### Syntax

spectra = sw_xray(spectra,Name,Value)

### Description

spectra = sw_xray(spectra,Name,Value) calculates x-ray scattering intensity for non-resonant inelastic x-ray scattering on phonons.

### Input Arguments

spectra
Input structure that contains the displacement-displacement correlation function.

### Name-Value Pair Arguments

'formfact'
If true, the magnetic form factor is included in the spin-spin correlation function calculation. The form factor coefficients are stored in obj.unit_cell.ff(1,:,atomIndex). Default value is false.
'formfactfun'
Function that calculates the magnetic form factor for given $$Q$$ value. value. Default value is @sw_mff, that uses a tabulated coefficients for the form factor calculation. For anisotropic form factors a user defined function can be written that has the following header:
F = formfactfun(atomLabel,Q)


where the parameters are:

• F row vector containing the form factor for every input $$Q$$ value
• atomLabel string, label of the selected magnetic atom
• Q matrix with dimensions of $$[3\times n_Q]$$, where each column contains a $$Q$$ vector in $$Å^{-1}$$ units.
'fid'
Defines whether to provide text output. The default value is determined by the fid preference stored in swpref. The possible values are:
• 0 No text output is generated.
• 1 Text output in the MATLAB Command Window.
• fid File ID provided by the fopen command, the output is written into the opened file stream.

### Output Arguments

spectra
Structure that is same as the input with the following additional fields:
• param Input parameters.
• Sperp $$S_\perp(i_{mode},\mathbf{Q})$$ x-ray scattering cross section, stored in a matrix with dimensions of $$[n_{mode n_{hkl}]$$.