Step 7 - Analyse the Structure

We’ll introduce another analysis module, Angle, to finish off this tutorial. Angle is similar to DAngle, but is more flexible, assumes less about the connectivity between the sites, and gives more comprehensive output. We’ll use it to calculate the Si–O–Si angle, and the correlations of that angle with the individual Si–O bonds.

Create an empty layer, and add a Angle module to it.

Layer ⇨ Create ⇨ Empty

Show the module palette for the layer by clicking the Show Available Modules button at the foot of the module list at the bottom left of the window

Drag a Angle module from the Analysis group in the Module Palette into the list above to add it to the layer

Now let’s set it up.

Select the Angle module to display its Options

Change the RangeAB Min and Max values to 1.2 and 2.1 respectively, and corresponding to the range of the Si–O bonds

Change the RangeBC Min and Max values to 1.2 and 2.1 as well

Change the AngleRange BinWidth to 5.0

Select the Si site for SiteA and SiteC

Select the O site for SiteB

Enable the ExcludeSameSiteAC option, as otherwise we’ll get a spike at zero in the resulting angle data

Now we can start Dissolve running again and look at the calculated data:

Ctrl-R

Select the Angle module and open the Output page

The three graphs on the first page of Angles tabs shows the two radial distribution functions A–B and B–C, and the A–B–C angle. The RDFs should mirror those calculated by the NeutronSQ module (peak at around 1.6 Å) while the normalised angle graph tells us that all the Si–O–Si angles are predominantly greater than 120°.

The second and third tabs display us the distance-angle correlation graphs, which are both identical in the present case.

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