decomposition vs decompositional

decomposition is a noun but decompositional is not a noun.

Word	Noun	Adjective	Verb	Adverb
decomposition	Yes	No	No	No
decompositional	No	Yes	No	No

decomposition (noun)	decompositional (noun)
the analysis of a vector field
the organic phenomenon of rotting
(biology) the process of decay caused by bacterial or fungal action
(chemistry) separation of a substance into two or more substances that may differ from each other and from the original substance
in a decomposed state

decomposition (adjective)	decompositional (adjective)
	causing organic decay