### Custom formfactor

Scattering from a monodisperse distribution of particles, whose form factor is defined by the user.

• This example shows how users can simulate their own particle shape by implementing the analytical expression of its form factor.
• The particular shape used here is a polyhedron, whose planar cross section is a “plus” shape with a side length of $20$ nm and a height of $15$ nm.
• These particles are distributed on a substrate.
• There is no interference between the scattered waves.
• The wavelength is equal to 0.1 nm.
• The incident angles are $\alpha_i = 0.2 ^{\circ}$ and $\varphi_i = 0^{\circ}$.
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94  #!/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(ba.IFormFactor): """ 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): ba.IFormFactor.__init__(self) # parameters describing the form factor self.L = L self.H = H def clone(self): """ IMPORTANT NOTE: The clone method needs to call transferToCPP() on the cloned object to transfer the ownership of the clone to the cpp code """ cloned_ff = CustomFormFactor(self.L, self.H) cloned_ff.transferToCPP() return cloned_ff def formfactor_at_bottom(self, q): 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 bottomZ(self, rotation): return 0 def topZ(self, rotation): return self.H def get_sample(): """ Returns a sample with particles, having a custom form factor, on a substrate. """ # defining materials m_vacuum = ba.RefractiveMaterial("Vacuum", 0, 0) m_substrate = ba.RefractiveMaterial("Substrate", 6e-6, 2e-8) m_particle = ba.RefractiveMaterial("Particle", 6e-4, 2e-8) # collection of particles ff = CustomFormFactor(20*nm, 15*nm) particle = ba.Particle(m_particle, ff) particle_layout = ba.ParticleLayout() particle_layout.addParticle(particle) vacuum_layer = ba.Layer(m_vacuum) vacuum_layer.addLayout(particle_layout) substrate_layer = ba.Layer(m_substrate) # assemble sample sample = ba.MultiLayer() sample.addLayer(vacuum_layer) sample.addLayer(substrate_layer) return sample def get_simulation(sample): beam = ba.Beam(1, 1*angstrom, ba.Direction(0.2*deg, 0)) n = bp.simargs['n'] det = ba.SphericalDetector(n, -1*deg, 1*deg, n, 0, 2*deg) simulation = ba.ScatteringSimulation(beam, sample, det) simulation.options().setNumberOfThreads( 1) # deactivate multithreading (why?) return simulation if __name__ == '__main__': bp.parse_args(sim_n=100) sample = get_sample() simulation = get_simulation(sample) result = simulation.simulate() bp.plot_simulation_result(result) 
Examples/scatter2d/CustomFormFactor.py