Dynamical structure factor calculations
This is still an experimental playground, please do not use for production.
Install with testing dependency group, e.g. from this directory
pip install . --group test
and run with pytest
pytest
You may need to update Pip to access the --group feature.
New code should be accompanied with appropriate tests; use
pytest --cov --cov-report term-missing
to get a breakdown of which lines are not covered by tests. (This can
also be found in the Github Actions output when making a Pull Request.)
As well as unit testing, code contributions must pass linting with
ruff check and ruff format.
The pytest-regressions package is used to create/test reference outputs for functions given particular input. This gives confidence that results do not change unexpectedly between versions, but such "regression tests" are not necessarily validated against an ideal or external reference.
So far we have implemented the simplest possible calculation from Mantid-Abins: a 1D fundamental spectrum in the fully-isotropic approximation. This is benchmarked against the equivalent calculation in Mantid by a Snakemake workflow in dev/validation:
To reproduce the result so closely it was necessary to apply similar
implementation details: the q_scaling_isotropic_incoherent_spectra
function computes mode intensities at Q = 1Å and bins them to a dense
spectrum before applying Q^n2/n! scaling and Debye—Waller factor for
the bin-centre Q values. In practice this gives an acceptable
discretisation error of ~0.1%.
Another minor discrepancy comes from the neutron scattering cross-section references.