Triplet-state electronic excitations in quartz were studied using density f
unctional theory (DFT). By using periodic boundary conditions, the lattice
response and electronic structure relaxations can be determined in the bulk
. Several self-trapped exciton (STE) states have been discovered, in additi
on to the oxygen-distorted state, which was originally predicted 10 years a
go. One of these stales is a silicon-distorted state that lies energeticall
y close to the oxygen-distorted state. The results reveal that these two ma
jor STE states are likely responsible for two distinct luminescence bands.
The luminescence energies for STE states of impurities and intrinsic defect
s were also determined. (C) 2000 Elsevier Science B.V. All rights reserved.