BASIS-SETS FOR TRANSITION-METALS - OPTIMIZED OUTER P-FUNCTION

Although the (n + 1)p orbital is unoccupied in transition-metal ground -state configurations which are all nd(x)(n + 1)s(y), these (n + 1)p f unctions play a crucial role in the structure of transition metal comp lexes. As we show here, the usual solution, adding one or more diffuse functions, can be insufficient to create an orbital of the correct en ergy. The major problem appears to be due to the incorrect placement o f the (n + 1)p orbital's node. Even splitting the most diffuse compone nt of the np orbital and adding a second diffuse function does not com pletely solve this problem. Although one can usually solve this defici ency by further uncontracting of the np function, here we offer a set of properly optimized (n + 1)p functions that offer a more compact and satisfactory solution to the proper placements of the node. We show a n example of the common deficiencies seen in typical basis sets, inclu ding standard basis sets in GAUSSIAN94, and show that the new optimize d (n + 1)p function performs well compared to a fully uncontracted bas is set. (C) 1996 by John Wiley & Sons, Inc.