Research

One of the most important unresolved problems in Earth Sciences remains the detailed understanding of the connection between the dynamical processes in the earth's interior and observations on the earth's surface. This endeavor requires a multidisciplinary approach of many different branches of earth's sciences such as mineral physics, seismology, geodynamics, geochemistry and petrology. Mineral physics is an essential and integral part of this challenge, it provides the link between direct observations and our understanding of the transport of mass, momentum and energy in the earth's interior. One major contraint for this challenge is provided by seismology. Seismological observations contain in principle rich information on the thermal and rheological properties of the earth's interior and its composition and dynamics. However, our ability to extract these properties from the seismological observations is largely limited by our ignorance of the elastic properties of minerals and mineral assemblages at relevant pressure and temperature conditions.

My research focuses on the determination of elastic constants of mantle minerals and mineral assemblages at relevant pressure and temperature conditions. To date I have conducted my research using state of the art computational techniques. These methods do not rely on the nature of bonding in materials or any experimental input. Since these methods are independent of the nature of bonding, they allow us to treat metals, insulators and semi-conductors on the same fundamental footing. This notion provides the basis for the applicability of these methods to any material (with the exception of superconductors). In all cases the computed results compare favorably with experimental observations. In the future I would like to expand my research directions and to conduct experiments or collaborate with experimentalists to combine theoretical and experimental techniques to gain new insights into the nature of bonding, phase relations, element partitioning, defect formation and rheological properties of major mantel minerals and assemblages.

My current research projects focus on different regions in the earth's interior:

• Lower mantle: The phase diagram of MgSiO3-perovskite at lower relevant lower mantle conditions. Elasticity of Mg-perovskite at high pressures.
• Transition zone: Prediction of elastic constants of wave velocities at high pressures. The wave velocities have recently been measured up to 10 GPa and are in very good agreement with the predicted wave velocities. Materials: Wadsleyite and Ringwoodite.
• Subduction zones: Can water be transported along subduction zones below the zone for arc magma generation? This issue has been a challenge for our understanding of dynamics in the earth's interior for over a decade. Experiments find that minerals with structurally bound water can be stable up to at least transition zone pressures. The presence of these minerals can have a profound effect on the physical characteristics of the earth's mantle. It is therefore important to understand the nature of hydrogen bonding to derive the distribution of water in the earth's mantle. Materials: Brucite, Portlandite and Superhydrous B.
• Oxides, especially magnesiowuestite, are thought to be abundant in the earth's lower mantle, and I started to investigate and MgO and FeO to assess the importance of magnetism in this oxides and their effect on elastic properties.

Techniques:

• Systematics
• Pairpotentials
• First principle calculations (VASP)
• Linear Augemented Plane-Waves (LAPW)
• Linear Response Calculations (ABINIT)