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.

 

 

Colour notes