The Disappearing Quartz-Coesite Path: the Phase Transition Mechanism of Silicon Dioxide from Machine Learning Simulations

This study systematically investigates the structural phase transition mechanisms of silicon dioxide under high pressure using a high-dimensional neural network potential model combined with the stochastic surface walking algorithm. First, a global potential energy surface encompassing quartz, coesite, stishovite, and amorphous states was constructed, and the thermodynamic phase diagram was plotted, revealing the thermodynamic stability advantage of stishovite in high-pressure regions. Further analysis demonstrated that the energy barrier for the quartz-to-stishovite transition path significantly decreases under high pressure, indicating strong kinetic feasibility, whereas the coesite-to-stishovite pathway follows a single transition state mechanism with a slightly increasing energy barrier under pressure. Regarding the amorphization transition, the key role of the symmetry-deficient low-energy structure group in the high-pressure amorphization of quartz was clarified through sampling and identification, unveiling the "short-range order—medium-range disorder" structure as a defining characteristic of the amorphous state. Notably, no effective quartz-coesite transition path was observed during the study, suggesting that the amorphization transition inhibits this transformation pathway and revealing the kinetic principles underlying the absence of the quartz-coesite transition. This work comprehensively explores the mechanisms of crystalline and amorphous phase transitions in silicon dioxide under high pressure and provides theoretical foundations and methodological paradigms for high-pressure simulation studies of complex oxides.