Session P25: Focus Session: Simulation of Matter at Extreme Conditions - Static Pressure

8:00 AM–11:00 AM, Wednesday, February 29, 2012
Room: 257A

Sponsoring Units: DCOMP GSCCM DMP
Chair: Ronald Cohen, Carnegie Institution of Washington

Abstract ID: BAPS.2012.MAR.P25.1

Abstract: P25.00001 : A new metastable phase of silicon in the \textit{Ibam} structure

8:00 AM–8:12 AM

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Authors:

  Brad D. Malone
    (Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory)

  Marvin L. Cohen
    (Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory)

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.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.P25.1