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

By use of synchrotron radiation the powder x-ray diffraction of LnSb (Ln=lanthanide) 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 (Ln=La, Ce, Pr, and Nd) have the tetragonal structure (distorted CsCl-type) at high pressures. The high-pressure form of the middle LnSb (Ln=Sm, Gd, and Th) is unknown. The heavier LnSb (Ln Dy, Ho, Er, Tm, and Lu) show the typical NaCl-CsCl (B1-B2) 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.