Energies of the phases of ice at low temperature and pressure relative to ice Ih

1988 ◽  
Vol 66 (4) ◽  
pp. 919-924 ◽  
Author(s):  
Y. Paul Handa ◽  
D. D. Klug ◽  
Edward Whalley
Keyword(s):  
High Pressure ◽  
Heat Flow ◽  
Low Temperature ◽  
Ambient Pressure ◽  
High Pressure Phase ◽  
Flow Calorimeter ◽  
Heat Flow Calorimeter ◽  
Temperature And Pressure ◽  
Pressure Phase

The enthalpy of transformation to ice Ic of ice II, IX, V, VI, and VIII that have been recovered at 77 K and ambient pressure, and of the transformation of ice Ic to Ih, has been measured in a heat-flow calorimeter. The enthalpy of transformation of ice Ic to Ih depends on the high-pressure phase used to make the ice Ic. The thermodynamics of the transformation of ice IX, which was made by cooling ice III at 0.3–0.7 K s−1, to ice III shows that the ice IX was fully orientationally ordered to the precision of the experiments.

High-Pressure Synthesis and Crystal Structure of the New Orthorhombic Polymorph β-HgB4O7

2005 ◽  
Vol 60 (8) ◽  
pp. 815-820 ◽  
Author(s):  
Holger Emme ◽  
Matthias Weil ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Ambient Pressure ◽  
Normal Pressure ◽  
High Pressure Phase ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
High Pressure Synthesis ◽  
Pressure Synthesis ◽  
Pressure Phase

The new orthorhombic polymorph β-HgB4O7 has been synthesized under high-pressure and hightemperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 600 °C. β-HgB4O7 is isotypic to the known ambient pressure phases MB4O7 (M = Sr, Pb, Eu) and the high-pressure phase β-CaB4O7 crystallizing with two formula units in the space group Pmn21 with lattice parameters a = 1065.6(2), b = 438.10(9), and c = 418.72(8) pm. The relation of the crystal structure of the high-pressure phase β-HgB4O7 to the normal pressure phase α-HgB4O7 as well as the relation to the isotypic phases MB4O7 (M = Sr, Pb, Eu) and β-CaB4O7 are discussed.

Low-temperature and high-pressure phase changes of room-temperature ionic liquids

2020 ◽  
Vol 300 ◽  
pp. 112340
Author(s):  
Hiroshi Abe ◽  
Hiroaki Kishimura ◽  
Takahiro Takekiyo ◽  
Tomonori Hanasaki ◽  
Yukihiro Yoshimura ◽  
...  
Keyword(s):  
High Pressure ◽  
Ionic Liquids ◽  
Low Temperature ◽  
Room Temperature ◽  
Phase Changes ◽  
High Pressure Phase ◽  
Room Temperature Ionic Liquids ◽  
Pressure Phase

LEAD-CHALCOGENIDES UNDER PRESSURE: AB-INITIO STUDY

2013 ◽  
Vol 22 ◽  
pp. 612-618 ◽  
Author(s):  
DINESH C. GUPTA ◽  
IDRIS HAMID
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Ab Initio ◽  
Band Gap ◽  
Rock Salt ◽  
High Pressures ◽  
Ambient Pressure ◽  
High Pressure Phase ◽  
Lead Chalcogenides ◽  
Pressure Phase

ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.

Zur Kenntnis der Hochdruckphase BaAl2/ On BaAl2, a High Pressure Phase

1984 ◽  
Vol 39 (4) ◽  
pp. 421-423 ◽  
Author(s):  
Gerhard Cordier ◽  
Erwin Czech ◽  
Herbert Schäfer
Keyword(s):  
High Pressure ◽  
High Pressure Phase ◽  
Standard Temperature ◽  
Temperature And Pressure ◽  
Pressure Phase

At 30 kbar and 1000 °C in the Ba/Al-system the compound BaAl2 exists, which remains metastable under standard temperature and pressure after quenching. The new compound crystallizes in the MgCu2-type with a = 870.2(5) pm.

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