| The pressure-induced phase structure transition behaviors inⅢ-Ⅴbinary compounds are very rich, for mostⅢ-Ⅴbinary compounds consist of light mass element, they are semiconductors at ambient pressure and crystallize in ZB structure, at ultra-high pressure, the B2 phase has been considered to be a candidate structure. But for InBi, which isⅢ-Ⅴbinary compound consist of heavy mass element, forms a semimetallic compound with simple tetragonal P4/nmm structure. Until now, high pressure experiment up to 75 GPa of InBi reveals two phase transitions, from tetragonal B10 structure (P4/nmm) , via a isostructural phase transition, to another tetragonalβ-Np structure (P4/nmm), then to a site-disordered tetragonal structure, but on decompression from 75 GPa, hints for the possible stability of a new site-disordered cubic structure. So, is the suspected cubic phase the really fourth phase ? which structures will InBi crystallize in at higher pressure ? therefore, studying the high pressure phase transition sequence of InBi can not only contribute to the understanding of the mechanism of the structure bahaviors of theⅢ-Ⅴbinary compounds under pressure, but also contribute to the studying the high pressure phase transition of otherⅢ-ⅤandⅡ-Ⅵbinary compounds.Ab initio calculations within the framework of density-functional theory has been employed in this theis to study the pressure-induced phase transition of InBi, and we get some interesting results :(1) In metal and related-compounds, isostructure phase transition at high pressure is almost induced by ETT, InBi is semi-metal at ambient pressure, and the to a metallic phase through a isostructure transition at pressure, so, is this isostructure phase transition induced by ETT ? from analyzing the band structures of the first and second phase, we find that the conducting bands along A→Z andг→Z directions which do not cross the fermi surface in the first phase have already crossed the fermi surface in the second phase, the conducting bands at R point which cross the fermi surface not clearly have crossed the fermi surface clearly in the second phase, these phenomenons clearly demonstrate that an ETT has occured at high pressure, the phase transition pressure from first phase to second phase is 12.4 GPa from the enthalpy calculations, which is in accordance with the pressure of ETT between 8 to 14 GPa, so, the ETT of the first phase under pressure is the physical mechanism for the isostructural phase transiton in InBi.(2) The evolutionary methodology is employed to predicted the high-pressure crystallography of InBi, an orthorhombic Imma structure is predicted to be the fourth high pressure structure at first time, ehthalpy calculation demonstrates that, our predicted orthorhombic structure is energetic lower than the suspected cubic phase from experiment, the EOS from theoretical modification is greatly accordance with the experimental results, especially in the pressure range of our predicted fourth phase , ADXD modeling of suspected cubic phase and our predicted orthorhombic phase gets very similar results, these demonstrate that our predicted orthorhombic phase is the more reasonable structure candidate than the cubic phase suspected from the experiment.(3) We firstly predicted that the fifth phase crystrallize the tetragonal P4/nmm phase, this phase has the same space group with the ambient pressure phase, but from the different lattice constanes ratio and different atom occupying style, they are two different structure, the coordination number of this phase is"8+4", which demonstrates a very dense structure. interesting , we predicted the same tetragonal P4/nmm phase in ZnTe, and the pressure range of this predicted phase ouucring is greatly accordance with the experimental results, so we suspect that our predicted tetragonal P4/nmm phase is a common high pressure phase of heavierⅢ-ⅤandⅡ-Ⅵcompounds , which is expected to be vertified by high pressure experiments.
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