A kinetic study of the rotation of polyatomic molecules
Planar B11- clusters have been introduced in recent years as molecular Wankel motors and tank tracks. They are molecular rotors with inner wheels that rotate almost freely in pseudo-rotating outer bearings. Molecular rotors have fascinating applications in the gas phase, in solution, in crystals, on surfaces, and in the biological environment. The associated rotational/pseudo-rotational energies appear with characteristic band structure, affecting the dynamics. Meanwhile, planar B11- clusters provide a model for studying the microscopic origin of the second law of thermodynamics for small systems. In this paper, we investigate the cyclic reaction path of B11- through 18 equivalent global minimum structures (GMi, i =1,2 ...18), these GMs are embedded in 18 cyclic potential wells and separated by 18 equivalent transition states with barrier Vb . If B11- is originally prepared in one of the 18 GMs, with energy below Vb, then it will then sequentially tunneling into the nearest global minimum structure, and so on, then to the next nearest GM, slowly all the GMs are occupied, at the same time, the entropy of occupying GM increases from a small value to a maximum value and gradually evenly distributed, but eventually does not return to the initial low value.
