Quasi-stable structures in equilibrium dense bismuth melt: Experimental and first principles theoretical studies

Near the melting temperature, equilibrium bismuth melt is characterized by structural features that are absent in equilibrium monatomic simple liquids. In the present work, the structure of bismuth melt is studied by X-ray diffraction experiments and quantum chemical calculations. The presence of quasi-stable structures in the melt has been found, the lifetime of which exceeds the structural relaxation time of this melt. It is shown that these structures are characterized by a low degree of ordering and spatial localisation. It was found that up to $50$\% of the atoms in the melt can be involved in the formation of these structures. The elementary structural units of these structures are triplets of regular geometry with the characteristic lengths $3.25$ \AA~and $4.7$ \AA~as well as with the characteristic angles $45^{\circ}$ and $90^{\circ}$. The characteristic lengths of these triplets are fully consistent with correlation lengths associated with the short-range order in bismuth melt.