Infrared absorption in MgO microcrystals

Abstract

The dependence of the infrared-absorption properties on size variation and surface relaxation of rectangular MgO microcrystals (clusters) has been studied in the context of the rigid-ion model. The frequency ${\omega }_m$ of maximum absorption (for a given polarization direction) increases slightly with increase in cluster size from 180 to 900 ions, and also when surface relaxation of the cluster is taken into account. In all cases studied, ${\omega }_m$ is extremely close to the Fröhlich frequency ${\omega }_F$ for spherical particles treated in continuum theory. The total absorption is independent of crystal orientation and relaxation, and proportional to the number of particles in the cluster.