Index

Modulated structures dictionary (msCIF) version 3.2.1

_atom_site_Fourier_wave_vector.xyz

Definition:

   

      Wave vectors of the Fourier terms used in the structural model
      to describe the atomic modulation functions, expressed with
      respect to the three-dimensional reciprocal basis that spans
      the lattice of main reflections. They are linear combinations
      with integer coefficients of the independent wave vectors given
      in the _cell_wave_vector. list. Therefore, a generic Fourier wave
      vector is expressed as k=n(1)q(1)+...+n(p)q(p), where p is given
      by _cell_modulation_dimension. In the case of composites
      described in a single data block, these wave vectors are
      expressed with respect to the three-dimensional reciprocal
      basis of each subsystem (see _cell_subsystem.matrix_W_*).

Type: Real

Values appear in Matrix context.

Dimension: [3]

Evaluation method:

       With  m  as  atom_site_Fourier_wave_vector

            atom_site_Fourier_wave_vector.xyz   =   [ m.x, m.y, m.z ]

# The null vector is allowed for a possible homogeneus term of Fourier Series. But
# it is also used as a test for the case where m.x, m.y and m.z are not given and 
# therefore an alternative way to have the wave vectors is necessary

       If (atom_site_Fourier_wave_vector.xyz == [0.0,0.0,0.0] {
       
         Loop w as cell_wave_vector {

           i=0
           For s in m.q_coeff_seq_id {
              If (w.seq_id == s) {

                atom_site_Fourier_wave_vector.xyz_from_coeff =
                atom_site_Fourier_wave_vector.xyz_from_coeff + m.q_coeff[i]*w.xyz }

              Else {

                i += 1 }

           } # End For
         }   # End Loop
       }     # End If

Category:
atom_site_Fourier_wave_vector