J. P. Brodholt

Learn More
The temperature anomalies in the Earth's mantle associated with thermal convection can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obtain directly through laboratory experiments. We have therefore(More)
[1] We investigate the effect of pressure on the electronic spin state of ferric iron on Al-bearing MgSiO 3-perovskite using first-principle computations. Ferric iron (6.25 mol%) and Al (6.25 mol%) substitute for Mg and Si respectively. Five substitution models on different atomic position pairs are examined. Our results show that spin state transition from(More)
We consider three independent methodologies for calculating thermal equation of state (EOS) of the major earth-forming mineral, orthorhombic MgSiO 3 perovskite: molecular dynamics (MD), lattice dynamics (LD) and Debye model (DM). Using the most recent developments in the GULP code, we derive a new interatomic potential, which is demonstrated to be extremely(More)
We have used high-temperature ab initio molecular dynamic simulations to study the equation of state of orthorhombic MgSiO 3 perovskite under lower mantle pressure^temperature conditions. We have determined the Gru « neisen parameter, Q, as a function of volume. Our state-of-the-art simulations, accurate to within 10%, resolve the long-standing controversy(More)
We report the dynamics of the structure of CaSiO 3 perovskite from ab initio molecular dynamics (AIMD) calculations at high pressure (P up to 130 GPa) and high temperature (T up to 5000 K). Our calculations indicate three separate stability fields: orthorhom-bic, tetragonal and cubic, with the tetragonal phase dominating the pressure and temperature region(More)
[1] Finite temperature ab initio molecular dynamics calculations were performed to determine the high temperature elastic and seismic properties of the perovskite and post-perovskite phases of pure end-member Al 2 O 3. The post-perovskite phase exhibits very large degrees of shear-wave splitting. The incorporation of a few mole percent of Al 2 O 3 into(More)
Ultralow-velocity zones (ULVZs) are regions of the Earth's core-mantle boundary about 1-10 kilometres thick exhibiting seismic velocities that are lower than radial-Earth reference models by about 10-20 per cent for compressional waves and 10-30 per cent for shear waves. It is also thought that such regions have an increased density of about 0-20 per cent(More)
Post-perovskite MgSiO(3) is believed to be present in the D'' region of the Earth's lowermost mantle. Its existence has been used to explain a number of seismic observations, such as the D'' reflector and the high degree of seismic anisotropy within the D'' layer. Ionic diffusion in post-perovskite controls its viscosity, which in turn controls the thermal(More)
In this article we describe the eMinerals mini grid, which is now running in production mode. This is an integration of both compute and data components, the former build upon Condor, PBS and the functionality of Globus v2, and the latter being based on the combined use of the Storage Resource Broker and the CCLRC data portal. We describe how we have(More)