49 research outputs found
Nature of the spin dynamics and 1/3 magnetization plateau in azurite
We present a specific heat and inelastic neutron scattering study in magnetic
fields up into the 1/3 magnetization plateau phase of the diamond chain
compound azurite Cu(CO)(OH). We establish that the
magnetization plateau is a dimer-monomer state, {\it i.e.}, consisting of a
chain of monomers, which are separated by dimers on the
diamond chain backbone. The effective spin couplings K
and K are derived from the monomer and dimer
dispersions. They are associated to microscopic couplings K,
K and a ferromagnetic K, possibly as
result of orbitals in the Cu-O bonds providing the superexchange
pathways.Comment: 5 pages, 4 figure
Ionic adsorption on the brucite (0001) surface:a periodic electrostatic embedded cluster method study
Density functional theory (DFT) at the generalised gradient approximation level is employed within the periodic electrostatic embedded cluster method (PEECM) to model the brucite (0001) surface. Three representative studies are then used to demonstrate the reliability of the PEECM for the description of the interactions of various ionic species with the layered Mg(OH)2 structure, and its performance is compared with periodic DFT, an approach known to be challenging for the adsorption of charged species. The adsorption energies of a series of s block cations, including Sr2+ and Cs+ which are known to coexist with brucite in nuclear waste storage ponds, are well described by the embedded cluster model, provided that basis sets of triple-zeta quality are employed for the adsorbates. The substitution energies of Ca2+ and Sr2+ into brucite obtained with the PEECM are very similar to periodic DFT results, and comparison of the approaches indicates that two brucite layers in the quantum mechanical part of the PEECM are sufficient to describe the substitution. Finally, a detailed comparison of the periodic and PEECM DFT approaches to the energetic and geometric properties of differently coordinated Sr[(OH)2(H2O)4] complexes on brucite shows an excellent agreement in adsorption energies, Sr–O distances, and bond critical point electron densities (obtained via the quantum theory of atoms-in-molecules), demonstrating that the PEECM can be a useful alternative to periodic DFT in these situations
Structure and elastic properties of Mg(OH) from density functional theory
The structure, lattice dynamics and mechanical properties of the magnesium
hydroxide have been investigated with static density functional theory
calculations as well as \it {ab initio} molecular dynamics. The hypothesis of a
superstructure existing in the lattice formed by the hydrogen atoms has been
tested. The elastic constants of the material have been calculated with static
deformations approach and are in fair agreement with the experimental data. The
hydrogen subsystem structure exhibits signs of disordered behaviour while
maintaining correlations between angular positions of neighbouring atoms. We
establish that the essential angular correlations between hydrogen positions
are maintained to the temperature of at least 150 K and show that they are well
described by a physically motivated probabilistic model. The rotational degree
of freedom appears to be decoupled from the lattice directions above 30K
Magnetic properties of the distorted diamond chain at T=0
We explore, at T=0, the magnetic properties of the antiferromagnetic
distorted diamond chain described by the Hamiltonian {\cal H}
= \sum_{j=1}^{N/3}{J_1 ({\bi S}_{3j-1} \cdot {\bi S}_{3j}
+ {\bi S}_{3j} \cdot {\bi S}_{3j+1})
+ J_2 {\bi S}_{3j+1} \cdot {\bi S}_{3j+2}
+ J_3 ({\bi S}_{3j-2} \cdot {\bi S}_{3j}
+ {\bi S}_{3j} \cdot {\bi S}_{3j+2})}
\allowbreak - H \sum_{l=1}^{N} S_l^z with , which well
models with , and azurite . We employ the physical
consideration, the degenerate perturbation theory, the level spectroscopy
analysis of the numerical diagonalization data obtained by the Lanczos method
and also the density matrix renormalization group (DMRG) method. We investigate
the mechanisms of the magnetization plateaux at and , and
also show the precise phase diagrams on the plane
concerning with these magnetization plateaux, where
and is the saturation magnetization. We also calculate the magnetization
curves and the magnetization phase diagrams by means of the DMRG method.Comment: 21 pages, 29 figure
Intangible Resources as Performance Drivers in European Hospitals.
Purpose – The purpose of this paper is to explore the use of intangible resources in the performance
management of European hospitals. The extent of the awareness of intangible resources as
performance drivers is examined in five different European hospitals, from both the private and the
public sector.
Design/methodology/approach – An inductive approach was taken based on open ended,
semi-structured interviews with key informants.
Findings – Research results indicate that hospitals’ managers realise the importance of intangible
resources. In particular these relate to three different areas, namely the management of hospitals’
human resources, the creation of relationships within and outside the organisation, and the
measurement of individual performance.
Research limitations/ implications – This research is exploratory in nature. Further and deeper
research is needed which focuses on the identification of the most relevant resources in hospitals and
their impact on performance. Both will then justify the integration of these intangible resources in
performance measurement systems.
Originality/value – This research gives insights into the awareness of intangible resources in
different European hospitals. It explores the use of intangible resources in performance measurement
systems. Much of the research in this area has been concentrated on the private commercial sector,
linked to creating shareholder value, and this paper adds to the newly developing research looking at
hospital settings