Lattice dynamics ofRb71K29: Molecular dynamics study

Interionic potentials have been constructed to describe the lattice dynamics of the alloy ${\mathrm{Rb}}_{71}$ ${\mathrm{K}}_{29}$. Using these, computer-simulation molecular-dynamics calculations have been carried out for a system of 432 particles, periodic boundary conditions being used to approximate the infinite system. The results show that considerable local structural relaxation occurs around the K atoms. The dynamical structure factor $S(\overrightarrow{\mathrm{Q}}, \omega )$ has been calculated for selected wave vectors corresponding closely to those studied experimentally by Kamitakahara and Copley. There is excellent agreement with the experimental data where comparison is possible, both with respect to the local modes and to the host lattice frequencies.