Abstract
Aluminate glasses are difficult to prepare as they do not contain traditional networkformers, but they are promising materials for optical applications. The atomicstructure of calcium aluminate glasses has been studied using several experimentaltechniques. The current study uses molecular dynamics to obtain a model of a(CaO)0.625(Al2O3)0.375 glass close to the eutectic. The glass consists of a tetrahedral alumina network with averagenetwork polymerization of n = 3.3. Ca actsas a network modifier with average coordination of 6.2. Ca is typically coordinated to three bridging oxygens(Ob) and three non-bridgingoxygens (Onb), withCa–Onb bonds noticeablyshorter than the Ca–Ob bonds. A new method of analysing modifier cation coordination ispresented, which specifically shows the distribution of Ca coordinationNCaO in terms ofcombinations of NCaOb and NCaOnb. Ob is most often coordinated to two Al plus two Ca, andOnb is most often coordinated to one Al plus three Ca. The typical coordinations of Ca,Ob,and Onb all have a noticeable similarity to those for the5CaO·3Al2O3 crystal. The Ca–Ca distribution shows a clear similarity to that for(CaO)0.5(SiO2)0.5 glass, and this is attributed to the equal atomic number densities of Ca in these glasses.
Published Version
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