267 / 2023-04-23 20:46:21

Folded network and structural transition in molten tin

liquid structure,,High pressure; X-ray diffraction; Phase transition

高压物理与材料科学 > 相变与机制

Liquid is a common state of condensed matter. Compared with crystalline solids, the fundamental relationships between the structure and properties of liquids are far from being well understood.^1-2 For instance, the structural origins of many liquid anomalies still remain unclear,^3-4 but liquid-liquid phase transitions (LLPT) are believed to hold a key.² Here, combining temperature-resolved X-ray diffraction, specific heat and sound velocity measurements, and advanced ab initio modeling, we show unambiguous experimental and theoretical evidence of a second-order-like LLPT in molten tin, one which favors a percolating covalent bond network at high temperatures.⁵ The observed structural transition originates from the bifurcating bonding behavior of liquids, in which chemical bonding varies continuously with bond distance, fluctuating between metallic and covalent bonding characteristics. As a result, a new paradigm of liquid structure emerges. The hidden liquid structure, in the form of a folded network, bridges two established structural models for disordered systems, i.e., the random packing of hard-spheres⁵ and a continuous random network,⁶ offering a large structural midground for liquids and glasses. Our findings provide an unparalleled physical picture of the atomic arrangement of a plethora of liquids, paving the way toward understanding the thermodynamic and dynamic anomalies of liquids but also entailing far-reaching implications for studying liquid polyamorphism.



[1]    Debenedetti, P. G. Metastable Liquids: Concepts and Principles. (Princeton University Press, 1996).

[2]    Stanley, H. E. Liquid polymorphism. (John Wiley & Sons, Inc., 2013).

[3]    Hansen, J.-P. & McDonald, I. R. Theory of Simple Liquids (Fourth Edition). (Academic Press, 2013).

[4]    Tanaka, H. Simple view of waterlike anomalies of atomic liquids with directional bonding. Phys. Rev. B 66, 064202 (2002).

[5]    Bernal, J. D. Geometry of the Structure of Monatomic Liquids. Nature 185, 68 (1960).

[6]    Zachariasen, W. H. The atomic arrangement in glass. J. Am. Chem. Soc. 54, 3841-3851 (1932).