First principles linear response calculations of lattice dynamics for CuCl

CuCl is known to exhibit large anharmonic effects and possibly a complicated multiwell Born-Oppenheimer surface reminiscent of the instabilities in perovskite ferroelectrics and cuprate superconductors. However, we have determined its phonon dispersion from first principles calculations and find it to agree well with low temperature experimental results. The calculations were carried out using a linear response formalism based on the linearized augmented plane wave method within the local density approximation. The calculated Born effective charges are within 10% of experiment and the high frequency dielectric constant ${\mathrm{\epsilon }}_{\mathrm{\infty }}$ is about 30% larger than the experimental value. This level of agreement is comparable to that attained in simpler semiconductors.