Beryllium configuration with neighbouring oxygen atoms revealed

High-pressure experiments prove 50-year-old theoretical prediction.

In high-pressure experiments at DESY’s X-ray light source PETRA III, scientists have observed a unique configuration of beryllium for the first time: At pressures nearly a million times the average atmospheric pressure, beryllium in a phosphate crystal acquires six neighbouring atoms instead of the usual four. This six-fold coordination had been predicted by theory more than 50 ago, but could not be observed until now in inorganic compounds. DESY scientist Anna Pakhomova and her collaborators report their results in the journal Nature Communications.
“Originally, chemistry textbooks stated that elements like beryllium from the second period of the periodic table could never have more than four neighbours, due to their electron configuration”, explains Pakhomova. “Then around 50 years ago theorists discovered that higher coordinations could actually be possible, but these have adamantly evaded experimental proof in inorganic compounds.” Inorganic compounds are typically those without carbon – apart from a few exceptions like carbon dioxide and carbon monoxide.

>Read more on the PETRA III at DESY website

Image: Transformation of the usual fourfold coordination of beryllium to five- and sixfold with increasing pressure. (Credit: DESY, Anna Pakhomova)

Did plate tectonics aid the development of life on Earth?

The appearance of plate tectonics 2.5 billion years ago, favouring the internal dynamics of the Earth, would have allowed a significant release of oxygen in the atmosphere inducing the development of life on our planet, according to a study published by the journal Geochemical Perspectives.

The Earth’s atmosphere remained anoxic for two billion years after the formation of our planet. Then, its oxygen content increased drastically during a well-identified Great Oxygenation Event. It is generally believed that the release of free oxygen was due to the biosphere itself, in relation with the evolution of life on Earth. An international team of researchers from Laboratoire Magmas et Volcans (Université Clermont-Ferrand, CNRS-IRD-OPGC), Géosciences Montpellier (Université de Montpellier, CNRS), the laboratory Conditions Extrêmes et Matériaux: Haute Température et Irradiation (CNRS), and involving five scientists from the ESRF propose a completely different scenario. Based on the experimental observation of a significant amount of ferric iron in the deep Earth’s mantle, they suggest an ascent toward the Earth’s surface of a primordial oxidised-mantle material, inducing the arrival of oxygen into the atmosphere. The upwelling movements would have been hampered during the Archean eon, which was dominated by floating micro-plates at the Earth’s surface. Then, major mantle mixing started when modern plate tectonics and deep slab subduction were established about 2.5 billion years ago, enabling the release of oxygen to the Earth’s surface.

>Read more on the ESRF website