Datasqueeze provides a number of pre-defined settings for making plots.
If you click on one of these buttons everything is done for you, with (almost)
no decisions to make.
- Powder Plot
This makes a plot similar to what you could get in a traditional theta-2theta
powder diffraction scan. It is equivalent to setting the Independent/Dependent variables
to Q/Chi, so that we plot versus Q=2 pi / d and integrate over the azimuthal angle.
The scale is set to run from 0.05 to 0.95 of the Q-range.
The increment is set to a round number such that there are something close to
500 points in the plot.
- < Pole Figure Plot
This plots the intensity versus azimuth angle (chi).
It is equivalent to setting the Independent/Dependent variables
to Chi/Q, so that we plot the azimuthal angle and integrate over Q=2 pi / d.
Q is set to average from 0.05 to 0.95 of the Q-range.
Chi runs from 0 to 360 degrees in steps of 2 degrees.
- Guinier Plot
The Guinier law states that in the limit as q goes to zero the scattered intensity is proportional
to exp(-q2 Rg2/3) where Rg is the radius of gyration
of the scattering object. Accordingly, if we plot log10(I) versus q2 the slope can be be
related to the radius of gyration. Clicking the Guinier button is equivalent to
setting the Independent/Dependent variables
to Q^2/Chi, so that we plot versus Q^2 and integrate over the azimuthal angle.
The scale is set to run from Q2= (0.05 * qrange)2 to
Q2= (0.95 * qrange)2.
The increment is set to a round number such that there are something close to
500 points in the plot. A logarithmic scale is used for the Y-Axis.
- Porod Plot
The Porod law states that, for small-angle scattering from isolated objects (spheres, rods, sheets, etc.),
as q becomes large the scattering is proportional to 1/q4. Accordingly, a plot of
q4 I(q) should approach a constant. Clicking the Porod Plot button is similar to
clicking the Powder Plot button except that
n is set to 4 in the
Multiply by X^n box so that we plot q4 I(q).
Note that for most real data this plot will not approach a constant. This can happen
for two reasons. First, there may be real wide-angle scattering due to interparticle correlations.
For example, in a polymer melt there will be wide-angle scattering due to chain-chain correlations.
Second, there may be a background signal due to air scattering, scattering from widows, etc. If this
background is constant it will lead to a rising curve in a Porod plot. If you believe that this is happening
you may wish to play with subtracting a constant number of counts per pixel in the
File Panel.
- Custom Presets
You can save two different settings for user-defined plot parameters. This is useful if you
want to plot a number of different data sets in exactly the same way, even in different multiple
analysis sessions. Suppose, for example, that you want to define "Custom Preset 1." You do this in
the following way:
- Using the other plot controls, set up a plot exactly the way you want it (correct
Dependent/Independent variables, right choice of axis log/linear buttons, right choice of
plot range and increment, etc.).
- Click the "Set C1" button. Datasqueeze will now remember these settings. If you answer
affirmatively to the "save current settings" query when you exit, it will even remember these
settings from one session to the next.
- Now when you click "Custom1 " you will get the same kind of plot even if you have done
other plots in the interim.
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