What is the structure of La3Ni2O7 at high pressure?
Best insight from top research papers
At high pressure, La3Ni2O7 exhibits an orthorhombic structure of the Fmmm space group. The superconducting phase in La3Ni2O7 under high pressure is characterized by the strong interaction between the 3d_(x^2-y^2) and 3d_(z^2) orbitals of Ni cations with the oxygen 2p orbitals. Density functional theory calculations suggest that superconductivity emerges concurrently with the metallization of the σ-bonding bands under the Fermi level, which consist of the 3d_(z^2) orbitals interacting with the apical oxygens connecting Ni-O bilayers. This structural information provides crucial insights into the high-Tc superconductivity observed in La3Ni2O7 at elevated pressures, offering a new avenue for investigating superconductivity mechanisms in this compound.
Answers from top 5 papers
More filters
| Papers (5) | Insight |
|---|---|
| The high-pressure phase of La$_3$Ni$_2$O$_7$ exhibits charge ordering and a single active $3d_{z^2}$ orbital per unit cell, influenced by nonlocal correlation and screening effects. | |
16 May 2023 2 Citations | At high pressure, La3Ni2O7 exhibits an orthorhombic structure of Fmmm space group, with Ni cations' 3d_(x^2-y^2) and 3d_(z^2) orbitals strongly interacting with oxygen 2p orbitals. |
13 Jun 2023 | The high-pressure phase of La$_3$Ni$_2$O$_7$ features a single active $3d_{z^2}$ orbital per unit cell, with charge ordering and nonlocal correlation effects influencing its electronic structure. |
| At high pressure, La3Ni2O7 exhibits a transition to a superconducting phase with a resistance drop at ~50% around 70 K, evolving into a kink-like anomaly at pressures above 40 GPa. | |
16 May 2023 | At high pressure, La3Ni2O7 adopts an orthorhombic structure with an Fmmm space group, where Ni cations' 3d orbitals interact strongly with oxygen 2p orbitals, facilitating superconductivity. |
Related Questions
Why is Ni used in layered transition metal oxides?5 answersNi is utilized in layered transition metal oxides due to its advantageous properties for battery applications. Nickel-rich layered oxides offer high specific capacity and low cost, making them promising cathode materials for high-energy-density lithium-ion batteries. However, challenges such as structural instability and capacity fading exist, hindering their commercialization. To address these issues, research focuses on enhancing the surface reactivity and stability of Ni-rich materials through innovative approaches like surface modifications and element doping. These strategies aim to improve the structural stability, eliminate impurities, and enhance the reversibility of phase transitions, ultimately boosting the performance and longevity of Ni-based cathode materials for advanced battery technologies.
Does high entropy alloy has higher microstructural stability than nickel-based superalloy?5 answersHigh entropy alloys (HEAs) exhibit varying degrees of microstructural stability compared to nickel-based superalloys. While some HEAs like Ni-Co-based HEA display a hierarchical microstructure with good yield strength and strain rate insensitivity, others may undergo phase decomposition during creep, leading to instability. The thermal stability of HEAs can be influenced by factors like cooling rate, thermal exposure, and eutectic morphology, affecting the precipitation behavior and mechanical properties. Additionally, the microstructure of refractory HEAs can undergo phase separation at lower temperatures, but both single-phase metastable and as-cast states show comparable mechanical properties, suggesting practical applicability. Therefore, the microstructural stability of HEAs compared to nickel-based superalloys varies depending on the specific alloy composition and processing conditions.
What is the high pressure iron phase?4 answersThe high-pressure phase of iron is still a topic of debate. Some studies suggest that iron undergoes a phase transition to a hexagonal close-packed (hcp) structure at high pressures, while others propose that it remains in a body-centered cubic (bcc) structure. Nanocrystalline Fe confined by single-walled carbon nanohorns (SWCNHs) and SWCNHs filled with Fe nanoparticles exhibited a reversible transformation from bcc Fe to hcp Fe at 11.7 GPa. Iron carbonitrides with diverse structures, such as Fe7C3-type Fe7(C, N)3, may be the main host for nitrogen in the deep mantle. The instability of the iron nitride γ′-Fe4N with respect to other phases at high pressure is well established, but the actual type of phase transitions and equilibrium conditions are still poorly investigated. The crystal structure of iron in the Earth's inner core is unknown, but computational studies suggest that the bcc phase may be stabilized prior to melting at high pressures. Under high pressure and temperature, α-Fe remains ferromagnetic, while pure γ-Fe and ε-Fe do not exhibit magnetic response.
What is high entropy oxide?4 answersHigh entropy oxides are a class of materials that utilize configurational entropy for material synthesis. These materials have unique physiochemical properties and show promise in various fields such as chemical sensing, electronics, and catalysis. High entropy oxides can be used as electrode materials for supercapacitors, and efforts have been made to increase their energy density while enhancing specific capacitance. Transition metal elements such as Fe, Co, Cr, Mn, and Ni are selected to prepare high entropy oxides, and the calcination temperature plays a crucial role in determining their structural morphology and electrochemical performance. High entropy oxides have also been explored for their potential in lithium-sulfur batteries, where they act as polysulfide adsorbents and catalysts for redox reactions. These materials exhibit excellent discharge capacity, high rate capability, and long-term cycling stability, making them promising for efficient LSB technology. Additionally, high entropy perovskite oxides have shown high catalytic activity for the oxygen evolution reaction (OER), making them attractive for electrochemical energy storage applications. The multi-cation composition in high entropy oxides contributes to their superior OER activity, surpassing that of their parent compounds.
Why is positively correlated with Ni3 content?5 answersThe increase in Ni3+ content is positively correlated with the transition of LaNiO3-δ films from a semi-conductive behavior to an electronic conductor. The higher Ni3+/Ni2+ ratio in the films leads to a reduction in the electron-phonon interaction, a shortened mean free path, and an increased electron-electron coupling. This correlation suggests that the changes in the valence states of Ni in the films affect their transport properties.
What are the structures of small nickel cations with ethanol in the gas phase?5 answersSmall nickel cations in the gas phase form various structures when interacting with ethanol. The structures of these cations have been studied using different techniques. The structures of homoleptic nickel carbonyl cluster cations, including dinuclear Ni2(CO)7+ and Ni2(CO)8+, trinuclear Ni3(CO)9+, and tetranuclear Ni4(CO)11+, have been determined using infrared photodissociation spectroscopy and density functional calculations. Layered and acid-activated clays, used as catalytic support, have been investigated for their structural and catalytic properties in the gas-phase total oxidation of ethanol. The pillaring, acidic treatments, and nickel loading are the main factors affecting the textural, structural, and catalytic properties of the clay. Small tantalum cluster cations have also been studied in the gas phase, and the reaction pathways with alcohols, including ethanol, have been observed. The branching ratios for the reaction depend on the cluster size, with a minimum of OH abstraction occurring for Ta7+. The geometric structures of small cationic rhodium clusters have been investigated using experimental and computational methods, and the clusters were found to favor structures based on octahedral and tetrahedral motifs.