Reverse MC for SASview

[dehoni]

At the magnetic SANS meeting 20/04/2023 it was suggested to add reverse MC simulations to SASview introduced in recent publications (Science case: https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.202008683, RMC SAS code: https://onlinelibrary.wiley.com/doi/pdf/10.1107/S1600576722009219).
The approach has the advantage to describe anisotropic structure factor from self-assembly processes. The model simulates a two-dimensional detector image, accounting for magnetic scattering, instrument resolution, particle polydispersity without the need for explicit assumptions on physical force to describe the underlying particle interactions.
The output of the algorithm is a representation of the particle distribution and orientational distribution of magnetic moments.
The details of the particle shape and size are prefixed by using a form factor, so the existing form factors in SASview could be used.

The question is recurring to include external libraries and in particular simulation methods to describe and potentially fit data. It requires a group discussion how to do to use external modules as FittingOptions to create theory curves and the details of a suitable general workflow which would allow people to link SASview with their simulation code.

Alternatively, there is also the idea to “Extend generic scattering calculator with tabs for other simulators” (https://github.com/orgs/SasView/discussions/2189). In this case, the RMC code would provide the real space model. The generic scattering calculator would take care of the instrument/magnetic geometries. To the created theory curve one would need to apply instrument resolution, size distribution, particle form factor. Still, the fitting engine would trigger iteration of a simulation until convergence.