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Kagomé metals are widely recognized, versatile platforms for exploring topological properties, unconventional electronic correlations, magnetic frustration, and superconductivity. In theRV₆Sn₆family of materials (R= Sc, Y, Lu), ScV₆Sn₆hosts an unusual charge density wave ground state as well as structural similarities with theAV₃Sb₅system (A= K, Cs, Rb). In this work, we combine Raman scattering spectroscopy with first-principles lattice dynamics calculations to reveal phonon mixing processes in the charge density wave state of ScV₆Sn₆. In the low temperature phase, we find at least four new peaks in the vicinity of the V-containing totally symmetric mode near 240 cm⁻¹suggesting that the density wave acts to mix modes ofP6/mmmand$$R\bar{3}m$$$R\overline{3}m$symmetry - a result that we quantify by projecting phonons of the high symmetry state onto those of the lower symmetry structure. We also test the stability of the short-range ordered density wave state under compression and propose that both physical and chemical pressure quench the effect. We discuss these findings in terms of symmetry and the structure-property trends that can be unraveled in this system.

 

Using in situ atomic-resolution scanning transmission electron microscopy, atomic movements and rearrangements associated with diffusive solid to solid phase transformations in the Pt−Sn system are captured to reveal details of the underlying atomistic mechanisms that drive these transformations. In the PtSn4 to PtSn2 phase transformation, a periodic superlattice substructure and a unique intermediate structure precede the nucleation and growth of the PtSn2 phase. At the atomic level, all stages of the transformation are templated by the anisotropic crystal structure of the parent PtSn4 phase. In the case of the PtSn2 to Pt2Sn3 transformation, the anisotropy in the structure of product Pt2Sn3 dictates the path of transformation. Analysis of atomic configurations at the transformation front elucidates the diffusion pathways and lattice distortions required for these phase transformations. Comparison of multiple Pt−Sn phase transformations reveals the structural parameters governing solid to solid phase transformations in this technologically interesting intermetallic system.