Band structure features of nonlinear optical yttrium aluminium borate crystal

The band structure and density of states are calculated for yttrium aluminium borate YAl3(BO3)(4) (YAB) single crystal, which is a nonlinear optical crystal, using the full-potential linear augmented plane wave method. Our calculations show that this crystal possesses a direct energy gap (Gamma) of 5.1 eV in reasonable agreement with experimental value of 5.70 eV. The small discrepancy between the experimental and the calculated values of the energy gap is typical for the local density approximation. Our calculations show coexistence of strong and weak hybridizations between the states. The calculated density of states was compared reasonably well with our experimental density of states measured by Xray photoelectron spectroscopy with respect to peak positions but not with respect to peak heights. This could be attributed to the presence of defect states. (C) 2008 Elsevier Masson SAS. All rights reserved.