Fullerene C46: An unexpected non-classical cage

► The ground-state of fullerene C46 is a non-classical isomer (C2v:10-1) with a square. ► The low-lying non-classical isomers with square(s) exhibit large HOMO-LUMO gaps. ► The effects of incorporating a square are two-fold for species C2v:10-1. ► The relative thermodynamical stability survey based on Gibbs function is calculated.