Bond angles restraints in GSAS

[Matteo Zoppi]

Dear Rietvelders,

does anyone please let me know if there are some 
mistakes one can do when trying to use both bond 
lengths and angles restraints in GSAS? It is 
probably something trivial. I can't find why, 
when I try to refine a structure (monoclinic or 
triclinic) with bond angles restraints on the 
octahedral positions of oxygen, the bond 
distances restraints work perfectly but bond 
angles restraints don’t. I restraint bond angles 
of oxygen-metal-oxygen to 90(3) with a high FACTR 
but apparently these values are not retained and 
shift to mach smaller of bigger values.
Initial starting values are within the correct 
range, and restraints are put on atoms within 
close bonding distance of each other.
Thank you for your help.
Matteo

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   Dr. Matteo Zoppi
   Museo di Storia Naturale - Sezione di Mineralogia
   Università degli Studi di Firenze
   Via G. La Pira, 4 – 50121 Firenze, ITALY
   Tel. +39 055 2756340
   [EMAIL PROTECTED]
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