FIRST PRINCIPLES INVESTIGATION OF HOST EXCITATION OF LAPO4, LA2O3 ANDALPO4

The nature of optical excitations near the band gap of lanthanum oxide , aluminum phosphate and lanthanum phosphate is studied using first pr inciples cluster and band structure methods. It is shown that absorpti on near the band edge in phosphates involves excitations from the phos phate-like bonding states near the top of the valence band (VB) to the phosphate-like anti-bonding states near the bottom of the conduction band (CB).