TiC: A stable T -symmetry hollow cage.

A stable T -symmetry TiC cage was systemically investigated using density functional theory. The structure of TiC is a hollow cage with twelve TiC subunit of three pentagons and one hexagon. The calculated frequencies are in the range 95.1 cm-1423.9 cm. There are no imaginary frequencies, showing its kinetic stability. Ab initio molecular dynamics simulations demonstrate that the topological structure of cage-like TiC cluster was well maintained when the effective temperature is up to 1139 K. The natural bond orbitals analysis shows that the d orbit of Ti atoms form four σ bonds with the neighboring four carbon atoms in each TiC subunit playing an important role in the cluster stability. The molecular frontier orbitals analysis indicates that TiC cage has a narrow HOMO-LUMO gap with metal-like property. It would be expected to enrich the species of hollow metal carbide clusters.