• High pressure structural stability of UO$_2$ by evolutionary algorithm

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    • Keywords


      UO$_2$; high pressure; evolutionary algorithm; bulk modulus; enthalpy; phase transition.

    • Abstract


      The aim of this study is to investigate the crystal structure stability of UO$_2$ upon applying pressure using an evolutionary algorithm. UO$_2$ exhibits face-centred cubic crystal structure with space group $Fm\bar{3}m$ (S.G. No. 225) in the ambient pressure, and above 82 GPa transforms to an orthorhombic structure with space group Pnma (S.G. No. 62). The first-order structural phase transition is accompanied by a 5.4% volume collapse. The lattice parameters of both the cubic and orthorhombic phases decrease with the applied pressure. The bulk modulus ($B_o$) and the pressure derivative of bulk modulus ($B'_{o}$) values of the cubic phase were found to be 210.41 ± 0.22 GPa and 3.60 ± 0.01, respectively. The $B_o$ and $B'_{o}$ values of the orthorhombic phase were found to be 218.09 ± 3.29 GPa and 3.64 ± 0.03, respectively. The enthalpy of formation linearly increases with the applied pressure for both the cubic and orthorhombic phases, and at 82 GPa theenthalpy of the orthorhombic phase is found to be lower than the cubic phase indicating the structural phase transition.

    • Author Affiliations



      1. High Pressure Studies Section, Condensed Matter Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
    • Dates

  • Bulletin of Materials Science | News

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