Hexavacancies in crystalline silicon

The kinetics of disorientation of $B_{80}^4$centers is studied. The reorientation energy of the centers is determined to be $\sim1.5$  eV. Based on the fact that this value is close to the energy of hexavacancy transition from the ground state to the first metastable state, it is concluded that the $B_{80}^4$ center is a ring hexavacancy. The reorientation mechanism is explained by the hexavacancy transition to the metastable state and, then, to a state with a new orientation.