XRaySQ (Module)

Overview

XRaySQ is responsible for taking a set of previously calculated $S(Q)$ from an SQ module and generating a new set of x-ray-weighted structure factors. The total x-ray-weighted structure factor, $F^{X}(Q)$, is generated through summation of the individual partial x-ray-weighted $S(Q)$. X-ray-weighted partial and total radial distribution functions are also calculated.

The XRaySQ module does not target any configurations itself - the underlying GR module, referenced by the SQ module, dictates the source configuration data.

Description

Basic Theory

The XRaySQ module calculates the Faber-Ziman partial structure factors weighted by the atomic x-ray scattering lengths, such that

$$ S^{X}_{ij}(Q) = b_i(Q) b_j(Q) S_{ij}(Q) $$

where $b_i(Q)$ and $b_j(Q)$ are the Q-dependent form factors of the atom types $i$ and $j$ respectively. In a similar manner, the total x-ray-weighted structure factor is

$$ F^{X}(Q) = \sum^N_{i,j,i \geq j} [2-\delta_{ij}] b_i(Q) b_j(Q) c_i c_j S_{ij}(Q) $$

Depending on the need, $F^{X}(Q)$ may be normalised to an appropriate constant with the Normalisation keyword.

Instrumental Broadening

The application of instrumental broadening is the responsibility of the source SQ module - see its QBroadening keyword.

Options

Targets

Keyword	Arguments	Default	Description
SourceSQs	Module	–	Required Source SQ module from which to take unweighted $S(Q)$.

Form Factors & Normalisation

Keyword	Arguments	Default	Description
FormFactors	XRayFormFactors	WK1995	Atomic form factors to use for weighting
NormaliseTo	NormalisationType	None	Normalisation to apply to the total weighted F(Q). The same normalisation is also applied to supplied reference data following removal (if appropriate) of its own normalisation (see the ReferenceNormalisedTo keyword)

Reference Data

Keyword	Arguments	Default	Description
Reference	Data1DFileAndFormat	–	Format and filename of reference $F(Q)$ data, to be displayed in the GUI alongside calculated data, and made available for other modules to utilise (e.g. EPSR
ReferenceFTDeltaR	double	0.05	Spacing in $r$ to use when generating the Fourier-transform of the $F(Q)$
ReferenceFTQMax	double	–	Maximum Q value to use when Fourier-transforming the reference $F(Q)$ to its $G(r)$
ReferenceFTQMin	double	–	Minimum Q value to use when Fourier-transforming the reference $F(Q)$ to its $G(r)$
ReferenceNormalisedTo	NormalisationType	None	Normalisation which has been applied to the reference data
ReferenceWindowFunction	WindowFunction	Lorch0	Window function to apply when Fourier-transforming reference $F(Q)$ to a reference $g(r)$

Export

Keyword	Arguments	Default	Description
SaveFormFactors	bool	false	Save Q-dependent form factors for each atom type pair
SaveGR	bool	false	Save weighted g(r) and G(r). Separate files are written for each partial between atom types $i$ and $j$, as well as the total.
SaveReference	bool	false	Save the reference data and its Fourier transform
SaveRepresentativeGR	bool	false	Save the representative $G(r)$ obtained from Fourier transform of the calculated $F(Q)$
SaveSQ	bool	false	Save weighted partial and total structure factors. Separate files are written for each partial between atom types $i$ and $j$, as well as the total.