The wurtzite to rock salt transition in CdSe: A comparison between molecular dynamics and metadynamics simulations

We compare the wurtzite (WZ) -> rock salt (RS) transition mechanisms seen in a molecular dynamics simulation at elevated pressure and in a metadynamics simulation close to the experimental transition pressure. The mechanism seen in the molecular dynamics is characterized by a direct compression parallel to the [10 (1) over bar0](WZ) direction, while in the metadynamics it is seen as a sliding of (1 (1) over bar 00)(WZ) layers parallel to the [0010](WZ) direction. The h-MgO structure is seen as an intermediate in both cases, although it is only stable at the lower pressure. The RS structure produced by the direct compression and that which results from the sliding-layer mechanism make an angle of 15 degrees with each other. Our metadynamics simulations along with other results suggest that sliding-layer mechanisms govern the transition close to the experimental transition pressure. (C) 2009 Elsevier Masson SAS. All rights reserved.