MD simulation of microstructure evolution and stress‐field modulated crack propagation in LAS glass via ion exchange

Abstract As a widely used screen protection material, chemically strengthened alkali‐aluminosilicate glass exhibits non‐uniform and anisotropic mechanical behavior due to complex prestress distribution. In this study, based on the large‐scale atomic/molecular massively parallel simulator, both a nanoscale uniform ion exchange model and a sub‐microscale gradient exchange model were developed to investigate the effects of Li + –Na + and Na + –K + ion exchange on the microstructure and crack behavior of lithium aluminosilicate glass. Results show that the glass network remains stable after ion exchange, while modifier bonds are fine tuned. Li + makes the bond length of Li–O gradually recover after the initial shortening due to high polarization, while Na–O and K–O bonds stretch with strain. The preferential fracture of Si–O–Al bond leads to the change of Al 3+ coordination. Mechanical properties show a non‐monotonic trend with increasing exchange rate, driven by competing effects of the high polarization ability of Li + and the stuffing effect of larger ions such as Na + and K + . At the sub‐microscale, deeper ion exchange increases surface compressive stress and inhibits crack propagation, but also induces tensile stress concentration inside, which can promote crack propagation when excessive. This work provides insights into multi‐scale mechanical behavior of chemically strengthened glass and supports process optimization.