Advanced initial-guess algorithm for self-consistent-field calculations on organometallic systems

Based upon ligand-field theory, an algorithm to create high-quality initial-guess wavefunctions for organometallic systems leads to the ground state 88% of the time for HF and 92% for DFT. In contrast, calculations starting from a Huckel guess were successful only 14% and 9% of the time, and a traditional AO overlap guess only 39% and 42%. The SCF convergence is also achieved in fewer iteration starting from the advanced guess (on average, in 9 iterations). When several states lie very close in energy, the algorithm also warns the user, making it easy to explore each one. (C) 1999 Elsevier Science B.V. All rights reserved.