Ground state structural anomalies in cuprous halides: CuCl.

Abstract

We have examined structural instabilities and elastic anomalies in CuCl via first-principles calculations and find that its crystal structure is not ideal zinc blende but that correlated displacements of groups of four Cu atoms lead to a more stable configuration. About 20% of the Cu atoms are estimated to be affected. The Cu-Cu distance in the C${\mathrm{u}}_{4}$ complex shrinks from 3.82 to 2.72 \AA{}, close to that of metallic Cu. The energetics of defect formation are examined also for CuBr and CuI.