Pressure-induced phase transitions in lanthanide monoantimonides with a NaCl-type structure

By use of synchrotron radiation the powder x-ray diffraction of LnSb $(\mathrm{L}\mathrm{n}=\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{h}\mathrm{a}\mathrm{n}\mathrm{i}\mathrm{d}\mathrm{e})$ with a NaCl-type structure has systematically been studied up to 40 GPa at room temperature. First-order phase transitions with the crystallographic change occur for LnSb at high pressures. The structure of the high-pressure phases of LnSb is classified into three groups. The lighter LnSb $(\mathrm{L}\mathrm{n}=\mathrm{L}\mathrm{a},$ Ce, Pr, and Nd) have the tetragonal structure (distorted CsCl-type) at high pressures. The high-pressure form of the middle LnSb $(\mathrm{L}\mathrm{n}=\mathrm{S}\mathrm{m},$ Gd, and Tb) is unknown. The heavier LnSb $(\mathrm{L}\mathrm{n}=\mathrm{D}\mathrm{y},$ Ho, Er, Tm, and Lu) show the typical NaCl-CsCl $\mathrm{}(B1-B2\mathrm{})\mathrm{}$ transition at high pressures though the same transition is not observed in the heavier LnP and LnAs. The transition pressures of LnSb increase with decreasing lattice constant in the NaCl-type structure and do not depend on the structure of their high-pressure phases. The high-pressure structural behavior of LnSb is discussed.