Analysing X-ray data using GudrunX. Outline. Planning an experiment Absorption Fluorescence Beam size Data required Outline of analysis process Step by step guide through analysis Practice with some data! SiO 2 H 2 O Tellurite glass. Planning an experiment.
If we accept 60% loss offlux, we can estimate the diameter of capillary to use:
H2O : µ = 0.656
ln(0.4)/-6.626 = 1.4 cm
d ~ 1.8 cm
Al2O3 : µ = 6.626
d ~ 2 mm
GeO2: µ = 96.906
d ~ 0.12 mm
Y2O5: µ = 186.756
d ~ 0.07 mm
TeO2 : µ = 68.607
d ~ 0.18 mm
PbO : µ = 549.499
d ~ 0.03 mm
Area = πr2
L =(πr2)/2r = π/4 d
~ 3/4 d
Increase Z → increased energy at which K edge occurs.
for region around Ag
(Z > Ag) µ/ρ < (Z <Ag)
HOWEVER, there is also density to consider
A Material chosen as a β filter must have an absorption edge which lies between the Kα and Kβ peaks.
For an Ag tube, Rh is used.
Anti scatter slit
Prog. Rec. slit
Diameter of sample (L)
Prog. Div. slit
PDS angle (θ)
240 mm (r)
PDS θ (rad) = L/r
ASS= PDS x 2
PRS (mm) = L
Once the experimental setup has been decided up, three measurements are required – as with Neutron analysis, these are:
Sample in capillary
All these measurements need to be taken under the SAME CONDITIONS.
The current set up is to collect data at 0.2° intervals from 3.2 – 156°.
At each point, data is collected of 30 seconds.
There is the option to collect two sets of data:
Several repeat scans from 3.2 to 156°
Additional scans from 35to 156° to improve statistics at high Q
Krogh-Moe – Norman normalisation
Effect of normalisation:
The X-ray diffractometer webpages can be found at
OR as a link from the disordered materials group web page.
User must choose which method of normalisation they wish to apply to the data.
Altering Breit-Dirac factor and Overlap factor can give some improvements to the extracted F(Q). Maintain default values initially.
Select an appropriate sample background panel.
‘Read data’ will display the information from the .XRDML file, including number of scans and the range of angles over which the chosen data set has been measured.
Set sample background factor (between 0.9 and 1)
Composition, container size (inner and outer dimensions), effective density.
For density either the measured effective density can be given, with a tweak factor = 0
Or the bulk density can be used with the tweak factor alteredEffective density = bulk density/tweak factor
Basic information + fluorescence, multiple scattering etc.
Ensure that packing fraction is sensible (measure or estimate it ~60%)
Vary effective density and multiple scattering first, then bremsstrahlung.
Only apply fluorescence for samples containing Rb – Te.
X = 2θ
Y1 = experimental data
Y2 = single atom scattering
Y6 = Bremsstrahlung
X = Q
Y1 = F(Q)
F(Q) will have been normalised to either <f>2 or <f2>. Ensure that you have a record of which you used!
X = r
Y1 = G(r)
Quality of G(r) can be improved by varying parameters in GudrunX. Alternatively, the fourier transform software in Open Genie can be used.
Daniel will be discussing the relationship between various correlation functions
X-ray energy > absorption edge in sample → Fluorescence
Fluorescence provides a background which is uniformly distributed across the angular range
Multiplying the data measured for the empty capillary and Ca/Sr glass data by a scale factor to match the Ca glass data (at high angle) gives:
The shape of the capillary and calcium data are well matched.
Problem with strontium sample.
However, if a constant background is subtracting from the Ca/Sr data and THEN the data is scaling:
The characteristic X-ray shape is onceagain present in the data