A comparison of structural models of Tb3Al5O12 and Nd3Al5O12 glasses obtained when using x-ray data alone and when x-ray and neutron data are combined

X-ray diffraction experiments, including Anomalous X-ray Diffraction, have been carried out on Tb3Al5O12 and Nd3Al5O12 glasses. In addition, neutron diffraction and isotopic substitution experiments have been carried out for Nd3Al5O12. The data has been analysed by direct Fourier transform methods and by refinement of atomistic structures obtained from Molecular Dynamics simulations. For Nd3Al5O12 good agreement between the Molecular Dynamics simulations and all the experimental data was obtained. The Molecular Dynamics configuration was refined further using Reverse Monte Carlo methods to obtain a final atomistic configuration. The Nd3Al5O12 Molecular Dynamics configuration was refined using the X-ray data alone and the results show that the final configuration was in worse agreement with the data than the original Molecular Dynamics calculation. From this result it was concluded that in order to obtain a good atomistic model of Tb3Al5O12 it is essential to include at least one neutron diffraction measurement in the Molecular Dynamics - Reverse Monte Carlo refinement.