1ST PRINCIPLES LINEAR-RESPONSE CALCULATIONS OF LATTICE-DYNAMICS FOR CUCL

CuCl is known to exhibit large anharmonic effects and possibly a compl icated multiwell Born-Oppenheimer surface reminiscent of the instabili ties in perovskite ferroelectrics and cuprate superconductors. However , we have determined its phonon dispersion from first principles calcu lations and find it to agree well with low temperature experimental re sults. The calculations were carried out using a linear response forma lism based on the linearized augmented plane wave method. Born effecti ve charges are within 10% of experiment and the dielectric constant ep silon(infinity) is about 30% larger than the experimental value. This level of agreement is comparable to that attained in simpler semicondu ctors.