71 research outputs found
Superconductivity in Te-deficient ZrTe
We present structural, electrical, and thermoelectric potential measurements
on high-quality single crystals of ZrTe grown from isothermal chemical
vapor transport. These measurements show that the Te-deficient ZrTe,
which forms the same structure as the non-superconducting ZrTe, is
superconducting below 3.2\,K. The temperature dependence of the upper critical
field (H) deviates from the behavior expected in conventional
single-band superconductors, being best described by an electron-phonon two-gap
superconducting model with strong intraband coupling. For the ZrTe
single crystals, the Seebeck potential measurements suggest that the charge
carriers are predominantly negative, in agreement with the ab initio
calculations. Through first-principles calculations within DFT, we show that
the slight reduction of Te occupancy in ZrTe unexpectedly gives origin to
density of states peaks at the Fermi level due to the formation of localized
Zr- bands, possibly promoting electronic instabilities at the Fermi level
and an increase at the critical temperature according to the standard BCS
theory. These findings highlight that the Te deficiency promotes the electronic
conditions for the stability of the superconducting ground state, suggesting
that defects can fine-tune the electronic structure to support
superconductivity
Assessment techniques, database design and software facilities for thermodynamics and diffusion
The purpose of this article is to give a set of recommendations to producers of assessed thermodynamic data, who may be involved in either the critical evaluation of limited chemical systems or the creation and dissemination of larger thermodynamic databases. Also, it is hoped that reviewers and editors of scientific publications in this field will find some of the information useful. Good practice in the assessment process is essential, particularly as datasets from many different sources may be combined together into a single database. With this in mind, we highlight some problems that can arise during the assessment process and we propose a quality assurance procedure. It is worth mentioning at this point, that the provision of reliable assessed thermodynamic data relies heavily on the availability of high quality experimental information. The different software packages for thermodynamics and diffusion are described here only briefly
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