Linear compressibility quadric of hexagonal silver iodide

Abstract

The linear compressibilities of hexagonal silver iodide have been measured for eight different crystallographic directions. Samples inside a supported beryllium cylinder were subjected to hydrostatic pressure, and X-ray diffraction patterns were observed. Pressures within the vessel were determined by prior calibration against the known elastic constants of potassium iodide. The elliptic compressibility quadric was fitted by least squares to the linear compressibility data, yielding βα = 1.46 ± 0.42 × 10−6/bar and βc = 1.09 ± 0.32 × 10−6/bar. The large uncertainties attached to these values result from both the linear regression fits about the initial compression data (maximum of ±17%) and least-squares fit of the quadric surface (maximum of ±30%) to the linear compressibilities.