867 research outputs found
Potential ring of Dirac nodes in a new polymorph of CaP
We report the crystal structure of a new polymorph of CaP, and an
analysis of its electronic structure. The crystal structure was determined
through Rietveld refinements of powder synchrotron x-ray diffraction data.
CaP is found to be a variant of the MnSi structure type, with a
Ca ion deficiency compared to the ideal 5:3 stoichiometry to yield a
charge-balanced compound. We also report the observation of a secondary phase,
CaPH, in which the Ca and P sites are fully occupied and the presence
of interstitial hydride ions creates a closed-shell electron-precise compound.
We show via electronic structure calculations of CaP that the compound
is stabilized by a gap in the density of states compared to the hypothetical
compound CaP. Moreover, the calculated band structure of CaP
indicates that it should be a three-dimensional Dirac semimetal with a highly
unusual ring of Dirac nodes at the Fermi level. The Dirac states are protected
against gap opening by a mirror plane in a manner analogous to graphene. The
results suggest that further study of the electronic properties of CaP
will be of interest
Dimeric benzoboroxoles for targeted activity against Mycobacterium tuberculosis
Dimeric benzoboroxoles that are covalently linked by a short scaffold enhance selective anti-tubercular activity. These multimeric benzoboroxole compounds are capable of engaging the specific extracellular Mycobacterium tuberculosis glycans, do not lead to the evolution of resistance and bypass the need to cross the impermeable mycobacterial cell envelope barrier
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