Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?

Superconducting behavior even under harsh ambient conditions is expected to occur in La@C₆₀ if it could be isolated from the primary metallofullerene soot when functionalized by CF₃ radicals. We use ab initio density functional theory calculations to compare the stability and electronic structure of C₆₀ and the La@C₆₀ endohedral metallofullerene to their counterparts functionalized by CF₃. We found that CF₃ radicals favor binding to C₆₀ and La@C₆₀ and have identified the most stable isomers. Structures with an even number m of radicals are energetically preferred for C₆₀ and structures with odd m for La@C₆₀ due to the extra charge on the fullerene. This is consistent with a wide HOMO-LUMO gap in La@C₆₀(CF₃)_m with odd m, causing extra stabilization in the closed-shell electronic configuration. CF₃ radicals are both stabilizing agents and molecular separators in a metallic crystal, which could increase the critical temperature for superconductivity.