Pressure-induced structural and semiconductor-semiconductor transitions in Co0.5Mg0.5Cr2O4
The effect of pressure on the structural, vibrational, and electronic properties of Mg-doped Cr bearing spinel $\mathrm{C}{\mathrm{o}}_{0.5}\mathrm{M}{\mathrm{g}}_{0.5}\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{4}$ was studied up to 55 GPa at room-temperature using x-ray diffraction, Raman spectroscopy, electrical transport measurements, and ab initio calculations. We found that the ambient-pressure phase is cubic (spinel-type, $Fd\overline{3}m$) and underwent a pressure-induced structural transition to a tetragonal phase (space group $I\overline{4}m2$) above 28 GPa. The ab initio calculation confirmed this first-order phase transition. The resistivity of the sample decreased at low pressures …
Unprecedented pressure-driven metallization and topological charge transport in an anion radical salt
Abstract The hybrid inorganic/organic closed π -stacking and soft lattice of a copper anion radial (Copper-7,7,8,8-tetracyanoquinodimethane) renders its electrical conductivity and structural modifications, which are susceptible to temperature and pressure. The geometry of its metal-ligand construction contemplates the concept of topology with a charge-transfer instability. A pressure-induced ionic-neutral phase transition occurs and accompanies an anomalously large electrical conductivity, carries topological charges, and possesses a low energy gap smaller than the Coulomb gap. X-ray absorption spectroscopy of the metal establishes the high electrical conduction by the topological charges.…