Bob I worked through all of the various operators used in the programs I have (including Topas) and they are equivalent in each case. Topas works for this one just as well as GSAS.
Pam Dr Pamela Whitfield CChem MRSC Energy Materials Group Institute for Chemical Process and Environmental Technology Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998 8462 Fax: (613) 991 2384 Email: <mailto:[EMAIL PROTECTED]> ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca -----Original Message----- From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED] Sent: October 18, 2004 4:39 PM To: [EMAIL PROTECTED] Alan, One of your operators is a typo. "-x+y, y, -z+1/3" should be " Y-X Y 1/3-Z" Bob ________________________________ From: alan coelho [mailto:[EMAIL PROTECTED] Sent: Mon 10/18/2004 3:16 PM To: [EMAIL PROTECTED] Pam, As a developer and someone who uses other software to test against, I have been following the discussion with interest. This is a complex area and it goes to show the importance of having a few programs if only for testing purposes. I am puzzled by your cif data however as I cant get past verifying the equivalence of the number of equivalent positions for the Li site. In R-3m you have as fractional atomic coordinates for Li1: x = 0 y = 0.5 and z = 0 For P3112 you have three Li sites with x, y, z's as 0.77780 0.22220 0.83330 0.11110 0.88890 0.83330 0.44440 0.55560 0.83330 which translates to: 0.77780 0.22220 5/6 0.11110 0.88890 5/6 0.44440 0.55560 5/6 Listed below are equivalent positions for a general site. What I dont understand is that for R-3m I get 9 non-overlapping fully occupied equivalent positions within the unit cell with a volume of 101.2975. For P3112 I get 18 non-overlapping equivalent positions with a volume three times as large of 303.8968. I was expecting to get 27 if the two structure were to be equivalent. Thus, from your cif data I am left to conclude that I am generating the wrong number of equivalent positions, or, if I am generating the correct number of equivalent positions then the two cif data sets should indeed give different powder patterns. Have you checked what the number of non-overlapping fully occupied equivalent positions for Li should be for the two structures. alan P3112 xyzs { -x+y, -x, z-1/3 -x+y, y, -z+1/3 -y, -x, -z-1/3 -y, x-y, z+1/3 x, y, z x, x-y, -z } 6 R-3m xyzs { -x, -x+y, -z -x, -y, -z -x+y, -x, z -x+y, y, z -y, -x, z -y, x-y, z y, -x+y, -z y, x, -z x-y, -y, -z x-y, x, -z x, y, z x, x-y, z ' +(-1/3, 1/3, 1/3) ------------------------- -x-1/3, -x+y+1/3, -z+1/3 -x-1/3, -y+1/3, -z+1/3 -x+y-1/3, -x+1/3, z+1/3 -x+y-1/3, y+1/3, z+1/3 -y-1/3, -x+1/3, z+1/3 -y-1/3, x-y+1/3, z+1/3 y-1/3, -x+y+1/3, -z+1/3 y-1/3, x+1/3, -z+1/3 x-y-1/3, -y+1/3, -z+1/3 x-y-1/3, x+1/3, -z+1/3 x-1/3, y+1/3, z+1/3 x-1/3, x-y+1/3, z+1/3 ' +(1/3, -1/3, -1/3) ------------------------- -x+1/3, -x+y-1/3, -z-1/3 -x+1/3, -y-1/3, -z-1/3 -x+y+1/3, -x-1/3, z-1/3 -x+y+1/3, y-1/3, z-1/3 -y+1/3, -x-1/3, z-1/3 -y+1/3, x-y-1/3, z-1/3 y+1/3, -x+y-1/3, -z-1/3 y+1/3, x-1/3, -z-1/3 x-y+1/3, -y-1/3, -z-1/3 x-y+1/3, x-1/3, -z-1/3 x+1/3, y-1/3, z-1/3 x+1/3, x-y-1/3, z-1/3 } 36 /* Fractional atomic coordinates for for R-3m Li1 0.00000 0.50000 0.00000 0.50000 0.00000 0.00000 0.50000 0.50000 0.00000 0.66667 0.83333 0.33333 0.16667 0.33333 0.33333 0.16667 0.83333 0.33333 0.33333 0.16667 0.66667 0.83333 0.66667 0.66667 0.83333 0.16667 0.66667 */ /* Fractional atomic coordinates for P3112 Li 0.44440 0.22220 0.50000 0.77780 0.22220 0.83333 0.77780 0.55560 0.16667 Li 0.77780 0.88890 0.50000 0.11110 0.88890 0.83333 0.11110 0.22220 0.16667 Li 0.11120 0.55560 0.50000 0.44440 0.55560 0.83333 0.44440 0.88880 0.16667 */
