Demo datasets

The repository ships four simulated neutron reflectometry datasets for trying out the constraint features described in material and model setup. They live in examples/datasets, together with a full write-up of each demo and the script that regenerates them.

All four are ORSO .ort files simulated from a known structure with 4 % noise and 5 % dQ/Q resolution, so every demo has a right answer to compare the fit against. The ground truth is recorded in each file’s header, and each header also carries the sample structure in the ORSO model language, so the files can be opened in two ways:

• Model › Load a sample › Load sample from file builds the layer stack for you, with the true thicknesses, roughnesses and SLDs as starting values. Change those starting values before fitting, so there is something to find.

• Experiment › Load experiment(s) from file(s) loads the reflectivity curve, which also works with a hand-built sample.

Dataset	Demonstrates
two_layer_film.ort	A two-layer film whose total thickness is known (exactly 90 Å) - the thickness budget and the derived total film thickness.
swapped_layers.ort	A layer-ordering inequality: started from the swapped guess, the fit only recovers the truth with a ≤ constraint between the two thicknesses.
ni_ti_multilayer.ort	A [Ti / Ni] × 8 repeating multilayer with a Bragg peak that pins the period - the Constant period Λ and Conformal roughness recipes.
dppc_monolayer.ort	A DPPC monolayer at the air/D2O interface - the surfactant recipes (equal head/tail area per molecule, solvent roughness).

Note

For ni_ti_multilayer.ort the loaded stack arrives flattened (8 × [Ti | Ni] becomes 16 layers in one assembly); rebuild it as a Repeating Multi-layer by hand for the constant-period demo. For dppc_monolayer.ort the loaded stack is the slab equivalent of the surfactant; replace it with a Surfactant layer assembly for the surfactant recipes.