The high-pressure structure of (1-x)Na Bi TiO -xBaTiO at the morphotropic phase boundary.

The pressure-induced structural changes in the perovskite-type (ABO ) ferroelectric solid solution (1-x)Na Bi TiO -xBaTiO (NBT-xBT) at the morphotropic phase boundary (MPB) ( ) have been analyzed up to 12.3 GPa by single-crystal x-ray diffraction with synchrotron radiation. A pressure-induced phase transition takes place between 4.

Inclusions in diamonds probe Earth's chemistry through deep time.

Most of our knowledge about the chemical composition of the Earth’s interior is primarily retrieved by indirect observations, experiments and calculations that are limited to simple compositions. Here, the authors present the investigation of inclusions trapped in super deep diamonds as an alternative source of a wealth of information on the chemical state of the Earth’s interior through time.

The contribution of elastic geothermobarometry to the debate on HP versus UHP metamorphism.

Characterizing the pressure and temperature () histories of eclogite facies rocks is of key importance for unravelling subduction zone processes at all scales. Accurate estimates provide constraints on tectonic and geochemical processes affecting subduction dynamics and help in interpreting the geophysical images of present-day converging plates. Conventional equilibrium geothermobarometers are challenged in ultra high pressure (UHP) metamorphic terranes, as minerals may undergo re-equilibration along their exhumation path.

Accurate structures and energetics of neutral-framework zeotypes from dispersion-corrected DFT calculations.

Density-functional theory (DFT) calculations incorporating a pairwise dispersion correction were employed to optimize the structures of various neutral-framework compounds with zeolite topologies. The calculations used the PBE functional for solids (PBEsol) in combination with two different dispersion correction schemes, the D2 correction devised by Grimme and the TS correction of Tkatchenko and Scheffler. In the first part of the study, a benchmarking of the DFT-optimized structures against experimental crystal structure data was carried out, considering a total of 14 structures (8 all-silica zeolites, 4 aluminophosphate zeotypes, and 2 dense phases).

Experimental and ab Initio Study of Catena(bis(μ2-iodo)-6-methylquinoline-copper(I)) under Pressure: Synthesis, Crystal Structure, Electronic, and Luminescence Properties.

Copper(I) iodine compounds can exhibit interesting mechanochromic and thermochromic luminescent properties with important technological applications. We report the synthesis and structure determination by X-ray diffraction of a new polymeric staircase copper(I) iodine compound catena(bis(μ2-iodo)-6-methylquinoline-copper(I), [C10H9CuIN]. The structure is composed of isolated polymeric staircase chains of copper-iodine coordinated to organic ligands through Cu-N bonds.

High-pressure crystal structure of elastically isotropic CaTiO3 perovskite under hydrostatic and non-hydrostatic conditions.

The structural evolution of orthorhombic CaTiO3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa.

The structural state of lead-based relaxor ferroelectrics under pressure.

The exceptional properties of lead-based perovskite-type (ABO(3)) relaxor ferroelectrics are due to their structural inhomogeneities. At ambient conditions, the average structure is pseudocubic but rich in ferroic nanoregions too small to be directly studied by conventional diffraction analysis. However, combining in situ temperature and pressure diffraction and Raman scattering allows us to resolve the structural complexity of relaxors.

Octahedral tilts, symmetry-adapted displacive modes and polyhedral volume ratios in perovskite structures.

The structures of tilted perovskites in each of the 15 tilt systems have been decomposed into the amplitudes of symmetry-adapted modes in order to provide a clear and unambiguous definition of the tilt angles. A full expression in terms of the mode amplitudes for the ratio of the volumes of the two polyhedra within the perovskite structure for each of the 15 tilt systems is derived, along with more general expressions in terms of either mode amplitudes or tilt angles that can be used to estimate this ratio when the distortions of the octahedra are small.

Comparison between beryllium and diamond-backing plates in diamond-anvil cells: application to single-crystal x-ray diffraction high-pressure data.

A direct comparison between two complete intensity datasets, collected on the same sample loaded in two identical diamond-anvil pressure cells equipped, respectively, with beryllium and diamond-backing plates was performed. The results clearly demonstrate that the use of diamond-backing plates significantly improves the quality of crystal structure data. There is a decrease in the internal R factor for averaging, structure refinement agreement factors, and in the errors and uncertainties of the atomic coordinates, atomic displacement parameters, and individual bond lengths.

