INFLUENCE OF STRUCTURE ON THE OPTICAL-SPECTRA OF EU3+ IN PB(PO3)2 GLASS - MOLECULAR-DYNAMICS SIMULATION AND CRYSTAL-FIELD THEORY

An investigation of the structural factors which lead to the marked differences between various spectral features of rare-earth-metal ions doped in metal metaphosphate and silicate glasses is reported. The investigation was based on a simulated structural/spectral model of an Eu3+-doped lead metaphosphate glass [Eu3+ : Pb(PO3)2] that was compared to a previously reported Eu3+-doped sodium disilicate glass [Eu3+ : Na2Si2O5]. The models were generated with a computational method that couples molecular dynamics simulation and point-charge crystal-field calculations. It is proposed that the marked differences in several spectroscopic features of Eu3+ ions doped in a lead metaphosphate glass are essentially due to a reduction in the width of the energetic distribution of local fields experienced by the Eu3+ ions. This distribution is shown to be influenced considerably by the presence of medium-range order in the local environment of the Eu3+ ions due to the lack of rigidity of the phosphate backbone.