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Title: Structure and ionic diffusion of alkaline-earth ions in mixed cation glasses

A series of mixed cation silicate glasses of the composition A2O – 2MO – 4SiO2, with A=Li,Na,K and M=Ca,Sr,Ba has been investigated by means of molecular dynamics simulations in order to understand the effect of the nature of the cations on the mobility of the alkaline-earth ions within the glass network. The size of the alkaline-earth cation was found to affect the inter-atomic distances, the coordination number distributions and the bond angle distributions , whereas the medium-range order was almost unaffected by the type of the cation. All the alkaline-earth cations contribute to lower vibrational frequencies but it is observed that that there is a shift to smaller frequencies and the vibrational density of states distribution gets narrower as the size of the alkaline-earth increases. The results from our modeling for the ionic diffusion of the alkaline-earth cations are in a qualitative agreement with the experimental observations in that there is a distinct correlation between the activation energy for diffusion of alkaline earth-ions and the cation radii ratio. An asymmetrical linear behavior in the diffusion activation energy with increasing size difference is observed. The results can be described on the basis of a theoretical model that relates the diffusion activationmore » energy to the electrostatic interactions of the cations with the oxygens and the elastic deformation of the silicate network.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0022-3093
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Non-Crystalline Solids; Journal Volume: 422
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
Country of Publication:
United States
glass; molecular dynamics; alkaline-earth; structure; diffusion