74 research outputs found
Investigation of seepage around the bucket skirt during installation in sand:AAU CPT-based method for the installation of suction bucket
Unexpected coexisting solid solutions in the quasi-binary Ag(II)F2/Cu(II)F2 phase diagram
High-temperature solid-state reaction between orthorhombic AgF2 and
monoclinic CuF2 (y = 0.15, 0.3, 0.4, 0.5) in a fluorine atmosphere resulted in
coexisting solid solutions of Cu-poor orthorhombic and Cu-rich monoclinic
phases with stoichiometry Ag1-xCuxF2. Based on X-ray powder diffraction
analyses, the mutual solubility in the orthorhombic phase (AgF2 doped with Cu)
appears to be at an upper limit of Cu concentration of 30 mol % (Ag0.7Cu0.3F2),
while the monoclinic phase (CuF2 doped with Ag) can form a nearly
stoichiometric Cu : Ag = 1 : 1 solid solution (Cu0.56Ag0.44F2), preserving the
CuF2 crystal structure. Experimental data and DFT calculations showed that AgF2
doped with Cu and CuF2 doped with Ag solid solutions deviate from the classical
Vegards law. Magnetic measurements of Ag1-xCuxF2 showed that the Neel
temperature (TN) decreases with increasing Cu content in both phases. Likewise,
theoretical DFT+U calculations for Ag1-xCuxF2 showed that the progressive
substitution of Ag by Cu decreases the magnetic interaction strength (J2D) in
both structures. Electrical conductivity measurements of Ag0.85Cu0.15F2 showed
a ca. 2-fold increase in specific ionic conductivity (3.71 x 10-13 plus/minus
2.6 x 10-15 S/cm) as compared to pure AgF2 (1.85 x 10-13 plus/minus 1.2 x 10-15
S/cm), indicating the formation of a vacancy- or F adatom-free metal difluoride
sample.Comment: 9 pages, 4 figures, 1 Table, and electronic supplement of 14 page
Low temperature magnetism of KAgF3
KAgF is a quasi one-dimensional quantum antiferromagnet hosting a series
of intriguing structural and magnetic transitions. Here we use powder neutron
diffraction, SR spectroscopy, and Density Functional Theory calculations
to elucidate the low temperature magnetic phases. Below K we find
that the material orders as an A-type antiferromagnet with an ordered moment of
0.47. Both neutrons and muons provide evidence for an intermediate
phase at temperatures with K from a
previous magnetometry study. However, the evidence is at the limit of detection
and its nature remains an open problem.Comment: 11 pages, 8 figures. Supplementary information is included in a
separate fil
Charge Transfer and excitations in AgF
Charge transfer (CT) insulators are the parent phase of a large group of
today's unconventional high temperature superconductors. Here we study
experimentally and theoretically the interband excitations of the CT insulator
silver fluoride AgF, which has been proposed as an excellent analogue of
oxocuprates. Optical conductivity and resonant inelastic x-ray scattering
(RIXS) on AgF polycrystalline sample show a close similarity with that
measured on undoped LaCuO. While the former shows a CT gap
3.4~eV, larger than in the cuprate, -excitations are nearly at the
same energy in the two materials. DFT and exact diagonalization cluster
computations of the multiplet spectra show that AgF is more covalent than
the cuprate, in spite of the larger fundamental gap. Furthermore, we show that
AgF is at the verge of a charge transfer instability. The overall
resemblance of our data on AgF to those published previously on
LaCuO suggests that the underlying CT insulator physics is the same,
while AgF could also benefit from a proximity to a charge density wave
phase as in BaBiO. Therefore, our work provides a compelling support to the
future use of fluoroargentates for materials' engineering of novel
high-temperature superconductors.Comment: 13 pages, 9 Figures (including SI
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An analysis of a joint shear model for jointed media with orthogonal joint sets; Yucca Mountain Site Characterization Project
This report describes a joint shear model used in conjunction with a computational model for jointed media with orthogonal joint sets. The joint shear model allows nonlinear behavior for both joint sets. Because nonlinear behavior is allowed for both joint sets, a great many cases must be considered to fully describe the joint shear behavior of the jointed medium. An extensive set of equations is required to describe the joint shear stress and slip displacements that can occur for all the various cases. This report examines possible methods for simplifying this set of equations so that the model can be implemented efficiently form a computational standpoint. The shear model must be examined carefully to obtain a computationally efficient implementation that does not lead to numerical problems. The application to fractures in rock is discussed. 5 refs., 4 figs
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