Category ATOM_SITE_ROT_SPECIAL_FUNC

Name:
'ATOM_SITE_ROT_SPECIAL_FUNC'

Parent category:
MS_GROUP

Definition:

   

      Data items in the ATOM_SITE_ROT_SPECIAL_FUNC category record
      details about the rotational part of the displacive modulation 
      of a rigid group in a modulated structure when it is not described 
      by Fourier series. Special functions are effective in some cases 
      where the modulations are highly anharmonic, since the number of 
      parameters is drastically reduced. However, they are in general
      discontinuous or with discontinuous derivatives and therefore
      these functions describe an ideal situation that never occurs
      in a real modulated crystal. Up to now, only a few types of
      special functions have been used and all of them come from the
      JANA2006 suite of programs (Petricek, Dusek & Palatinus, 2014). 
      Although this approach is far from being general, it has the 
      advantage that the functions are tightly defined and therefore the 
      atomic displacements and occupations can be calculated easily. In this  
      dictionary, only the special functions available in JANA2006 have been 
      included. 

      These are:

(1) Sawtooth functions for the displacive modulation of atoms and 
rigid groups.
    (2) Zig-Zag functions for the displacive modulation of atoms and
        rigid groups.
    (3) Crenel functions for the occupational modulation of atoms
        and rigid groups. Both of these only apply to
        one-dimensional modulated structures.

      References: Petricek, V., Dusek, M. & Palatinus, L. (2014).
              Z. Kristallogr. 229(5), 345-352.  DOI 10.1515/zkri-2014-1737     
              Crystallographic Computing System JANA2006: General features

              Petricek, V., Eigner, V., Dusek, M. & Cejchan, A. (2016). Z. 
              Kristallogr. 231(5), 301-312. DOI 10.1515/zkri-2015-1913 
              Discontinuous modulation functions and their application for 
              analysis of modulated structures with the computing system JANA2006

Category is of type Loop

Category key:
_atom_site_rot_special_func.atom_site_label