Profile Parameters Refinement Dialog
Preferred Orientation
Only two preferred orientation functions are currently implemented in the Fullprof program:
Exponential function:
where and
are refinable parameters and
is the acute angle between the scattering
vector and the normal to the crystallites (platy habit). Note that setting
to any number >99.0 for a phase causes the
program to generate, for that phase, only those reflections for which
is parallel to the preferred orientation
vector.
Modified March's function:
where and
are refinable parameters. This expression is
adapted to both fibber and platy habits:
:
Platy habit (
is the acute angle between the scattering
vector and the normal to the crystallites).
:
No preferred orientation.
:
Needle-like habit (
is the acute angle between the scattering
vector and the fibber axis direction)
Note that
these values of correspond to the Bragg-Brentano geometry of
usual X-ray powder diffractometers; for the Debye-Scherrer geometry of most
neutron powder diffractometers the opposite holds.
The
parameter represents the fraction of the sample that is
not textured. The program put its value between 0 and 1 in case of divergence.
Preferred Orientation vector [PREF]
Preferred orientation direction in reciprocal space.