our calculations of weak interactions in transition metal complexes some rather unusual contributions due to excitations from relatively inert subv alence electronic shells have been observed for copper interacting with wat er and ammonia. These contributions are analyzed in terms of cluster amplit udes which indicate that the copper-molecule interaction considerably incre ases the near degeneracy of atomic states. The t(1) amplitude associated wi th the 3d --> 4s excitation rapidly increases with the decrease of the copp er-molecule distance. This, in consequence, leads to the increasing role of the 3p shell polarization. This effect is essentially absent in the case o f silver complexes. (C) 2000 American Institute of Physics. [S0021-9606(00) 31601-4].