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#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = ["bornagain>=25,<26"]
# ///
"""
Off-specular simulation showing a prominent Yoneda peak.
Sample: vacuum V | mixed M | substrate S.
Layer M contains a polydisperse 2D random assembly of cylindrical
particles P in vacuum.
Critical angle between vacuum and layer M: 2 deg.
The refractive index of substrate S equals the effective medium
index of layer M (linear mixing rule) so that we get no reflection
from the M/S interface. This leaves the V/M Yoneda peak as the
dominant feature.
"""
import bornagain as ba
ba.require_versions("bornagain>=25,<26")
from bornagain import deg, nm
# Target critical angle V->M: alpha_c = 2 deg
# delta_eff = alpha_c**2 / 2 = (2*pi/180)**2 / 2 = 6.09e-4
# Ambient = vacuum (delta_A=0); linear mixing at f=0.5:
# delta_eff = f*delta_P => delta_P = 2*delta_eff
DELTA_P = 1.218e-3 # 2*DELTA_EFF
DELTA_EFF = 0.5*DELTA_P # = 6.09e-4
H = 3*nm # layer thickness = cylinder height
def get_sample():
particle_mat = ba.RefractiveMaterial("Particle", (0.86, 0.24, 0.18),
DELTA_P, 0)
substrate_mat = ba.RefractiveMaterial("Substrate", (0.28, 0.57, 0.82),
DELTA_EFF, 0)
# R = 5±1 nm cylinders, H=2 nm; polydispersity smears F(q_z) oscillations
vacuum_layer = ba.Layer(ba.Vacuum())
mixed_layer = ba.Layer(ba.Vacuum(), H)
ff = ba.Cylinder(5*nm, H)
particle = ba.Particle(particle_mat, ff)
mixed_layer.deposit2D(ba.Dense2D(0.006, particle))
substrate_layer = ba.Layer(substrate_mat)
sample = ba.Sample()
sample.addLayer(vacuum_layer)
sample.addLayer(mixed_layer)
sample.addLayer(substrate_layer)
return sample
def get_simulation(sample):
nscan = 200
scan = ba.AlphaScan(nscan, 1.6*deg, 3.4*deg)
scan.setIntensity(1e8)
scan.setWavelength(0.1*nm)
detector = ba.OffspecDetector(nscan, 1.6*deg, 3.4*deg, -.2*deg, +.2*deg)
return ba.OffspecSimulation(scan, sample, detector)
if __name__ == '__main__':
sample = get_sample()
simulation = get_simulation(sample)
result = simulation.simulate()
ba.showSample3D(sample, sample_size=200*nm, seed=0)
ba.plot_datafield(result)
ba.plt.show()
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