0000000000124232
AUTHOR
Eduardo Machado-charry
High-pressure electronic structure and phase transitions in monoclinic InSe: X-ray diffraction, Raman spectroscopy, and density functional theory
We have studied the crystal and electronic structure of monoclinic (MC) InSe under pressure finding a reversible phase transition to a ${\mathrm{Hg}}_{2}{\mathrm{Cl}}_{2}$-like tetragonal phase. The pressure evolution of the crystal structure was investigated by angle-dispersive x-ray diffraction and Raman spectroscopy in a diamond-anvil cell up to $30\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. From the diffraction experiments, we deduced that MC InSe becomes gradually more symmetric under pressure, transforming the crystal structure into a tetragonal one at $19.4\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. This phase transition occurs without any volume change. Ra…
GaS and InSe equations of state from single crystal diffraction
We have performed single crystal angle dispersive X-ray diffraction at high pressure in order to investigate the GaS and InSe equations of state. We situate the transition from β-GaS to GaS-II at 2 7 0 3. ± . GPa. In the InSe experiment we locate the beginning of the phase transition at 7.6 ± 0.6 GPa. The equations of state of β-GaS ( 0 43 27 0 06V = . ± . Å 3 , 37 2 GPaB = ± , 5 2B = .¢ ), GaS-II ( 0 42 4 0 2V = . ± . Å 3 , 50 3 GPaB = ± and 4 3 0 3B = . ± .¢ ) and γ-InSe ( 0 58 4 0 2V = . ± . Å 3 , 24 3 GPaB = ± and 8 6 0 8B = . ± .¢ ) are discussed and compared with the results of an ab-initio calculation.
First-principles study of the electronic structure of cubicGaS: Metallic versus insulating polymorphs
The electronic structure of different polymorphs of gallium sulphide $(\mathrm{GaS})$ with cubic structure is investigated by means of first-principles band structure calculations in connection with experimental reports on a metastable semiconducting cubic form of this material. The expected metallic character of simple cubic phases containing one $\mathrm{GaS}$ group per unit cell (rocksalt or zinc-blende) is confirmed by the calculations. A cubane-based zinc-blende structure is found to exhibit a band gap which is compatible with experimental results but the unit cell parameter is much larger than the reported ones. We have also studied cubic phases containing hydrogen. It is found that t…