Investigation of Structural and Vibrational Properties of Topological Nodal‐Line Semimetal PtSn ₄ under Pressure

This work investigates the influence of external pressure on the structural and vibrational properties of the topological nodal line semimetal (TNLS), PtSn 4 , respectively, through synchrotron X‐ray diffraction and Raman spectroscopy. Systematic synchrotron high‐pressure (HP) diffraction data reveal that the ambient pressure orthorhombic crystal structure (space group Ccca) of PtSn 4 is stable at least until ≈24 GPa. However, the pressure dependence of the unit‐cell parameters is found to fall in different regimes: a low‐pressure regime with the bulk modulus ( B 0 ) of ≈83 up to ≈7.8 GPa and a pressure regime above with a significant increase in bulk modulus, B 0 of ≈235 GPa. This HP‐induced isostructural transition ≈7.8 GPa originates from the anisotropic compression of the in‐plane and out‐of‐plane axes of the orthorhombic lattice. HP Raman spectroscopy also shows the isostructural transition ≈7.8 GPa, coinciding with a distinct change in the pressure dependence of the Raman modes. Implications of the observed pressure‐induced isostructural transition on the TNLS nature of the PtSn 4 are going to be exciting to investigate through further experimental and theoretical tools.