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The high pressure structural properties of bismuth oxide Bi2SiO5 have been investigated up to 28 GPa using in situ powder synchrotron X-ray diffraction and up to 50 GPa with DFT calculations. The monoclinic structure is found to persist up to about 20 GPa, where a notable change in the compressibility occurs. The DFT data imply that this is due to a second-order phase transition from the ambient condition monoclinic structure with space group Cc to an orthorhombic polymorph with space group Cmcm. This transition involves the straightening of the chains formed by corner-connected SiO4 tetrahedra, that suppresses the ferroelectricity in the high pressure, centrosymmetric phase of Bi2SiO5. The stereo-chemical activity of the Bi3+ lone electron pair is found to decrease with increasing pressure, but it can still be identifed in the calculated electron density difference maps at 50 GPa.
GaTa$_4$Se$_8$ belongs to the lacunar spinel family. Its crystal structures is still a puzzle though there have been intensive studies on its novel properties, such as the Mott insulator phase and superconductivity under pressure. In this work, we in
We study the possibility of pressure-induced transitions from a normal semiconductor to a topological insulator (TI) in bismuth tellurohalides using density functional theory and tight-binding method. In BiTeI this transition is realized through the
The elastic, thermodynamic, and electronic properties of fluorite RuO_2 under high pressure are investigated by plane-wave pseudopotential density functional theory. The optimized lattice parameters, elastic constants, bulk modulus, and shear modulus
Based on the first-principles calculations, we have investigated the geometry, binding properties, density of states and band structures of the novel superconductor LaFe1-xCoxAsO and its parent compounds with the ZrCuSiAs structure. We demonstrate th
We present results of electronic band structure, Fermi surface and electron transport properties calculations in orthorhombic $n$- and $p$-type SnSe, applying Korringa-Kohn-Rostoker method and Boltzmann transport approach. The analysis accounted for