Atomistic simulation of Mg₂SiO₄ and Mg₂ GeO₄ spinels: A new model

We have developed a new interatomic potential model for the simulation of ringwoodite, the high-pressure phase of Mg₂SiO₄, and its low-pressure analogue, Mg₂GeO₄ spinel. The main novelty is the addition of a breathing shell model that enables us to accurately describe the structural and elastic parameters of both spinels up to 15 GPa. Our model has also been applied to the two other Mg₂SiO₄ polymorphs in order to test its transferability. We find that although it is able to reproduce the structure and physical properties of wadsleyite, the breathing shell description is less successful with forsterite. The Mott-Littleton method has been used to calculate the energy of the intrinsic point defects in both spinels. The results indicate that these phases are likely to have the same defect population with the MgO partial Schottky defect predominating.