M. Hanfland

Pressure-induced successive structural transitions and high-pressure tetragonal phase of Fe1.08Te

We report the effects of hydrostatic pressure on the temperature-induced phase transitions in Fe1.08Te in the pressure range 0-3 GPa using synchrotron powder x-ray diffraction (XRD). The results reveal a plethora of phase transitions. At ambient pressure, Fe1.08Te undergoes simultaneous first-order structural symmetry-breaking and magnetic phase transitions, namely from the paramagnetic tetragonal (P4/nmm) to the antiferromagnetic monoclinic (P2_1/m) phase. We show that, at a pressure of 1.33 GPa, the low temperature structure adopts an orthorhombic symmetry. More importantly, for pressures of 2.29 GPa and higher, a symmetry-conserving tetragonal-tetragonal phase transition has been identified from a change in the c/a ratio of the lattice parameters. The succession of different pressure and temperature-induced structural and magnetic phases indicates the presence of strong magneto-elastic coupling effects in this material.

Equation of state of lithium to 21 GPa

Abstract The equation of state of lithium has been measured up to 21xa0GPa ( T=298 K ) using diamond anvil cell techniques and high-resolution angle-dispersive synchrotron X-ray diffraction. The b.c.c.–f.c.c. transition has been observed near 7.5xa0GPa. The volume change at the transition amounts to only 0.16(3)%. These results basically confirm earlier diffraction studies up to 10xa0GPa by Olinger and Shaner. Total energy calculations were performed using the full-potential linearized augmented-plane-wave method. Good overall agreement is found between calculated pressure–volume relations and the experimental data. At twofold compression the calculated repulsion is too strong. We have observed that pure Li, if in direct contact with diamond anvils, develops a corrosive effect on the anvils at pressures above 20xa0GPa.

The crystal structure of rubidium-VI near 50 GPa

Abstract The crystal structure of the high-pressure phase rubidium-VI (Rb-VI) has been investigated near 50xa0GPa using monochromatic synchrotron X-ray diffraction. Full profile refinements of powder diffraction data resulted in a solution with space group Cmca and 16 atoms in the orthorhombic unit cell. The phase Rb-VI is isostructural to the recently determined oC 16 structures of the high-pressure phases Cs-V and Si-VI. Similar to the case of cesium, the oC 16 structure of Rb appears at a pressure, where the electronic s→d transition is thought to be essentially completed.

Pressure-induced Oxidation State Change of Ytterbium in YbGa2

The crystal structure and the electronic properties of YbGa2 realising a CaIn2 type atomic arrangement were characterised at ambient conditions using single crystal X-ray diffraction data and magnetic susceptibility measurements at ambient pressure. Pressure-induced changes of structural and electronic properties of YbGa2 were measured by means of angle-dispersive X-ray powder diffraction and XANES at the Yb LIII threshold. At pressures above 22(2)u200aGPa, YbGa2 undergoes a structural phase transition into a high pressure modification with a UHg2 type crystal structure. Parallel toxa0the pressure-induced structural alterations, ytterbium in YbGa2 undergoes an increase of the oxidation state from +2u200aat ambient conditions to +3 in the high-pressure phase. Quantum chemical calculations of the Electron-Localisation-Function confirm that the phase transition is associated with a conversion of the three-dimensional gallium network of the low-pressure crystal structure into two-dimensional gallium layers in the high-pressure modification. n n n nDruckinduzierte Anderung der Oxidationstufe von Ytterbium im YbGa2 n n n nDie Kristallstruktur und die elektronischen Eigenschaften von YbGa2, das eine Kristallstruktur vom CaIn2 Typ realisiert, wurden bei Normaldruck mittels Einkristallstrukturanalyse und Messungen der magnetischen Suszeptibilitat charakterisiert. Druckinduzierte Anderungen von strukturellen und magnetischen Eigenschaften wurden durch Messungen winkeldispersiver Rontgenpulverdiagramme und XANES and der Ybu200aLIII Kante bestimmt. Bei Drucken oberhalb von 22(2)u200aGPa wandelt sich YbGa2 in eine Hochdruckmodifikation mit einer Kristallstruktur vom UHg2-Typ um. Parallel zu den strukturellen Anderungen erhoht sich die Oxidationsstufe des Ytterbiums in YbGa2 von +2 bei Normaldruck auf +3 in der Hochdruckphase. Quantenchemische Berechnungen der Elektronen-Lokalisierungs-Funktion bestatigen, dass der Phasenubergang mit einer Umwandlung des dreidimensionalen Galliumnetzwerks der Niederdruckstruktur in zweidimensionale Galliumnetze der Hochdruckmodifikation verbunden ist.

Effect of pressure on the magnetostructural transition in SrFe2As2

We present a systematic pressure study of poly- and single-crystalline

The effect of pressure on the excimer luminescence of 9-cyanoanthracene

{text{SrFe}}_{2}{text{As}}_{2}

Metallic state in cubic FeGe beyond its quantum phase transition

by electrical-resistivity and x-ray-diffraction measurements.

Structural phase transition of GdGa2 at high pressure

{text{SrFe}}_{2}{text{As}}_{2}

Crystal structure of LaTiO3.41 under pressure

exhibits a structural phase transition from a tetragonal to an orthorhombic phase at

Graphite and graphite intercalation compounds under pressure: Raman modes, optical reflectivity, and phase changes

{T}_{0}=205text{ }text{K}