Competing Electron-Deficient σ-Bond Configurations across Successive Structural Transitions in Li0.5VS2

Abstract

Unconventional bonding motifs, such as multicenter or electron-deficient σ bonds, have long been expected to provide a platform for unconventional electronic behavior, yet in many cases lead to electronically conventional ground states. Here, we investigate the layered vanadium chalcogenide Li0.5VS2, which exhibits successive structural and electronic transitions upon cooling. Using synchrotron X-ray and neutron diffraction measurements combined with theoretical calculations, we show that the system undergoes a reorganization of bonding configurations from zigzag-chain networks in the intermediate-temperature phase to more localized dimer-like states at low temperatures. These distinct bonding configurations are accompanied by a crossover from Curie–Weiss-like magnetism to a nonmagnetic state, while retaining metallic conductivity. Our results indicate that electron-deficient bonding can act as an emergent electronic degree of freedom that reorganizes in response to external conditions. More broadly, this work provides a conceptual framework for understanding how bonding configurations mediate competing electronic states in correlated materials.