Local structural mechanisms (bond disorder, bond stiffness, short-range order) governing structural transitions and phonon scattering in qua

This research proposal aims to understand how local atomic disorder and soft chemical bonds control phase transitions and thermal conductivity in sulvanite materials. A multi-edge EXAFS/XANES study will directly probe the local structure—measuring bond lengths, force constants, and short-range order—in two related systems: Cu₄TiSe₄₋ₓSₓ and Ag₁₋ₓCu₃₊ₓTiSe₄. The goal is to determine how specific atomic substitutions (Se/S, Ag/Cu) and temperature induce disorder and "rattling," leading to structural phase changes and ultralow thermal conductivity. This element-resolved analysis will establish design principles for creating next-generation thermoelectric materials with tailored heat transport properties.