Suchergebnisse

At high pressures, autoionization - along with polymerization and metallization - is one of the responses of simple molecular systems to a rise in electron density. Nitrosonium nitrate (NO+NO3-), known for this property, has attracted a large interest in recent decades and was reported to be synthesized at high pressure and high temperature from a variety of nitrogen-oxygen precursors, such as N2O4, N2O and N-2-O-2 mixtures. However, its structure has not been determined unambiguously. Here, we present the first structure solution and refinement for nitrosonium nitrate on the basis of single-crystal X-ray diffraction at 7.0 and 37.0 GPa. The structure model (P2(1)/m space group) contains the triple-bonded NO+ cation and the NO3- sp(2)-trigonal planar anion. Remarkably, crystal-chemical considerations and accompanying density-functional-theory calculations show that the oxygen atom of the NO+ unit is positively charged - a rare occurrence when in the presence of a less-electronegative element. ; Funding Agencies|Alexander von Humboldt FoundationAlexander von Humboldt Foundation; Federal Ministry of Education and Research, Germany (BMBF)Federal Ministry of Education & Research (BMBF) [05K19WC1]; Deutsche Forschungsgemeinschaft (DFG)German Research Foundation (DFG) [DU 954-11/1, DU 393-9/2, DU 393-13/1]; DFGGerman Research Foundation (DFG)European Commission [DFG FOR2125, WI1232]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Carbonates containing CO4 groups as building blocks have recently been discovered. A new orthocarbonate, Sr2CO4 is synthesized at 92 GPa and at a temperature of 2500 K. Its crystal structure was determined by in situ synchrotron single-crystal X-ray diffraction, selecting a grain from a polycrystalline sample. Strontium orthocarbonate crystallizes in the orthorhombic crystal system (space group Pnma) with CO4, SrO9 and SrO11 polyhedra as the main building blocks. It is isostructural to Ca2CO4. DFT calculations reproduce the experimental findings very well and have, therefore, been used to predict the equation of state, Raman and IR spectra, and to assist in the discussion of bonding in this compound. ; Funding Agencies|Alexander von Humboldt-StiftungAlexander von Humboldt Foundation; Bundesministerium fur Bildung und ForschungFederal Ministry of Education & Research (BMBF) [05K19WC1]; Deutsche ForschungsgemeinschaftGerman Research Foundation (DFG) [DU 954-11/1, DU 393-9/2, DU 393-13/1, FOR2125, WI1232]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]