The electronic structures, dielectric functions,
complex refractive indices and absorption spectra for a perfect
PbWO4 (PWO) crystal and the PWO crystals containing lead vacancy
VPb2− have been calculated using a full-potential
(linearized) augmented plane-wave (LAPW) + local orbitals (LO) method
with the lattice structure optimized. The peaks of the absorption
spectra corresponding to the electronic transitions have been studied.
The calculated results indicate that the absorption band of the perfect PWO
crystal does not occur in the visible region. However, the PWO crystal
containing VPb2− has two additional absorption bands in
this region. The two bands can be well decomposed into four
gaussian-shape bands peaking at 350 nm, 405 nm, 550 nm and 670 nm,
respectively, which coincide well with the 350 nm, 420 nm, 550 nm and
680 nm absorption bands measured in PWO crystals. Therefore, it can be
concluded that the 350 nm, 420 nm, 550 nm and 680 nm absorption bands are
related to the existence of VPb2− in the PWO crystal.