Category: atom_site_U_Fourier
Data type: char
Must appear in a looped list
containing '_atom_site_U_Fourier_id'
Must match a value of '_atom_site_label'
Modulation parameters are usually looped in separate lists. Modulated parameters are the atomic positions (displacive modulation), the atomic occupation (occupational modulation) and/or the atomic anisotropic (or isotropic) displacement parameters (referred to as modulation of thermal parameters since the term 'displacement parameters' is ambiguous in this context). _atom_site_U_Fourier_atom_site_label is the code that identifies an atom in a loop where the Fourier components of its thermal parameters modulation are being listed. This code must match the _atom_site_label of the associated coordinate list and conform to the rules described in _atom_site_label.