Index

Modulated structures dictionary (msCIF) version 3.2.1

_atom_site_rot_special_func.zigzag

Definition:

   

      _atom_site_rot_special_func.zigzag_ items are the
      adjustable parameters of a zigzag function.
      A displacive zigzag function along the internal space is
      defined as follows:

               2*[ax,ay,az]*(x4-c)/w for x4 in [c-(w/2),c+(w/2)]
      [rx,ry,rz] = 
              -2*[ax,ay,az]*(x4-c)/w for x4 in [c+1/2-(w/2),c+1/2+(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. rx, ry and rz must be expressed in degrees.
      Special axes are defined by the items belonging to the ATOM_SITES_AXES 
      category, through _atom_site_rot_special_func.matrix_seq_id.
      The use of this function is restricted to one-dimensional 
      modulated structures. For more details, see (Elcoro et al., 2008; 
      Petricek, Dusek & Palatinus, 2014 and Petricek, Eigner, Dusek 
      & Cejchan, 2016). In the case of rigid groups, items in this 
      category would only include the rotational part of the modulation. 
      The rotational part would appear in a separate list of items belonging 
      to the ATOM_SITE_DISPLACE_SPECIAL_FUNC category.

      References: Luis Elcoro, J.M. Perez-Mato, Karen Friese, Vaclav Petricek,
              Tonci Balic-Zunic & Lars Arnskov Olsen (2008)
              Acta Cryst. B64, 684-701. doi:10.1107/S0108768108031492
              Modular crystals as modulated structures: the case of the 
              lillianite homologous series

              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]

Category:
atom_site_rot_special_func