Differing pressure response of lattice structure in LaTMSb2 (TM = Au or Ag) ternary antimonides

Ternary antimonides LaTMSb2 (TM = Au or Ag) share identical lattice symmetry and exhibit the charge density wave (CDW) phenomenon. The CDW is found to be tunable either by physical or chemical pressure, triggering the investigation of the pressure response of these systems. Here, we compare the lattice structure response of the two systems to the hydrostatic pressure. Under hydrostatic pressure, the lattice structure of LaAgSb2 transformed from tetragonal to a mixed tetragonal (>4 GPa) followed by monoclinic (4–9 GPa) and then to a mixed monoclinic and orthorhombic (9–41.8 GPa) phases. In contrast, our synchrotron X-ray diffraction results on LaAuSb2 reveal that the tetragonal structure is stable in the pressure range of 0–12.2 GPa. Our experimental investigation is well supported by the density functional theory (DFT) calculations. We have used DFT to identify the experimental Raman vibrational modes at ambient conditions. We highlight the importance of structural subtleties in the differing pressure response of the ternary antimonides.