On Sun, 9 Mar 2008, Alan Hewat wrote:
Precision of CW neutron machines is
frequently not so high as X-ray diffractometers, but this problem is
masked in Rietveld by extremely (artficialy) low e.s.d.'s of lattice
parameters.
Hmm?? With CW neutron machines, the wavelength is sometimes not well
defined so there may be a scale error in the refined lattice parameters.
Lattice dimensions are then precise but not accurate
OK, THIS IS MY MISTAKE, YOU ARE RIGHT.
until they have been
corrected for this scale error. But that has nothing to do with the
accuracy with which the atom coordinates are determined.
IT HAS NOT IF YOU THINK OF FRACTIONAL COORDINATES. IN THE LAST STEP YOU
SHOULD, HOWEVER, TRANSFORM THEM TO CARTESIAN AND THE ACCURACY OF
THE TRANSFORMED VALUE WILL BE TOUCHED BY THE ACCURACY OF THE LATTICE
PARAMETERS.
YOURS,
LUBO SMRCOK
