Structural phase transitions of Pb-adsorbed Si(111) surfaces at low temperatures

A novel one-dimensional perovskite-type hybrid compound (trimethylamine N-oxide)CdCl3 exhibited the sensitivity of dielectric switches at high and low temperatures.

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Thermodynamical properties ofK2OsCl6andK2ReCl6at low temperatures and near their structural phase transitions

Physical Review B ◽

10.1103/physrevb.15.382 ◽

1977 ◽

Vol 15 (1) ◽

pp. 382-387 ◽

Cited By ~ 10

Author(s):

Vladimir Novotny ◽

Carlos A. Martin ◽

Robin L. Armstrong ◽

Peter P. M. Meincke

Keyword(s):

Phase Transitions ◽

Low Temperatures ◽

Structural Phase ◽

Structural Phase Transitions ◽

Thermodynamical Properties

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Structural phase transitions of HfV2 at low temperatures

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768100003633 ◽

2000 ◽

Vol 56 (4) ◽

pp. 601-606 ◽

Cited By ~ 9

Author(s):

Yusheng Zhao ◽

Fuming Chu ◽

Robert B. Von Dreele ◽

Qing Zhu

Keyword(s):

Phase Transitions ◽

Low Temperatures ◽

Structural Phase ◽

Orthorhombic Phase ◽

Unit Cell ◽

The Body ◽

Cubic Phase ◽

Face Centered Cubic ◽

Structural Phase Transitions ◽

Low Symmetry

We report a high-resolution synchrotron X-ray powder diffraction study on HfV2, hafnium divanadium, at low temperatures. In this work we show, for the first time, a complete sequence of structural phase transitions of HfV2 from cubic (Fd3m) to tetragonal (I41/amd) to orthorhombic (Imma) in succession as temperature decreases. Peak splitting and extra diffraction peaks owing to lattice distortion can be clearly distinguished for the low-symmetry phases. The atomic positions and lattice parameters were obtained by Rietveld refinement. The bond lengths and angles of the HfV2 crystal structure at the low-symmetry phases were correctly determined from the structure refinement. The face-centered cubic (Fd3m) unit cell (Z = 24) transforms to a body-centered tetragonal (I41/amd) phase with a 45° rotation relative to the cubic cell and with a reduced number of atoms (Z = 12) in the unit cell at a temperature of T = 112 K. The orthorhombic phase occurs at T = 102 K and it keeps the body-centered symmetry (Imma) and Z = 12 in the unit cell. The refinement results indicate that there may be a small amount of untransformed cubic phase left over in the lower symmetry phases. The abnormal thermal contraction of both tetragonal phase and orthorhombic phase marks the significance of structural change in HfV2.

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Crystallographic data of new superlattice phases for spinel LiMn2O4 at low temperatures

Powder Diffraction ◽

10.1017/s0885715600010770 ◽

2000 ◽

Vol 15 (1) ◽

pp. 19-22 ◽

Cited By ~ 9

Author(s):

Hiroshi Hayakawa ◽

Toshimi Takada ◽

Hirotoshi Enoki ◽

Etsuo Akiba

Keyword(s):

Phase Transitions ◽

Low Temperatures ◽

Room Temperature ◽

Structural Phase ◽

Unit Cell ◽

Structural Phase Transitions ◽

X Ray Diffraction ◽

Spinel Limn2o4 ◽

X Ray ◽

Face Centered

Extensive analyses of low-temperature powder x-ray diffraction data for spinel LiMn2O4 (Fd3¯m at room temperature) make it clear that two structural phase transitions occur: first around 285 K from cubic to orthorhombic, second around 65 K from orthorhombic to tetragonal. At temperatures under 285 K, superlattice peaks appear in the diffraction pattern that were successfully indexed by tripling the a and b axes of the spinel unit cell. At 250 K, the unit cell is face-centered orthorhombic, Fddd, F2dd, or Fd2d, with a=24.855(1), b=24.755(2), c=8.2014(3) Å, V=5046.1(4) Å3, Dx=4.284 g/cm3, Z=72. The unit cell at 30 K was confirmed to be body-centered tetragonal I41/amd or I41/a, with a=17.5176(3), c=8.1961(2) Å, V=2515.1(1) Å3, Dx=4.298 g/cm3, Z=36.

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