CosPlay

a coherent scattering playground

Scatterers

Arrangement

x (Å) y (Å) n d (Å) n m a (Å) b (Å) γ (°) N N d_min (Å) d_max (Å) x (Å) y (Å)

(click on the plot to add a scattering centre)

Wave

Interference ON Source plane wave Re-emitted waves Multiple scattering OFF

Spectrum

λ₂ (Å) I₂/I₁ Width (%) Samples

Phases

2D falloff 1/√r Fade at edges

Profile

Display

Show

Scatterers Bragg beams

Colour map Scatterer colour

Scale bar Source direction

Far field

Log scale

Animation

Time-averaged

Scatterer list

Positions x, y in Å, one per line, before the rotation φ

Points in the cell

x, y (Å) Click to place or remove

Spectrum

Values in

Spectrum lines: value and intensity weight, one per line

Load file…

What is this about?

CosPlay shows in animation what crystallography textbooks explain through equations: X-ray diffraction as a sum of waves.

When an X-ray wave hits an electron (scatterer), its energy is absorbed and re-emitted as a spherical wave with the same energy (wavelength) and a phase shift of π/2. When more electrons are present (molecules and crystals), this occurs for each electron, and the sum of all the waves produces what we measure as coherent elastic scattering.

When the spacing between rows of scatterers repeats with a specific d and along a certain direction (both satisfying Bragg's law), the sum of these waves (interference) produces bright beams of intensity: diffraction.

In CosPlay, Bragg's law is not imposed: it emerges spontaneously from a simple sum of emitted waves, whose phases are defined by the scatterers' position inside the field of the source wave.

That's more than enough theory… time to start playing! Can you find the famous “planes” of scatterers when you see a Bragg beam appearing?

Licence

CosPlay is free software: you may use it, study it, pass it on and change it under the GNU General Public License, version 3 or any later version. Anything you build from it must stay free under the same terms.

It is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the licence for the details.

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Resolution Mpixel