Modulation parameters

• Step 1:

Description of the modulation

_refine_ls_modulation_function: Types of modulation present in the structural model and their parameterization

Method used for the calculation of the structure factors

_refine_ls_F_calc_details: Details concerning the evaluation of the structure factor.

Wave vectors, used in the modulation functions:

the number of the wave vectors of the Fourier terms used in the structural model to describe the displacive modulation

Measured wave vectors:

the number of the independent modulation wave vectors q_i With them the diffraction vectors are indexed in the form: ha^* + kb^* + lc^* + sum_i (m_iq_i), where sum_i is taken over all wave vectors.

For each one of the atom sites there is a table with the possible modulations and the corresponding function which describes them. You have to choose the type of the modulation by clicking over the corresponding check box and select the modulation function from the list provided. For the description of the functions from which you can select the one used to describe the modulation, please see the "User's Guide" of the computing system "JANA", version February 1993 or version October 1994.
• Step 2:

Measured wave vectors:

the coordinates for the independent modulation wave vectors q_i

Wave vectors, used in the modulation functions:

the coordinates for the wave vectors of the Fourier terms used in the structural model to describe the displacive modulation. Each vector has an unique identificator which can not be changed and will be used when describing the modulation of a given atom site.

Atom sites modulation

for each one of the atom sites and for each one of its modulations the values of the parameters, corresponding to the modulation function have to be given.