Dear Irvin, You seem to be wanting to put in a special form factor for your D2 molecule. In GSAS special form factors need special element names - these are "QA", "QB", ... Then use this name for the atom "type" for your D2 & put in just one of these. If it failed let me have a look at your .EXP file. Best, Bob Von Dreele
R.B. Von Dreele IPNS Division Argonne National Laboratory Argonne, IL 60439-4814 -----Original Message----- From: Telepeni Irvin [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 28, 2007 8:28 AM To: rietveld_l@ill.fr; rietveld_l@ill.fr Subject: RE: How to add a molecule in GSAS? Hi, I finally managed to find out how to put a D2 molecule in GSAS. Rather than having one D with the double of the scattering length, it was recommended to do as following in the GSAS news(2002 march: I entered the form factor of D2 molecule as a table of sin(theta)/lambda VS form factor (from a .txt file) (expedt: Y + L + F + N + QA + R + U). This option seems only valid for free rotor (CH$ and H2 ...) But while GSAS reads (but does not plot) the new form factor from the file, but it does not recognise the new "atom type" as a standard atom when I try to add the corresponding atom. Have I missed something? Cheers Irvin -----Original Message----- From: AVDEEV, Maxim [mailto:[EMAIL PROTECTED] Sent: Mon 08/10/2007 23:58 To: rietveld_l@ill.fr Subject: RE: How to add a molecule in GSAS? Irvin, With GSAS discrete D2 molecules can be modeled using rigid body constraints: http://www.ccp14.ac.uk/solution/gsas/rigid_bodies_gsas.html http://www.ccp14.ac.uk/ccp/web-mirrors/ian-swainson/fireside_fuide_to_ri gid_bodies.pdf If the molecules are rotationally disordered you might try special form factors (like spherical shell one implemented in Fullprof) http://www.ill.fr/dif/Soft/fp/index.html In the extreme case of disorder you may also try to model continuous distribution of scattering density with Maximum Entropy Method (for example with Rietan+Prima) http://homepage.mac.com/fujioizumi/rietan/angle_dispersive/angle_dispers ive.html Cheers, Max This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.