Vanadium trimers randomly aligned along the c-axis direction in layered LiVO 2

Herein, we discuss the identification of vanadium trimers in layered ${\mathrm{LiVO}}_{2}$ and its sulfide analog of ${\mathrm{LiVS}}_{2}$ with two-dimensional triangular lattices. Our comprehensive structural studies using synchrotron x-ray-diffraction experiments clarified that vanadium trimers are randomly aligned along the $c$-axis direction in ${\mathrm{LiVO}}_{2}$, while the long-range ordering of vanadium trimers along the $c$-axis direction appears in ${\mathrm{LiVS}}_{2}$. Our results solve the long-standing issue of cluster patterns in ${\mathrm{LiVO}}_{2}$ and provide an experimental basis for identifying the mechanism of trimer formation.