Scope and limitations

What PowderLine does not do. None of these is approximated silently: a recipe that asks for one is refused at validation, or the schema has no field for it.

Data

Not supported	What PowderLine accepts
Neutron data	X-ray data only.
Time-of-flight and energy-dispersive data	Constant-wavelength data.
Data on a Q or d-spacing axis	2θ in degrees. Convert Q or d to 2θ in the reader that builds xrd_data.
Kα doublets and laboratory X-ray data	GSAS-II recipes are single-wavelength (type: "PXC"). TOPAS recipes state one emission line. easydiffraction has a Kα2 line, which reaches the engine but has not been verified against laboratory data.
Several patterns in one refinement (multi-histogram)	One pattern per recipe.
Repairing data	PowderLine accepts or refuses data, and never changes it. Sorting, unit conversion, weights from counts and masking belong to your reader.

Models

Not supported	Notes
Pawley and Le Bail fitting	Every phase is a structure. For a fit without a structure, use single-peak fitting (gsasii.spf, topas.spf).
Magnetic structures	X-ray data only.
Anisotropic size and strain models (uniaxial, ellipsoidal, Stephens)	GSAS-II and TOPAS take isotropic size and strain. easydiffraction has no sample broadening: its profile is the instrument’s.
Preferred orientation other than March–Dollase	No spherical harmonics, no second axis.
Fundamental-parameters profiles (TOPAS fp)	Out of scope.
Extinction and surface roughness	In no engine schema.
Sample absorption and sample displacement in GSAS-II recipes	GSAS-II’s sample parameters are not exposed. TOPAS has a capillary absorption correction; easydiffraction has absorption and displacement slots.
Bragg–Brentano and other specimen corrections in TOPAS recipes (Specimen_Displacement, Absorption, goniometer radii beyond the axial models)	Not in the TOPAS schema.

Refinement features

Not supported	Notes
Bounds in GSAS-II recipes	GSAS-II applies limits only after a fit (Bounds).
User-defined constraints between atoms (shared occupancies, ADPs tied across sites)	Only the space-group symmetry ties parameters.
Restraints and rigid bodies	In no engine schema.
Refinement strategies inside one recipe (sequential or iterative steps)	One refinement per recipe. Chain runs yourself through the output recipe (Run a series).
A choice of minimizer	Each engine uses its own least squares. easydiffraction’s minimizer must be stated, and accepts only "lmfit (leastsq)".
Relaxed checks	There is no mode that switches validation rules off, for example the occupancy range.

Engines and versions

Not supported	Notes
Engines other than GSAS-II, TOPAS and easydiffraction	Each engine needs its own gateway (Adding an engine).
Translating a recipe between engines	A recipe is written in one engine’s terms. Only the core blocks move between engines.
Single-peak fitting with easydiffraction	gsasii.spf and topas.spf only.
TOPAS 7 and other TOPAS versions	topas.* recipes are verified against TOPAS 6 and declare it only.
Running TOPAS outside Windows	tc.exe runs on Windows. Elsewhere a TOPAS recipe validates and its input files are written, without a run.
Other GSAS-II or easydiffraction versions	Each environment pins the version the gateway requires (Versions).
Uaniso, scattering_types and preferred_orientation with easydiffraction’s CrysFML calculator	CrysPy only. CrysFML also reports no reflection list.

Tools around the recipe

Not supported	Notes
Reading CIF files	The structure arrives as a phase block that you or your tooling write.
Building recipes	PowderLine checks recipes strictly and leaves building them to the tool that knows where the data came from.
Reading raw data files	Your reader fills xrd_data with the arrays.
Fetching structures from a database (Materials Project or others)	Not part of PowderLine.

Why PowderLine reads no CIF and builds no recipe is explained on Recipes.