The structural variation of rhombohedral LaAlO3 perovskite under non-hydrostatic stress fields in a diamond-anvil cell.

The structural variation of LaAlO(3) perovskite under non-hydrostatic stress developed in the pressure medium within a diamond-anvil cell was determined using single-crystal x-ray diffraction. The experimental results show that the lattice of LaAlO(3) becomes more distorted and deviates from the hydrostatic behavior as pressure is increased up to 7.5 GPa.

Detailed study of the phase transition in [Ni(H2O)6](NO3)2·(15-crown-5)·H2O and analysis in terms of mean-field theory.

The transition between 190 and 200 K in [Ni(H(2)O)(6)](NO(3))(2)·(15-crown-5)·H(2)O has been followed by determining the structure at 22 temperatures in the range 90-273 K. The structural change is a zone-boundary transition with a critical point at (½, 0, ½) in the Brillouin zone of the high-temperature phase; both phases have space-group symmetry P2(1) but the volume of the unit cell is halved when a crystal is heated through the transition. The only obvious disorder in the high-temperature phase is of the lattice water molecule, which occupies two sites; some disorder persists below the transition.

Octahedral tilting in Pb-based relaxor ferroelectrics at high pressure.

We have employed a combination of powder neutron diffraction and single-crystal synchrotron X-ray diffraction to characterize the pressure-induced phase transitions that occur in the perovskite-type relaxor ferroelectric PbSc(0.5)Ta(0.5)O(3) (PST) and Pb(0.

High-pressure crystallography of rhombohedral PrAlO(3) perovskite.

The evolution of the crystal structure of rhombohedral PrAlO(3) perovskite with pressure has been investigated by single-crystal x-ray diffraction and Raman scattering experiments. The structural evolution as indicated by lattice strains, octahedral tilts, and the distortions of the octahedral AlO(6) and polyhedral PrO(12) groups with increasing pressure, is controlled by the relative compressibilities of the AlO(6) octahedra and the PrO(12) site. Because the AlO(6) octahedra are more compressible than the PrO(12) sites, up to 7.

Pressure-induced cooperative bond rearrangement in a zinc imidazolate framework: a high-pressure single-crystal X-ray diffraction study.

The pressure-dependent structural evolution of a neutral zinc-imidazolate framework [Zn(2)(C(3)H(3)N(2))(4)](n) (ZnIm) has been investigated. The as-synthesized three-dimensional ZnIm network (alpha-phase) crystallizes in the tetragonal space group I4(1)cd (a = 23.5028(4) A, c = 12.

Disorder and pseudo-symmetry in octakis(trivinylsilyl)octasilicate.

Octakis(trivinylsilyl)octasilicate was prepared by capping octaspherosilicate cubes, [Si(8)O(20)](8-), with trivinylsilyl groups in methanol solution. Crystals grown from CCl(4) crystallize in the tetragonal space group I4(1). Systematic absences are consistent with the space group I4(1)/amd, although the R(int) values clearly indicate 4/m rather than 4/mmm Laue symmetry.

High-pressure- and low-temperature-induced changes in [(CH3)2NH(CH2)2NH3][SbCl5].

The structure of N,N-dimethylethylenediammonium pentachloroantimonate(III), [(CH3)2NH(CH2)2NH3][SbCl5], NNDP, was investigated at 100 and 15 K at ambient pressure, as well as at pressures up to 4.00 GPa at room temperature in the diamond-anvil cell. The stable structure at low temperatures and low pressures consists of isolated [SbCl5]2- anions and [(CH3)2NH(CH2)2NH3]2+ cations.

Single-crystal synchrotron X-ray diffraction study of wüstite and magnesiowüstite at lower-mantle pressures.

This study demonstrates the use of monochromatic synchrotron X-ray radiation of 40 keV for high-precision equation-of-state studies on sets of single crystals analysed individually in the same diamond-anvil pressure cell. Angle-dispersive zone-axis diffraction patterns were obtained from crystals of wustite-Fe0.93O and magnesiowüstite-(Mg0.