Direct constituents (one level).
Element symbol → cumulative weight fraction across the recursive
expansion. Only present for materials that bottom out in elements
with a chemistry.symbol. Mixtures whose components lack chemistry
data contribute their direct entries to direct but not to
flat.
The material whose composition is being expanded.
Recursive composition expansion.
directis the material's own composition entries (one level).flatis the recursive walk down to leaf elements / unmodeled bottoms, expressed as element-symbol → cumulative weight fraction.A mixture of mixtures resolves to atomic-symbol fractions — useful for "does this contain iron?" queries that don't care about the intermediate alloy.