Also known as CH5+, CH5(+), protonated methane, carbonium
In chemistry, methanium is a complex positive ion with formula (metastable transitional form, a carbon atom covalently bonded to five hydrogen atoms) or (fluxional form, namely a molecule with one carbon atom covalently bonded to three hydrogen atoms and one dihydrogen molecule), bearing a +1 electric charge. It is a superacid and one of the onium ions, indeed the simplest carbonium ion.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).