Metastability of the three-dimensional prismane C-8 carbon cluster

Stability of recently predicted cage-like carbon cluster Cs (prismane) agai nst its transformations to lower energy structures is studied theoretically . The smallest energy barrier inhibiting prismane transformation is shown t o be 0.44 eV, in qualitative agreement with the value of activation energy for prismane decay calculated by molecular dynamics simulations. A rather h igh value of the barrier suggests the possibility of experimental observati on of this cluster at ambient pressure.