# Dynamics of Beryllocene

The molecular structure and dynamics of beryllocene are investigated using the Car--Parrinello projector augmented wave method. In the ground state, the molecule prefers a \monopenta-coordinat-ed conformation of $C_{\rm S}$ symmetry. At finite temperature, beryllocene undergoes rapid hapticity changes with a frequency of 1--5 $\times$ 10$^{12}$ \ps. This occurs by means of two mechanisms, each corresponding to a saddle point of the potential surface elevated 5 and 8 \kjpermol \ above the minimum, respectively. The saddle points have $C_{\rm S}$ and $C_{2h}$ symmetry, respectively. The geometric and electronic structure at finite temperature are discussed.