From the outset, the project focused on the role of microscopic defects in controlling the mechanical behavior of rocks. Particular attention was given to grain boundaries—the interfaces between individual crystals—which play a crucial role in controlling large-scale flow. In particular, we resolved a long-standing discrepancy between theoretical and experimental descriptions of grain boundaries in magnesium oxide (MgO, a component of the lower mantle)). By incorporating realistic features such as non-stoichiometry and point defects, we reconciled simulations with laboratory observations.
Building on this, we extended our modeling work to olivine, a major mantle mineral. We were the first to describe tilt and twist boundaries in olivine and revealed the intricate structural complexity of real grain boundaries in silicate materials. These advances provide essential inputs for more accurate modeling of rock flow in the Earth’s mantle.
In parallel, we used high-resolution nanomechanical testing within TEM setups to access deformation mechanisms at unprecedented small scales. One of the project’s most significant achievements was the first direct observation and measurement of a grain boundary flowing after undergoing amorphization—a transition from a crystalline to a glassy state that enables boundary sliding. This mechanism had previously been proposed theoretically but never demonstrated with such clarity.
We also characterized how amorphous olivine deforms across a strain-rate range spanning more than 20 orders of magnitude. This invariance is unprecedented in materials science and strongly contrasts with the behavior of other key minerals, such as bridgmanite, which exhibits different deformation mechanisms under natural versus laboratory conditions. These findings demonstrate the importance of new deformation pathways and highlight the inadequacy of relying solely on traditional scaling laws.
Another key outcome was the identification of dislocation climb as a dominant deformation mechanism at geological strain rates—both in the deep mantle and, remarkably, in quartz in the lithosphere. This mechanism has long been overlooked due to its slow nature and the experimental challenges in accessing it, yet our findings place it at the center of rock deformation processes at natural conditions.
These scientific results have been disseminated through numerous peer-reviewed journal publications, presentations at major international conferences, and invited talks. They have stimulated cross-disciplinary interest, particularly among researchers in mineral physics, geodynamics, materials science, and solid-state physics.
