DECAY OF THE SELF-TRAPPED EXCITON AND FRENKEL-PAIR FORMATION IN NAF -AN AB-INITIO STUDY

The adiabatic potential-energy surface connecting the triplet self-tra pped exciton state to up to the third-nearest-neighbor Frenkel pairs i s calculated for Na18F4 clusters using an all electron ab initio Hartr ee-Fock approach. The correlation effect brings out more details, such as the positions of the nearest-neighbor Frenkel pairs, but does not alter substantially the result of unrestricted Hartree-Fock calculatio n. No potential barrier larger than 0.2 eV is observed up to the third -nearest-neighbor separation, and it is concluded that the self-trappe d excitons can evolve dynamically into stable Frenkel pairs.