This is a simple example of showing the computation of virutal x-ray and electron diffraction patterns for Ni.

In addition to the LAMMPS output, a simple visualizaiton of the electron diffraction data is included. The visualization was created using the VisIt Open Source visualiztion software develeoped at Larrence Livermore National Laboraatory (https://wci.llnl.gov/simulation/computer-codes/visit/).

Below is a step by step guide to produce similar images:

a) Open the diffraction .vtk files in VisIt

b) Click add->pseudocolor->intensity;

*Note, green name means its ready to be drawn

c) Click Draw;

*Note, you will see the full rectangular mesh grid which is what we are wanting.

We need to remove ghost data (those values set to -1).

d) Select intensity plot;

Click Operators->Selection->Isovolume; Double click isovolume (under intensity plot); Change lower bound to 0; Click Apply; Click Dismiss; Click Draw;   *Note, now you will see only where there was valid intensity data (if you don't use Zone it will be a sphere).  But most intensity are low so color the intensity by log scale.

e) Select intensity plot

Double click Pseudocolor; Change Scale to Log; Check Mimimum Limit; Input non-zero minimum limit (i.e. 1); Click Apply; Click Dismiss;

Note, clicking apply will change the scale automatically.  But unless you have used Zone and a thin dR_Ewald you likely have lots of extra data visualized that does not intersect the Ewald sphere.  Next, we want to take a spherical slice to mimic the intersection of Ewald's sphere with reciprocal space.

f) Select intensity plot; Click Operators->Slicing>Spherical Slice; Double click Spherical Slice; Change the origin/radius to represent the center of your Ewald sphere;

**(i.e. 39.84063 0 0) and radius (i.e. 39.84063) for lambda = 0.251 **

Click Apply; Click Dismiss; Click Draw;

This is the saed pattern, but we are not guaranteed to be aligned correctly with the zone axis.

g) On the menu bar... select Controls -> View;

Change View Normal to the zone axis of choice (i.e. -1 0 0); Adjust Up Vector if desired (i.e. 0 1 0); Turn off Perspective view; Click Apply; Click Dismiss;

*Note that for the primary x, y, and z zone axis you can use the drop own Align to axis.  However, it is likely that there is a bunch of extra annotations on the image that don't look appealing.

h) On the menu bar... select Control-> Annotation;

*Here you can change what is visualized along side the data and how you display axis information.  I typically turn most all the display information off.

i) Save the image

Click File-> Set save options Click Save

• Note, further fine tuning can be achieved by adjusing the color table and

max/min values **