Index

Modulated structures dictionary (msCIF) version 3.2.1

_atom_site_displace_special_func.sawtooth

Definition:

   

   _atom_site_displace_special_func_sawtooth_ items are the
   adjustable parameters of a sawtooth function.
   A displacive sawtooth function along the internal space is
   defined as follows:
         [ux, uy, uz] = 2* [ax, ay, az] * ((x4-c)/w)

   for x4 belonging to the interval [c-(w/2), c+(w/2)], where ax,
   ay and az are the amplitudes (maximum displacements)
   along each crystallographic axis, w is its width, x4 is the
   internal coordinate and c is the centre of the function in
   internal space. ux, uy and uz must be expressed in relative
   units or in angstroms if the modulations are referred to some
   special axes defined by the items belonging to the ATOM_SITES_AXES 
   category, through _atom_site_displace_special_funcs.matrix_seq_id.

   The use of this function is restricted to
   one-dimensional modulated structures. For more details, see
   the manual for JANA2006 (Petricek, Dusek & Palatinus, 2014) and
   (Petricek, Eigner, Dusek & Cejchan, 2016). In the case of rigid groups,
   items in this 
      category would only include the translational part of the modulation. 
      The rotational part would appear in a separate list of items belonging 
      to the ATOM_SITE_ROT_SPECIAL_FUNC category.

      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

Type: Real

Values appear in Matrix context.

Dimension: [3]

Evaluation method:

      With  f  as  atom_site_displace_special_func

      _atom_site_displace_special_func.sawtooth =  [
          
         2 * [f.sawtooth_ax, f.sawtooth_ay, f.sawtooth_az] * 
                     (( f.sawtooth_x4 - f.sawtooth_c) / f.sawtooth_w )]

Category:
atom_site_displace_special_func