The lattice strains in a specimen (hexagonal system) compressed nonhydrostatically in an opposed anvil high pressure setup

A general expression has been derived for the lattice strain which corresponds to the measurement by x-ray diffraction method on a specimen (hexagonal system) compressed nonhydrostatically in an opposed anvil high pressure setup. The expressions relevant to the different diffraction geometries used in high pressure experiments with opposed anvils emerge as the special cases of this equation. The effect of the deviatoric stress component on the lattice parameters derived from the interplanar spacings measured at high pressure is discussed.