Internal strain and dynamic effective charges in CuCl and CuBr

Abstract

Self-consistent local-density theory has been used in the embedded-molecular-cluster framework to study the internal strain and response of the electronic charge distribution to external fields in CuCl and CuBr. The piezoelectric response and dynamic effective charges have been determined following the formalism developed by Martin. We find that rather small clusters are able to reproduce energy-level features deduced from experiment and band-structure models. The bulk lattice constant is reproduced to within 4% and calculated deformation properties show that the Cu--halogen bond is relatively rigid.