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The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra.(More)
The MgxZn(1-x)O alloy system may provide an optically tunable family of wide band gap materials that can be used in various UV luminescences, absorption, lighting, and display applications. A systematic investigation of the MgO-ZnO system using ab initio evolutionary simulations shows that MgxZn(1-x)O alloys exist in ordered ground-state structures at(More)
The crystal structures and properties of hafnium hydride under pressure are explored using the first-principles calculations based on density function theory. The material undergoes pressure-induced structural phase transition I4/mmm → Cmma → P21/m at 180 and 250 GPa, respectively, and all of these structures are metallic. The superconducting critical(More)
We report angle dispersive X-ray diffraction (XRD) measurements and Raman spectroscopy on NH4Br up to 70.0 GPa at room temperature. Three thermodynamically stable phases (phases II, IV, and V) are confirmed and a new possible phase (phase VI) of P21/m symmetry is proposed whose structure was established from Rietveld refinement of synchrotron XRD data for(More)
The high-pressure behaviors of nitrogen-rich 1H-tetrazole (CH2N4) have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman scattering up to 75 GPa. A first crystalline-to-crystalline phase transition is observed and identified above ~3 GPa with a large volume collapse (∼18% at 4.4 GPa) from phase I to phase II. The new phase II forms(More)
Motivated by the potential high temperature superconductivity in hydrogen-rich materials, high-pressure structures of ErH3 and HoH3 were studied by using genetic algorithm method. Our calculations indicate that both ErH3 and HoH3 transform from P-3c1 structure to a monoclinic C2/m structure at about 15 GPa, and then transforms into a cubic Fm-3m structure(More)
A detailed high-pressure study on NH3BH3 has been carried out using in situ synchrotron X-ray diffraction (XRD) and Raman scattering with a diamond anvil cell up to 20 and 33 GPa, respectively. The Rietveld refinement based on the XRD pattern and analysis of Raman data indicate two first-order phase transitions from the ambient pressure I4 mm structure(More)
Niobium-nitrogen compounds, which are potential candidates for superhard multifunctional materials, may possess multiple stoichiometries and structures under pressure. Based on ab initio evolutionary structural searches, we predict three ground states (oP6-Nb2N, CW-NbN, and hP22-Nb5N6) and six stable high pressure phases (ε-NbN, AsNi-NbN, U2S3-Nb2N3,(More)