BornAgain ≻ 25.0 ≻ Documentation ≻ Reference ≻ Sample model ≻ Particles ≻ Composite particles ≻ Mixture

Particle mixture

A Mixture is a probabilistic particle: at each placement, it resolves to one of its configured particle types — the possible outcomes — with probabilities given by the (internally normalized) abundance weights. This is especially suited to uncorrelated compositional disorder: random substitutions at lattice sites, or species mixing in dilute distributions.

mix = ba.Mixture()
mix.addParticle(particle_1, 0.8)
mix.addParticle(particle_2, 0.2)

mix.nbrParticles() returns the number of added particle alternatives (2 here), regardless of their abundance weights.

Equal abundances may also be expressed without normalization:

mix.addParticle(particle_1, 1)
mix.addParticle(particle_2, 1)

A Mixture can be used as the particle in Dilute2D or as the basis particle of an ordered structure such as RadialParacrystal.

Physics

Compared with Compound, which coherently sums the form factors of its constituents at fixed positions, Mixture represents the incoherent case: each particle type contributes to the scattered intensity independently, weighted by its abundance, with no interference between different types.

Examples