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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)
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)
Ab initio molecular dynamic (AIMD) simulations were performed to calculate the equation of state (EOS) of CaSiO 3 per-ovskite at mantle pressure–temperature conditions. At temperatures above 2000 K, even though the hydrostatic crystal structure is metrically tetragonal in the pressure range of 13–123 GPa, the symmetry of the elastic moduli is consistent(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)
The testbed project has the ambition to push the practical possibilities of atomistic simulations forward to the point where we can perform realistic calculations on important environmental processes. The project has three components: the science driving the project, the development of the simulation codes, and setting up a grid infrastructure for this(More)
In order for existing grid middleware to remain viable it is important to investigate their potential for integration with emerging grid standards and architectural schemes. The Open Grid Services Architecture (OGSA), developed by the Globus Alliance and based on standard XML-based web services technology, was the first attempt to identify the architectural(More)