Jahn-Teller instability in cationic boron and carbon buckyballs B80+ and C60+: a comparative study

This paper investigates the Jahn-Teller effect in the icosahedral cation B-80(+) and compares the descent in symmetry with that in C-60(+). For both cations the icosahedral ground state is a H-2(u) state, which exhibits a H circle times (g circle plus 2h) Jahn-Teller instability. A detailed construction of the potential energy surface of B-80(+) using different DFT methods including B3LYP/6-31G(d), VWN/6-31G(d), PBE/TZP and PBE/6-31G(d) shows that, contrary to C-60(+), which prefers D-5d symmetry, the ground state of B-80(+) adopts S-6 point group symmetry. A D-3d structure is identified as a saddle point among the S-6 minima of B-80(+). The distortion of D-3d to S-6 in B-80(+) is attributed to a superposition of Jahn-Teller and pseudo-Jahn-Teller effects. Imaginary modes, transforming as the g(g) representation, which are present in neutral icosahedral B-80, form the dominant symmetry breaking active modes. The pronounced difference between the JT effects in the boron and carbon buckyball cations is due to the plasticity of the boron caps. The calculated Jahn-Teller stabilization of B-80(+) is nearly 1549 cm(-1) (PBE/TZP), which exceeds the stabilization of 596 cm(-1) computed for C-60(+) at the same level.