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The Earth's lower mantle is believed to be composed mainly of (Mg,Fe)SiO3 perovskite, with lesser amounts of (Mg,Fe)O and CaSiO3 (ref. 1). But it has not been possible to explain many unusual properties of the lowermost approximately 150 km of the mantle (the D" layer) with this mineralogy. Here, using ab initio simulations and high-pressure experiments, we(More)
1. This mineralogy cannot explain many unusual properties of the D'' layer, the lowermost ~150 km of the mantle. Here, using ab initio simulations and high-pressure experiments we show that at pressures and temperatures of the D'' layer, MgSiO 3 transforms from perovskite into a layered CaIrO 3 –type structure (space group Cmcm). The elastic properties of(More)
Post-aragonite phase of CaCO 3 , experimentally known to be stable above 40 GPa [, is believed to be a major carbon-containing mineral in the Earth's mantle. Crystal structure of this mineral phase could not be solved using experimental data or traditional theoretical simulation methods and remained a controversial issue. Using a combination of advanced ab(More)
In situ observations of the perovskite–CaIrO 3 phase transition in MgSiO 3 and in pyrolitic compositions were carried out using a laser-heated diamond anvil cell interfaced with a synchrotron radiation source. For pure MgSiO 3 , the phase boundary between the orthorhombic Mg-perovskite and CaIrO 3-type phases in the temperature range of 1300–3100 K was(More)
Carbonates are important constituents of marine sediments and play a fundamental role in the recycling of carbon into the Earth's deep interior via subduction of oceanic crust and sediments. Study of the stability of carbonates under high pressure and temperature is thus important for modelling the carbon budget in the entire Earth system. Such studies,(More)
Keywords: post-magnesite density functional theory ab initio simulations crystal structure prediction evolutionary algorithm high pressure Most of the oxidized carbon in the Earth's lower mantle is believed to be stored in the high-pressure forms of MgCO 3 and/or CaCO 3 or possibly even CO 2. Recently, through ab initio evolutionary simulations and(More)
Using ab initio simulations and high-pressure experiments in a diamond anvil cell, we show that alumina (Al(2)O(3)) adopts the CaIrO(3)-type structure above 130 GPa. This finding substantially changes the picture of high-pressure behavior of alumina; in particular, we find that perovskite structure is never stable for Al(2)O(3) at zero Kelvin. The(More)