These references may be useful as the answers to both "why" and "how". http://pubweb.bnl.gov/users/frenkel/www/PTRU/ptru.pdf http://pubweb.bnl.gov/users/frenkel/www/PTRU/evolution.pdf By "average", do you mean average betwee the A-B and A-A first nearest neighbor coordination numbers? They should not be averaged unless A and B are similar elements, like Cu and Ni. If they have good Z-contrast, EXAFS can count them separately, see refs above. Anatoly -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov]On Behalf Of Juan Antonio Macia Agullo Sent: Thursday, November 23, 2006 1:16 PM To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Coordination number Hi all, I have a simple question but I am afraid it is polemic. Why people always calculate coordination numbers and bond distances and how? I have an e-mail where Bruce described perfectly how to calculate the coordiantion number for the first shell. But,...if I have bimetallic catalysts or/and a mixture of structures with several close paths (similar Reff), then coordination number is an average number? I am not very sure how to calculate them in Artemis with SO2 and standards. Thank you very much Best regards, JA