Investigating the local structure of TiSe2 with symmetry-informed pair distribution function analysis*

TiSe2 is an important member of the transition metal dichalcogenide family of materials known for their scientific and technological richness. TiSe2 undergoes a charge density wave (CDW) transition at 200 K, the origin of which has been hotly debated for over 40 years. Even the basic nature of the normal state and ground states as either semiconducting, semimetallic, or metallic is not entirely clear. This confusion stems in large part from the profound sample dependence of the electronic properties of TiSe2, obscuring the intrinsic material properties. To help clarify these issues, we have performed pair distribution function analysis of x-ray and neutron total scattering data collected from three different samples of TiSe2. Using symmetry mode amplitudes as the basis for structural refinements, we are able to probe the CDW transition and gain insight into the local atomic structure and its relation to the observed properties of TiSe2.