COMPARISON OF REACTION PATHWAYS CALCULATED BY DIFFERENT ALGORITHMS FOR DISILANE AND WATER TRIMER

There still exists some confusion in the literature concerning the def inition of a minimum energy pathway and the coordinate system in which it is calculated. Here we compare steepest-descent and eigenvector-fo llowing pathways, both with and without a mass-weighted metric. The sy stems studied are disilane and the water trimer, and we employ various basis sets at the SCF level of theory. We find that paths calculated using eigenvector-following and steepest-descent are practically the s ame, at least in terms of the reaction mechanism. We find that for the mass-weighted metric the pathways are similar, although in principle they do not have to be identical. Finally, we verify that the geometri cal symmetry selection rules hold for a pathway mediated by a recently discovered transition state of the disilane system.