I found this SF site which may provide parameters already for all the elements. It also includes typos for UFF which are well worth knowing about! Anyone heard of Marcus Martin? The following http://towhee.sourceforge.net/towhee_capabilities.html has a superb summary of what must represent pretty much all known force fields -- Henry Rzepa. +44 (020) 7594 5774 (Voice); +44 (0870) 132 3747 (eFax); rzepahs at mac.com (iChat) http://www.ch.ic.ac.uk/rzepa/ Dept. Chemistry, Imperial College London, SW7 2AZ, UK. (Voracious anti-spam filter in operation for received email. If expected reply not received, please phone/fax).