Changes of structure in potassium depleted binary silicate glass studied by MD

Ab-initio (DFT) molecular dynamics was used to simulate the structural relaxation of 15K2O·85SiO2 glass after the removal of potassium ions. The simulations mimic the experimental findings for potassium-silicate glass irradiated with medium-energy electrons (tens of keV) during which glass becomes fully depleted of alkali ions after some time of the continuous irradiation. Simulations include both volume compression and expansion, found experimentally at different doses. Non-bridging oxygen atoms were created by potassium removal from the prepared glass structure. Changes after alkali atoms removal and the following structural relaxation were characterized in terms of PP RDFs and PP CNFs. The preferential formation of O–O bonds after alkali atom removal was confirmed. The peroxide/ozonide bonds were pretty stable; they do not decay until 2000 K. The relaxation is driven in way Continuous Random Network modified by allowed O–O bonds is formed. Important role of structural defects, namely 5-coordinated Si and sharing edge polyhedra, was confirmed by the direct view of network evolution.