Molecular dynamics study the effect of the ratio Ca/Al on CaO-Al2O3-SiO2 structure

Abstract

The microstructure of CaO-Al2O3-SiO2(CAS)glass system is studied by molecular dynamics method.When Ca/Al equals to 1/2,which is called tectosilicate glass system,CAS is not a totally full network as conventional theories,but with some Non-Bridging Oxygen(NBO).The theoretical result proves Stebins's experimental conclusion.The result also reveals that when the ratio of Ca/Al is greater than 1/2 Al is preferred inserting in polymerized network to the end of polymerized network,when the ratio of Ca/Al is less than 1/2,the situationis is contrary.The “aluminium avoidance” principle believes that Al—O—Al linkages are energetically less favorable than Al—O—Si linkages in CAS glass system.However when the ratio of Ca/Al alters down across 1/2,there are some Al—O—Si linkages change to Al—O—Al and Si—O—Si linkages.