A new metastable phase of silicon in the \textit{Ibam} structure

ORAL

Abstract

In a study aimed at finding new useful forms of silicon, we use an \textit{ab initio} random structure searching (AIRSS) method to identify a new phase of silicon in the \textit{Ibam} structure. The \textit{Ibam} phase is found to be semimetallic within density functional theory with a small band overlap, and it is expected that quasiparticle corrections using the GW approximation would yield a semiconducting state with a small band gap. Calculation of the lattice dynamics reveals that the structure is locally stable. Enthalpy-pressure relations are calculated for the \textit{Ibam} structure as well as all other known Si structures, including the previously predicted phases st12 and bct. These results indicate that \textit{Ibam} silicon is metastable over the pressure range considered. Calculated coexistence pressures of the other known phase transitions are in good agreement with experimental observation.

–

Authors

  • Brad Malone

    Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Lab

  • Marvin Cohen

    Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, University of California at Berkeley and Lawrence Berkeley National Lab