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#!/usr/bin/env python3
"""
Custom form factor in DWBA.
"""
import cmath
import bornagain as ba
from bornagain import ba_plot as bp, deg, angstrom, nm
def sinc(x):
if abs(x) == 0:
return 1.
return cmath.sin(x) / x
class CustomFormfactor:
"""
A custom defined form factor.
The particle is a prism of height H,
with a base in form of a Greek cross ("plus" sign) with side length L.
"""
def __init__(self, L, H):
""" arguments and initialization for the formfactor """
# parameters describing the form factor
self.L = L
self.H = H
def formfactor(self, q:'C3'):
""" main scattering function """
qzhH = 0.5 * q.z() * self.H
qxhL = 0.5 * q.x() * self.L
qyhL = 0.5 * q.y() * self.L
return (0.5 * self.H * self.L**2
* cmath.exp(complex(0., 1.) * qzhH) * sinc(qzhH)
* (sinc(0.5 * qyhL) * (sinc(qxhL) - 0.5 * sinc(0.5 * qxhL))
+ sinc(0.5 * qxhL) * sinc(qyhL)))
def spanZ(self, rotation):
""" upper and lower z-positions of a custom shape """
return ba.Span(0, self.H)
def get_sample():
"""
Sample with particles, having a custom formfactor, on a substrate.
"""
# materials
vacuum = ba.RefractiveMaterial("Vacuum", 0, 0)
material_substrate = ba.RefractiveMaterial("Substrate", 6e-6, 2e-8)
material_particle = ba.RefractiveMaterial("Particle", 6e-4, 2e-8)
# collection of particles
ff = CustomFormfactor(20*nm, 15*nm)
particle = ba.Particle(material_particle, ff)
particle_layout = ba.ParticleLayout()
particle_layout.addParticle(particle)
vacuum_layer = ba.Layer(vacuum)
vacuum_layer.addLayout(particle_layout)
substrate_layer = ba.Layer(material_substrate)
""" NOTE:
Slicing of custom formfactor is not possible.
all layers must have number of slices equal to 1.
It is a default situation; otherwise use
```
my_layer.setNumberOfSlices(1)
```
Furthermore, a custom particle should not cross layer boundaries;
that is, the z-span should be within a single layer
"""
# assemble sample
sample = ba.Sample()
sample.addLayer(vacuum_layer)
sample.addLayer(substrate_layer)
return sample
def get_simulation(sample):
beam = ba.Beam(1e9, 1*angstrom, 0.2*deg)
n = 100
det = ba.SphericalDetector(n, -1*deg, 1*deg, n, 0, 2*deg)
simulation = ba.ScatteringSimulation(beam, sample, det)
# Deactivate multithreading:
# Currently BornAgain cannot access the Python interpreter
# from a multi-threaded C++ function
simulation.options().setNumberOfThreads(1)
return simulation
if __name__ == '__main__':
sample = get_sample()
simulation = get_simulation(sample)
result = simulation.simulate()
plotargs = bp.parse_commandline()
bp.plot_datafield(result, **plotargs)
bp.export(**plotargs)
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