Metal-insulator and magnetic transition of NiO at high pressures

Published versio

A self-interaction corrected pseudopotential scheme for magnetic and strongly-correlated systems

Local-spin-density functional calculations may be affected by severe errors when applied to the study of magnetic and strongly-correlated materials. Some of these faults can be traced back to the presence of the spurious self-interaction in the density functional. Since the application of a fully self-consistent self-interaction correction is highly demanding even for moderately large systems, we pursue a strategy of approximating the self-interaction corrected potential with a non-local, pseudopotential-like projector, first generated within the isolated atom and then updated during the self-consistent cycle in the crystal. This scheme, whose implementation is totally uncomplicated and particularly suited for the pseudopotental formalism, dramatically improves the LSDA results for a variety of compounds with a minimal increase of computing cost.Comment: 18 pages, 14 figure

Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding

Within the broad class of multiferroics (compounds showing a coexistence of magnetism and ferroelectricity), we focus on the subclass of "improper electronic ferroelectrics", i.e. correlated materials where electronic degrees of freedom (such as spin, charge or orbital) drive ferroelectricity. In particular, in spin-induced ferroelectrics, there is not only a {\em coexistence} of the two intriguing magnetic and dipolar orders; rather, there is such an intimate link that one drives the other, suggesting a giant magnetoelectric coupling. Via first-principles approaches based on density functional theory, we review the microscopic mechanisms at the basis of multiferroicity in several compounds, ranging from transition metal oxides to organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic frameworks, MOFs)Comment: 22 pages, 9 figure

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Studies on some fast ion conductors

We report diffraction experiments on some representative Fast Ion Conductors. The structures of anhydrous stoichiometric deuterium (DAl11O17) and silver (AgAl 11O17) beta aluminas have each been determined at four temperatures in the range 4 . 2K - 773K using powder neutron diffraction (PND) data. In DAl11O17, a strong D-O(5) hydroxyl linkage is maintained at all four temperatures .For AgAl11O17 at 4.2K,we have observed, for the first time in metal beta aluminas, a completely ordered cation distribution. The material, which was prepared by a new route, is accurately stoichiometric. At 298K,the silver atoms have become somewhat delocalised and by 773K they are organised in a highly diffuse manner. Single crystal neutron diffraction was used to elucidate the proton distributions in ammonium beta alumina, (NH4) 1.25Al11- 017.125, and the two derivatives (NH4) 0.78H0.25Al11017 and 'HA111- 017.In the parent compound, the positions and orientations of the two independant (NH+4) species are such that all protons are involved in favourable hydrogen-bonding schemes. In formation of the first derivative, one of these sites becomes completely depopulated. Our results clarify the thermal behaviour of (NH4) 1.25Al11017.125 and we propose schemes by which stoichiometric beta aluminas are formed from this precursor and the related (H30)1+x- Al11017.+x/2. The crystal structures of I-Ag3PO4(25°C and 375°C) , II-Ag3PO4(650°C) ,II-Na3PO4 (γ) (400°C) and the solid solutions Na3(1-x)AlxPO4are described. The high-temperature forms are considered in relation to the fluorite structure and mechanisms for the ionic conduction of these phases are proposed. A single crystal X-ray diffraction study of β-Ag2SO4 (25°C) reveals that it is isostructural with thenardite, V-Na 2SO4.The high-temperature modifications a-Ag2SO4 (490°C) and α-K2SO4 (620°C) have been characterised using PND data. A PND experiment on silver (I) fluoride confirms that it adopts the rocksalt structure and we find no firm evidence for a significant population of defects.</p

Liquid exfoliation of alkyl-ether functionalised layered metal-organic frameworks to nanosheets.

We report the synthesis of a 2D-layered metal-organic framework incorporating weakly interacting chains designed to aid exfoliation of the layers into nanosheets. Dispersion of the nanosheets exposes labile metal-sites which are shown to exchange solvent molecules allowing the nanosheets to act as sensors in suspension

Neutron diffraction study of the magnetic structures of manganese succinate Mn(C4H4O4): A complex inorganic-organic framework

The antiferromagnetic structures of the Mn succinate framework, Mn(C 4H4O4), have been determined using neutron diffraction. The structure comprises alternating layers containing chains of edge-sharing Mn (II) O6 octahedra and sheets of corner-sharing Mn (II) O6 octahedra, respectively, with a layer separation of �7.5. At 10 K the edge-sharing MnO6 octahedral chains order antiferromagnetically into a collinear sinusoidal spin structure with a propagation vector k2 = (0,-0.5225,0), in which individual edge-sharing MnO6 chains are ferromagnetically ordered. The sheets of corner-sharing MnO6 octahedra order magnetically at 6 K, adopting the antiferromagnetic structure expected for a square arrangement of cations with a propagation vector k8 = (-1,0,1). The ordering of these sheets at a lower temperature than the chains is consistent with their longer nearest-neighbor superexchange pathway. The magnetic structure of the edge-sharing layers is unaffected by the 6 K phase transition, indicating that the orderings of the two different layers are essentially independent of each other. © 2010 The American Physical Society

Preface to Special Topic: Metal-organic framework materials

10.1063/1.4902815APL Materials21212380

An extended Tolerance Factor approach for organic-inorganic perovskites

10.1039/c5sc00961hChemical Science663430-343

Structure-property correlations in Eu-doped tetra calcium phosphate phosphor: A key to solid-state lighting application

The unique emission characteristics and the crystal structure of Ca4(PO4)2O:Eu2+ were studied. Considerably broad emission from 500 nm to 800 nm was measured at 77 K when the material was excited at 365 nm. Its crystal structure was refined using neutron diffraction, allowing precise and accurate oxygen positions to be determined. This enabled a relationship between the optical properties and the crystal structure crucial for achieving a large redshift of the 5d level of Eu2+ to be established, which is important to match the excitation energy band with near-ultraviolet or blue light-emitting-diodes used for solid-state lighting. The importance of the anion polarizability and the distortion of the coordination polyhedron were also discussed