Structural Heterogeneity of MgSiO3 Liquid and Its Connection with Dynamical Properties

Silicate melts not only govern key processes in the Earth's early evolution, but also significantly influence its interior dynamics today. MgSiO3, a primary component of silicate melts, undergoes significant structural changes and exhibits complex macroscopic properties from the Earth's surface to the core-mantle boundary. Despite extensive studies, the atomic structure, densification mechanisms, and their connection to dynamics remain unclear. In this Letter, using molecular dynamics simulations with a deep neural network potential, we investigate the atomic structure of MgSiO3 liquid. Our results reveal significant structural heterogeneity in MgSiO3 liquid, with distinct Mg- and Si-enriched regions present throughout the entire mantle pressure range. This heterogeneity offers a new perspective on understanding the densification mechanism, and explains the atomic origin of the viscosity anomaly, as the lifetime of structural heterogeneity aligns well with the Maxwell relaxation time. Our findings provide new insights into the behavior of silicate melts under extreme conditions.