Pseudo-one-dimensional ribbon chain cluster realized under high pressure in 1T−VSe2

We present a high-pressure single-crystal x-ray structure analysis of two-dimensional layered 1T-VSe₂, which is known to undergo an incommensurate charge density wave transition at 110 K at ambient pressure. When pressure is applied to 1T-VSe₂ at 150 K, a structural phase transition appears at about 8 GPa. The structural analysis of x-ray diffraction data obtained from a single crystal sample, with the correct corrections for the use of a diamond anvil cell and taking into account the effects of multiple domains, using only the superlattice peaks, reveals the appearance of ``ribbon chain'' type vanadium clusters at a high-pressure region. The formation of Se-Se bonds under high pressure and the associated unexpected charge injection into vanadium are largely responsible for the formation of ribbon-chain clusters. We discuss the possibility that such interanion bond formation occurs universally in the high-pressure phase of transition metal diserenides.