Huadi Zhang | Searcharxiv

arXiv2016

Crossover from Metal to Insulator in Dense Lithium-Rich Compound $\textrm{CLi}_{4}$

Crystal structures of $\textrm{CLi}_4$ compounds are explored through \emph{ab} \emph{initio} evolutionary methodology. Phase transition from metal to semimetal and semiconductor, and eventually to insulator with increasing pressure are revealed under pressure. Pressure-induced evolution of anti-metallization has been described quantitatively by Fermi Surface Filling Ratio and electron energy band gap using \emph{ab} \emph{initio} \emph{GW} calculations. Anti-metallization is attributed to the hybrid valence electrons and their repulsion by core electrons into the lattice interstices. Very weak electron-phonon coupling interactions are found in the metallic phases, resulting in very low superconducting temperature.

cond-mat.mtrl-sci↗

arXiv2015

Phase diagram and superconductivity of polonium hydrides under high pressure

High pressure structures, phase diagram and superconductivity of polonium hydrides have been systematically investigated through the first-principles calculations based on the density functional theory. With the increasing pressure, several stoichiometries (PoH, $\textrm{PoH}_\textrm{2}$, $\textrm{PoH}_4$ and $\textrm{PoH}_6$) are predicted to stabilize in the excess hydrogen environment. All of the reported hydrides, exception of PoH, exhibit intriguing structural character with the appearing $\textrm{H}_2$ units. Moreover, our electronic band structure and the projected density of states (PDOS) demonstrate that these energetically stable phases are metallic. The application of the Allen-Dynes modified McMillan equation with the calculated electron-phonon coupling parameter reveals that $\textrm{PoH}_4$ is a superconductor with a critical temperature $T_c$ of 41.2-47.2 K at 300 GPa.

cond-mat.supr-con↗