**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_phase is the phase (\c/2\p), in cycles, of the complex amplitude corresponding to the Fourier term defined by _atom_site_U_Fourier_atom_site_label, _atom_site_U_Fourier_tens_elem and _atom_site_U_Fourier_wave_vector_seq_id.

Appears in list containing _atom_site_U_Fourier_param_id

The permitted range is -1.0 -> 1.0

Enumeration default: 0.0

**Type:** numb

**Category:** atom_site_U_Fourier_param

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