Presume one of your students makes a fit on a sample having only size
anisotropy and he is able to determine the six parameters of the ellipsoid.
But after that he has a funny idea to repeat the fit changing (hkl) into
equivalents (h'k'l'). He has a chance to obtain once again a good fit, with
other ellipsoid parameters but with (approximately) the same average size, this
time in other direction
[lamda/cos(theta)/M(hkl)=lamda/cos(theta)/M(h'k'l')]. Am I wrong?
But why to presume so soon that people are dumb ?
You may also presume that the student is not stupid enough for trying to determine the 6 parameters of the ellipsoid in any case and that he applies restrictions related to the symmetry, as recommended in the software manual (the software name was ARIT)... That manual says that the 6 parameters are obtainable only in triclinic symmetry, etc.
I prefer to presume first that people are smart, and may be change my opinion later.
I guess that the Lij in GSAS are explained to be symmetry- restricted as well.
Armel
