I should have added that Jane's CCSL source code is on: ftp.ill.fr/pub/dif/CCSL (libmk4.tar.gz and maimk4.tar.gz) >Jane Brown's latest version of the CCSL bond lengths and angles routine >does calculate these errors... Alan Hewat, ILL Grenoble, FRANCE <[EMAIL PROTECTED]> tel (33) 4.76.20.72.13 ftp://ftp.ill.fr/pub/dif fax (33) 4.76.20.76.48 http://www.ill.fr/dif/