falass is an open-source C++ program developed by Andrew. It will generate a reflectivity profile from a molecular simulation pdb file. The software was designed explictly to allow for the use of coarse-grained simulations, allowing portability across both X-ray and neutron reflectivity (as it is only the scattering lengths that change).

falass will read in the molecular simulation trajectory file, and ‘cut’ the system into layers of user-defined thickness. The SLD profile of the system in the z-direction is then determined at a user-defined time resolution, the Abeles optical martix method is then used to find the reflectivity profile from the time-averaged SLD profile. If an experimental data file is given falass can then use a genetic fitting algorithm to match up the background of the experimental profile and scale the reflectivity profiles such that they have a minimum χ squared value.

We are actively recuiting alpha testers of the software, so if you are interested in making use of it please get in touch with Andrew and he will be happy to help out. Might even be able to advise and find computer time to run the simulations, if you ask nicely.

The software is freely available here, and it comes with some documentation detailing the use of the program and how to install it (currently runs from the command line). For full details of what falass does please speak to Andrew.