Dear Friends,
I am facing a problem in quantifying magnetite in a complex natural
mixture, using the conventional Rietveld method (in its quantitative
analysis approach). Apparently, the octahedral morphology of (difficult
to grind) magnetite crystals affects itd diffraction pattern.
To my knowledge, as certified in the original paper (JAC 1986, 267-272),
the ubiquitous and highly performing March-Dollase equation, holding for
"any" crystal symmetry, only applies to inequant crystallites (i.e.
crystallites with unequal sides), or, better said, to "effectively rod-
or disk-shaped specimens" (provided that the geometry of the experiments
keeps cylindrical symmetry). Neither octahedral nor cubic (e.g., NaCl)
crystals can be considered "inequant".
So, the question is:
Is there any way do get around this problem (without resorting to
spherical hamonics or to grind the specimen in a WC, SiC or BN mill)?
Thank you for your patience.
Norberto
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