Modulated Structures CIF Dictionary version 1.0

_atom_site_U_Fourier_param_cos

Name

Category: atom_site_U_Fourier_param

Data type: numb (with optional s.u. in parentheses)

Must appear in a looped list containing '_atom_site_U_Fourier_param_id'
Enumeration default: 0.0

Units: A^2^ ( Angstroms squared)

Definition

    	
   The modulation of the atomic thermal parameters is usually
   parameterized by Fourier series. Each term of the series
   commonly adopts two different representations: the sine-cosine
   form,
            U(ij)c cos(2\p k r)+U(ij)s sin(2\p k r);
   and the modulus-argument form,
            |U(ij)| cos(2\p k r+\c);
   where k is the wave vector of the term and r is the atomic
   average position. _atom_site_U_Fourier_param_cos is the cosine
   coefficient [U(ij)c], in angstroms squared, corresponding to
   the Fourier term defined by _atom_site_U_Fourier_atom_site_label
   and _atom_site_U_Fourier_wave_vector_seq_id. *_iso refers to the
   isotropic atomic displacement parameter.