Professor Natalia Dubrovinskaia
Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography
University of Bayreuth, Bayreuth
In a science fiction novel published by Jules Verne in 1864, travelers to the center of the Earth encountered “crystals…like globes of light”. One and a half century later, studies of crystals compressed to enormous pressure exceeding millions of atmospheres shed light on the inner Earth.
The Earth’s deep interior is largely inaccessible. The deepest hole bored at the Kola Peninsula in Russia is of only about 12 km out of 6370 km of the Earth’s radius. Our present understanding is based on indirect inferences. These include the average chemical composition of the solar system, the chemical composition of rocks near the Earth’s surface, geophysical measurements of the Earth’s density and of the seismic wave-velocity distribution, and laboratory studies of the state and properties of materials at high pressures and temperatures.
Since the invention in the late 1950s, the diamond anvil cell (DAC) technique became the major tool for materials investigations at extreme pressure-temperature conditions. Samples of less than 0.1 mm across are compressed between the tips of gem-quality diamonds. X-rays and lasers are fired through the diamond anvils at the samples to heat them and investigate their chemical and phase state, and their properties. The DAC technique provided researchers with the opportunity for in situ studying of matter at pressures extended above 300 GPa using a wide range of spectroscopic, elastic and inelastic scattering methods. Development of synchrotron X-ray sources, fast and sensitive area detectors, as well as building of synchrotron beamlines specializing in high-pressure diffraction experiments have brought significant progress to high-pressure crystallography, enabling researchers to couple DACs with low- and high-temperature facilities (e.g. cryostats and laser heating systems), to work with very tiny samples (as small as a few micrometers), and to investigate complex solids.
„Traveling” along the thermodynamic path through the inner Earth conditions and investigations of a number of oxides, silicates, carbonates, and alloys, which are expected to be found in Earth’s mantle and core, enabled a number of unexpected findings which affect our understanding of how our planet is functioning, how processes in the interiors are linked to the events on the Earth surfaces, including global climatic changes and mass extinctions.