### 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 $1$ $\unicode{x212B}$.
• The incident angles are $\alpha_i = 0.2 ^{\circ}$ and $\phi_i = 0^{\circ}$.
  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 95 96 97 98 99  """ Custom form factor in DWBA. """ import bornagain as ba from bornagain import deg, angstrom, nm import cmath def sinc(x): if abs(x) == 0: return 1. else: return cmath.sin(x)/x class CustomFormFactor(ba.IFormFactorBorn): """ 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.IFormFactorBorn.__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 evaluate_for_q(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 get_sample(): """ Returns a sample with particles, having a custom form factor, on a substrate. """ # defining materials m_ambience = ba.HomogeneousMaterial("Air", 0.0, 0.0) m_substrate = ba.HomogeneousMaterial("Substrate", 6e-6, 2e-8) m_particle = ba.HomogeneousMaterial("Particle", 6e-4, 2e-8) # collection of particles ff = CustomFormFactor(20.0*nm, 15.0*nm) particle = ba.Particle(m_particle, ff) particle_layout = ba.ParticleLayout() particle_layout.addParticle(particle, 1.0) air_layer = ba.Layer(m_ambience) air_layer.addLayout(particle_layout) substrate_layer = ba.Layer(m_substrate) # assemble multilayer multi_layer = ba.MultiLayer() multi_layer.addLayer(air_layer) multi_layer.addLayer(substrate_layer) return multi_layer def get_simulation(): """ Returns a GISAXS simulation with beam and detector defined. IMPORTANT NOTE: Multithreading should be deactivated by invoking setNumberOfThreads(-1) """ simulation = ba.GISASSimulation() simulation.getOptions().setNumberOfThreads(-1) simulation.setDetectorParameters(100, -1.0*deg, 1.0*deg, 100, 0.0*deg, 2.0*deg) simulation.setBeamParameters(1.0*angstrom, 0.2*deg, 0.0*deg) return simulation def run_simulation(): """ Runs simulation and returns intensity map. """ simulation = get_simulation() simulation.setSample(get_sample()) simulation.runSimulation() return simulation.result() if __name__ == '__main__': result = run_simulation() ba.plot_simulation_result(result) 
CustomFormFactor.py