Comparative study of the electronic structure of two laser crystals:: BeAl2O4 and LiYF4 -: art. no. 115101

The ground-state electronic structure and bonding of two important laser crystals, BeAl2O4, and LiYF4, were calculated using a first-principles method based the local approximation of the density-functional theory. The results were compared with similar calculations on several other laser crystals including yttrium aluminum garnet (Y3Al5O12). The;geometry of each crystal was optimized first with all internal parameters relaxed. The bulk moduli B were obtained by fitting the calculated total energies at different volumes to the Murnaghan equation of state. It was found that LiYF4 (B = 90.0 GPa) is much softer than BeAl2O4 (B =217.3 GPa). In BeAl2O4, Be and Al atoms have very similar local electronic structure and the crystal resembles that of alpha -Al2O3 (sapphire). LiYF4 is a highly ionic crystal while BeAl2O4 has a significant amount of covalent mixing. The density of states, their atomic and orbital decompositions, the effective charges, the bond order, and the charge distributions in these two crystals are presented and contrasted.