scholarly journals Superconductivity in room-temperature stable electride and high-pressure phases of alkali metals

2015 ◽  
Vol 373 (2037) ◽  
pp. 20140450 ◽  
Author(s):  
Hideo Hosono ◽  
Sung-Wng Kim ◽  
Satoru Matsuishi ◽  
Shigeki Tanaka ◽  
Atsushi Miyake ◽  
...  
Keyword(s):  
High Pressure ◽  
Fermi Energy ◽  
Electronic Structures ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Superconducting Phase ◽  
Alkaline Earth Metals ◽  
Superconducting Transition

S-band metals such as alkali and alkaline earth metals do not undergo a superconducting transition (SCT) at ambient pressure, but their high-pressure phases do. By contrast, room-temperature stable electride [Ca 24 Al 28 O 64 ] 4+ ⋅4e − (C12A7:e − ) in which anionic electrons in the crystallographic sub-nanometer-size cages have high s-character exhibits SCT at 0.2–0.4 K at ambient pressure. In this paper, we report that crystal and electronic structures of C12A7:e − are close to those of the high-pressure superconducting phase of alkali and alkaline earth metals and the SCT of both materials is induced when electron nature at Fermi energy ( E F ) switches from s- to sd-hybridized state.

scholarly journals Stoichiometric evolutions of PH3 under high pressure: implication for high-Tc superconducting hydrides

2019 ◽  
Vol 6 (3) ◽  
pp. 524-531 ◽  
Author(s):  
Ye Yuan ◽  
Yinwei Li ◽  
Guoyong Fang ◽  
Guangtao Liu ◽  
Cuiying Pei ◽  
...  
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Recent Observation ◽  
Theoretical Calculations ◽  
Ambient Pressure ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
Elemental Phosphorus ◽  
High Tc ◽  
X Ray

Abstract The superconductivity of hydrides under high pressure has attracted a great deal of attention since the recent observation of the superconducting transition at 203 K in strongly compressed H2S. It has been realized that the stoichiometry of hydrides might change under high pressure, which is crucial in understanding the superconducting mechanism. In this study, PH3 was studied to understand its superconducting transition and stoichiometry under high pressure using Raman, IR and X-ray diffraction measurements, as well as theoretical calculations. PH3 is stable below 11.7 GPa and then it starts to dehydrogenate through two dimerization processes at room temperature and pressures up to 25 GPa. Two resulting phosphorus hydrides, P2H4 and P4H6, were verified experimentally and can be recovered to ambient pressure. Under further compression above 35 GPa, the P4H6 directly decomposed into elemental phosphorus. Low temperature can greatly hinder polymerization/decomposition under high pressure and retains P4H6 up to at least 205 GPa. The superconductivity transition temperature of P4H6 is predicted to be 67 K at 200 GPa, which agrees with the reported result, suggesting that it might be responsible for superconductivity at higher pressures. Our results clearly show that P2H4 and P4H6 are the only stable P–H compounds between PH3 and elemental phosphorus, which is helpful for shedding light on the superconducting mechanism.

scholarly journals Interactions Between Zinc Oxide and Alkali Metals, Alkaline Earth Metals and Halogens: A Theoretical Study

2017 ◽  
Vol 29 (3) ◽  
pp. 585-588
Author(s):  
Aned de Leon ◽  
Grace Jouanne-Jeraissati ◽  
Agustín Martínez-Contreras
Keyword(s):  
Zinc Oxide ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Theoretical Study ◽  
Alkaline Earth Metals

PRESSURE-INDUCED ELECTRONIC PHASE TRANSITIONS AND SUPERCONDUCTIVITY IN TITANIUM

2009 ◽  
Vol 23 (05) ◽  
pp. 723-741 ◽  
Author(s):  
K. IYAKUTTI ◽  
C. NIRMALA LOUIS ◽  
S. ANURATHA ◽  
S. MAHALAKSHMI
Keyword(s):  
High Pressure ◽  
Band Structure ◽  
Fermi Surface ◽  
High Pressures ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Normal Pressure ◽  
Orbital Method ◽  
Superconducting Transition ◽  
Electronic Band

The electronic band structure, density of states, structural phase transition, superconducting transition and Fermi surface cross section of titanium ( Ti ) under normal and high pressures are reported. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s → d transition. On the basis of band structure and total energy results obtained using tight-binding linear muffin-tin orbital method (TB LMTO), we predict a phase transformation sequence of α( hcp ) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis, we predict a δ (distorted bcc) phase which is not stable at any high pressures. At ambient pressure, the superconducting transition occurs at 0.354 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp–Ti . On further increase of pressure, Tc begins to decrease at a rate of 1.464 K/Mbar. The highest value of Tc(P) estimated is 5.043 K for hcp–Ti , 4.538 K for ω– Ti and 4.85 K for bcc – Ti . From this, it is inferred that the maximum value of Tc(P) is rather insensitive to the crystal structure of Ti . The nonlinearities in Tc(P) is explained by considering the destruction and creation of new parts of Fermi surface at high pressure. At normal pressure, the hardness of Ti is in the following order: ω- Ti > hcp - Ti > bcc- Ti > γ- Ti .

scholarly journals High-Pressure Structural Behavior and Equation of State of Kagome Staircase Compound, Ni3V2O8

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 910
Author(s):  
Daniel Diaz-Anichtchenko ◽  
Robin Turnbull ◽  
Enrico Bandiello ◽  
Simone Anzellini ◽  
Daniel Errandonea
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Density Functional ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
A Chain

We report on high-pressure synchrotron X-ray diffraction measurements on Ni3V2O8 at room-temperature up to 23 GPa. According to this study, the ambient-pressure orthorhombic structure remains stable up to the highest pressure reached in the experiments. We have also obtained the pressure dependence of the unit-cell parameters, which reveals an anisotropic compression behavior. In addition, a room-temperature pressure–volume third-order Birch–Murnaghan equation of state has been obtained with parameters: V0 = 555.7(2) Å3, K0 = 139(3) GPa, and K0′ = 4.4(3). According to this result, Ni3V2O8 is the least compressible kagome-type vanadate. The changes of the crystal structure under compression have been related to the presence of a chain of edge-sharing NiO6 octahedral units forming kagome staircases interconnected by VO4 rigid tetrahedral units. The reported results are discussed in comparison with high-pressure X-ray diffraction results from isostructural Zn3V2O8 and density-functional theory calculations on several isostructural vanadates.

HEAT-TREATMENT INFLUENCE ON THE MAGNETIC AND ELECTRIC PROPERTIES OF HIGH-TcYBa2Cu3O7−δ SUPERCONDUCTOR

1996 ◽  
Vol 10 (20) ◽  
pp. 955-961
Author(s):  
LAUREAN HOMORODEAN ◽  
IULIU POP ◽  
ION BURDOI
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Temperature Dependences ◽  
Magnetic And Electric Properties ◽  
Very High

The changes in the temperature dependences of the magnetic susceptibility and the electrical resistivity of a very-high-T c superconducting YBa 2 Cu 3 O 7−δ sample during the thermal cycling between the liquid-nitrogen temperature and the room temperature are studied. Some singularities corresponding to the superconducting transition, the possible existence of a super-high-temperature superconducting phase and the migration of the oxygen atoms in the Cu-O chains are emphasized on these dependencies.

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