PNNL

Abstract

The structure and properties of self-trapped excitons (STE), were investigated using density functional theory (DFT) and wavefunction based methods (UHF, UMP2, CAS-SCF and ccsd(t)). The accuracy of DFT results was investigated by performing more accurate electronic structure calculations on cluster configurations extracted from bulk DFT calculations of the STE in alpha-quartz. Two luminescent STEs were found, as well as a non-radiative state at a crossing of the singlet and triplet surfaces. It was determined that the PW91 functional under-estimates the energy of the triplet state, and that this error is greater with greater delocalization of the excess spin density of the state.