Fig. 3. Hindering of methyl rotor dynamics by nuclear delocalization in toluene molecule.

A Global minima and transition state of Me rotor. Histogram of the Me rotor’s dihedral angle (B) and out-of-plane dihedral angle (C) computed from classical MD (blue) and PIMD (red). D Time evolution of the Me rotor for classical MD (top) and PIMD (bottom) simulations. The red rectangles indicate some of the localized states in the dynamics. The size of the bins are 5 ps × 6^∘. The simulations were done at room temperature at the sGDML@CCSD(T) level of theory. E Methyl rotor’s PES and its transition state (TS) energy for different fixed values of the C₂ − C₃ distance (marked in red). In a localized state, there is a quasi-linear correlation between C₂ − C₃ and C₂ − C₇ distances, $d_{C_2-C_7}~-d_{C_2-C_3}$ (See Supplementary Note 7 for further details).