92 research outputs found
Total Cluster Energy Calculation of Lithium Ion Conductors by the DV-Xα Method
Recently several programs for the total cluster energy calculation have been developing in the DV-Xα method. In this study, we have tried to calculate and compare total cluster energies of several diatomic molecules and model clusters of ionic conductors. The total cluster energies of diatomic molecules have minimum near the equilibrium atomic distance of each molecules though the absolute value of the total cluster energy were slightly different each other. In the case of the model cluster of the Li3N crystal, which is one of the typical Li ion conductors, we have obtained the energy change as a function of the site during the movement of a Li ion. The energy change with the movement of the Li ion along the conduction path was considerably smaller than along other paths, consistent with the results by the band calculation and experiments. The total cluster energy calculation method was enough useful for the discussion of the cluster energy
Chemical bonding of Ag ions in AgI-based superionic conducting glasses
The electronic state of AgI-based superionic conducting glasses was calculated by the DV-Xα cluster method. We have adopted several model clusters with different conduction paths of Ag ions. The electronic state of the similar clusters using Na ions was also calculated for comparison. The net charge of moving cations and the total bond order between the moving cation and the other ions in these model clusters were used for discussion of chemical bonding of the moving cation. The total bond order of the moving Ag ion was decreased with the movement and had a minimum at the middle of the path. The variation of the total bond order of the Ag ion was much smaller than that of the Na ion in any conduction paths. On the other hand, the change of the net charge of the Ag ion with the movement was almost the same as that of the Na ion. These results suggest that the smaller change of the total bond order of the Ag ion should play an important role in the fast ion conduction in AgI-based superionic conducting glasses, rather than the change of the net charge of cations
Electronic structure of crystalline binary and ternary Cd-Te-O compounds
The electronic structure of crystalline CdTe, CdO, -TeO,
CdTeO and CdTeO is studied by means of first principles
calculations. The band structure, total and partial density of states, and
charge densities are presented. For -TeO and CdTeO, Density
Functional Theory within the Local Density Approximation (LDA) correctly
describes the insulating character of these compounds. In the first four
compounds, LDA underestimates the optical bandgap by roughly 1 eV. Based on
this trend, we predict an optical bandgap of 1.7 eV for CdTeO. This
material shows an isolated conduction band with a low effective mass, thus
explaining its semiconducting character observed recently. In all these oxides,
the top valence bands are formed mainly from the O 2p electrons. On the other
hand, the binding energy of the Cd 4d band, relative to the valence band
maximum, in the ternary compounds is smaller than in CdTe and CdO.Comment: 13 pages, 15 figures, 2 tables. Accepted in Phys Rev
Organic Superconductors: when correlations and magnetism walk in
This survey provides a brief account for the start of organic
superconductivity motivated by the quest for high Tc superconductors and its
development since the eighties'. Besides superconductivity found in 1D organics
in 1980, progresses in this field of research have contributed to better
understand the physics of low dimensional conductors highlighted by the wealth
of new remarkable properties. Correlations conspire to govern the low
temperature properties of the metallic phase. The contribution of
antiferromagnetic fluctuations to the interchain Cooper pairing proposed by the
theory is borne out by experimental investigations and supports
supercondutivity emerging from a non Fermi liquid background. Quasi one
dimensional organic superconductors can therefore be considered as simple
prototype systems for the more complex high Tc materials.Comment: 41 pages, 21 figures to be published in Journal of Superconductivity
and Novel Magnetis
A novel fluorescein-bisphosphonate based diagnostic tool for the detection of hydroxyapatite in both cell and tissue models
Abstract A rapid and efficient method for the detection of hydroxyapatite (HAP) has been developed which shows superiority to existing well-established methods. This fluorescein-bisphosphonate probe is highly selective for HAP over other calcium minerals and is capable of detecting lower levels of calcification in cellular models than either hydrochloric acid-based calcium leaching assays or the Alizarin S stain. The probe has been shown to be effective in both in vitro vascular calcification models and in vitro bone calcification models. Moreover we have demonstrated binding of this probe to vascular calcification in rat aorta and to areas of microcalcification, in human vascular tissue, beyond the resolution of computed tomography in human atherosclerotic plaques. Fluorescein-BP is therefore a highly sensitive and specific imaging probe for the detection of vascular calcification, with the potential to improve not only ex vivo assessments of HAP deposition but also the detection of vascular microcalcification in humans
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