MOLECULAR-DYNAMICS SIMULATION OF THE TRIVALENT EUROPIUM ION DOPED IN SILICA AND SODIUM DISILICATE GLASSES

Using the molecular dynamics technique, the Eu3+-doped SiO2 and Na2O.2SiO2 glasses have been simulated. In order to examine the local structure about the Eu3+ ions, results are presented in the form of radial and cumulative distribution functions and bond angle distributions. The average coordination number of the Eu3+ ion was found to be four and six in SiO2 and Na2O.2SiO2 glasses, respectively. The distortion of each Eu3+ local environment is quantified by calculating its quadrupole moment ellipsoid. It is shown that the local structure of the europium ions is influenced to a greater degree by its bonding and energetic requirements than by the topology of the silicate framework. The simulations suggest that the europium ions form quasi-molecular complexes. The role of the europium ion in the formation of 'free' oxygens has also been described and a mechanism proposed.