Density functional theory calculations of structural, electronic and optical properties of LaPO4:Eu

• Structural, electronic and optical properties of LaPO4:Eu are investigated.
• Eu doping introduces impurity energy levels to make band gap decreased.
• O(2p)–Eu(4f) charge transfer energy is calculated.
• We assign the optical transitions according to calculated results.
• The occupation of Eu3+ in LaPO4 synthesized in this work is determined.

Monoclinic LaPO4 and LaPO4:Eu have been prepared by the hydrothermal method. The phase composition, UV–Vis absorption spectrum, excitation and emission spectra of as-obtained products were measured. Theoretical calculations of the structural, electronic and optical properties of LaPO4 and LaPO4:Eu were also carried out. The results indicated that the lattice parameters, energy gap and optical properties were in good agreement with the experimental results. The impurity energy levels induced by the 4f states of Eu expanded the absorption edge and decreased the band gap. The charge transfer energy of O(2p)–Eu(4f) calculated was about 4.41 eV, which was close to the value achieved in excitation spectrum (4.5 eV).