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

An investigation of the structural factors which lead to the marked di fferences between various spectral features of rare-earth-metal ions d oped in metal metaphosphate and silicate glasses is reported. The inve stigation was based on a simulated structural/spectral model of an Eu3 +-doped lead metaphosphate glass [Eu3+ : Pb(PO3)2] that was compared t o a previously reported Eu3+-doped sodium disilicate glass [Eu3+ : Na2 Si2O5]. The models were generated with a computational method that cou ples molecular dynamics simulation and point-charge crystal-field calc ulations. It is proposed that the marked differences in several spectr oscopic features of Eu3+ ions doped in a lead metaphosphate glass are essentially due to a reduction in the width of the energetic distribut ion of local fields experienced by the Eu3+ ions. This distribution is shown to be influenced considerably by the presence of medium-range o rder in the local environment of the Eu3+ ions due to the lack of rigi dity of the phosphate backbone.