Thank you Carlo and Shelly, I think the warning message is that "rmax is greater than the distance to the most distant atom" . My cluster size I put into ATOMS the last time I ran this is 5.5. The message then says rmax,ratx 5.5000 5.09117. (My experimental data goes to R = 6.) No matter what cluster size I choose I get the same warning with ratx less than rmax by a small amount. I have tried several cluster sizes and always get the same warning. Sincerely, Doug