ON THE USE OF COMMON EFFECTIVE CORE POTENTIALS IN DENSITY-FUNCTIONAL CALCULATIONS .1. TEST CALCULATIONS ON TRANSITION-METAL CARBONYLS

The performance of effective core potentials adjusted at the Hartree-F ock level but applied in density functional calculations has been test ed in a set of calculations using various basis sets and/or core poten tials. Test molecules have been the first-row transition-metal carbony ls Cr(CO)(6), Fe(CO)(5), and Ni(CO)(4) and the second-row carbonyls Mo (CO)(6), Ru(CO)(5), and Pd(CO)(4). Only ''small-core'' potentials have been used, and these are able to reproduce molecular structures and b ond energies from all-electron calculations. Relativistic effects have been estimated for the second-row carbonyls by using quasi-relativist ic core potentials. (C) 1996 John Wiley & Sons, Inc.