Its worth noting from the FAQ; http://216.239.59.104/search?q=cache:9uOkOpb4tg0J:www.chem.colostate.edu/mmac/uff.html+uff.html+force+field&hl=en&ct=clnk&cd=2&client=safari that UFF does not apparently deal with hydrogen bonding (having no term for it, and not using partial charges). Ghemical should make this quite clear to the user -- 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).