Molecular dynamics simulations of calcium aluminate glasses |
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Authors: | Eun-Tae Kang Alex C. Hannon |
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Affiliation: | a Department of Ceramic Engineering, Gyeongsang National University, Jinju 660-701, Republic of Korea b ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom |
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Abstract: | Molecular dynamics simulations of a series of calcium aluminate glasses have been carried out using empirical potentials with a covalent term. The simulations closely reproduce the total neutron correlation function of glasses with 30 and 38 mol% Al2O3 and physical properties such as elastic constants. For compositions close to the eutectic 37 mol% Al2O3, aluminum is tetrahedrally coordinated by oxygen, but the proportion of five-fold and six-fold coordination and also edge-sharing tetrahedra gradually increases with increasing Al2O3 content. The coordination number for oxygen around calcium atoms is close to 6 and this involves a larger coordination at a shorter, well-defined distance, followed by a smaller coordination with a broader range of distances. When the Al2O3 content decreases, the calcium aluminate structure becomes depolymerised and the average ring size increases. Also reported is an X-ray photoelectron spectroscopy measurement on a glass sample with 38 mol% Al2O3, which shows that 38.6 ± 0.9% of the oxygens are non-bridging, in excellent agreement with the simulations. |
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Keywords: | 61.43.Bn 61.43.Fs 79.60.Ht |
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