Temperature-Dependent Structural Evolution in Au₄₄Ga₅₆ Liquid Eutectic Alloy

Abstract

Temperature-dependent short-range structural evolution of Au44Ga56 liquid eutectic alloy has been studied by in situ extended X-ray absorption fine structure (EXAFS), in situ high-energy X-ray diffraction (HEXRD) together with first-principles molecular dynamics (FPMD) simulations. It is found that the short-range structure of Au44Ga56 liquid strongly inherits the local atomic packing of the AuGa compound. A short-range structural change in Ga-centered clusters is revealed by in situ EXAFS data at the Ga K-edge at about 970 K, while no such change in Au-centered clusters appears at the Au LIII-edge. The in situ HEXRD and FPMD simulations also confirm the existence of a liquid-to-liquid crossover (LLC) in the Au44Ga56 liquid at a temperature range of about 1000–1100 K, mainly lying in the local structural change around Ga atoms. Indeed, the alloys quenched from the liquid phases below 1000 K and above 1100 K exhibit differences in structure and magnetic properties, which opens a possibility to fabricate new materials with different structures and properties in LLC-containing alloys.

Temperature-Induced Structural Changes in the Liquid GaInSn Eutectic Alloy

“…To investigate the local structure, the peak positions ( r 2 and r 3 ) of G ( r ) were extracted using a single Gaussian function to fit the symmetric second and third peaks, while it is worth noting that the mass center r 1_mc of the first peak acquired by the equation, , is examined by considering its asymmetry and the contribution of partial G ( r ). An analogous method was also reported in the literature. ,,, A deviation from the linear relationship at around 550–600 K can still be observed in r 1_mc and r 2 . However, r 3 exhibits a good linearity along the whole temperature region of 303–1373 K. The obtained results strongly indicate that an LLC may occur in the liquid GaInSn ternary eutectic alloy at around 550 K.…”

“…Initially, a cubic supercell containing 250 atoms (197 Ga, 33 In, and 20 Sn atoms) was generated with periodic boundary conditions. After fully melting and relaxing at 1500 K for more than 6000 steps to remove the memory effect of the initial configuration, the system was quenched stepwise to 1400, 1300, 1200, 1100, 1000, 900, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, and 300 K with a cooling rate of 3.33 × 10 13 K/s. ,, At each point, the box size was adjusted to make the internal pressure close to zero within ±0.5 kbar. Afterward, another 50,000 steps were performed to keep the liquid completely equilibrated and the last 4000 configurations were collected for statistical analyses.…”

“…Su et al further reported a temperature-induced LLC in two liquid noble-polyvalent metallic systems, including Ag 50 Ga 50 and Au 44 Ga 56 alloys. Apart from the XRD and AIMD results, in situ extended X-ray absorption fine structure measurements were first used to characterize the liquid structure of the Au 44 Ga 56 alloy, confirming the existence of a structural crossover at a temperature range of around 1000–1100 K that was mainly caused by the local structural change around Ga atoms . Motivated by these results, in this work, we further investigate the temperature-dependent liquid structure of a Ga–In–Sn ternary eutectic alloy by in situ high-temperature synchrotron XRD, thermal expansion, and heat capacity measurements together with AIMD simulations.…”

“…Later, Yu et al 28 extended the studies of liquid structure into the binary GaIn eutectic alloy and found that the LLC takes place at around 400−550 K, which was suggested to originate from the segregation of In atoms at low temperatures. Su et al further reported a temperature-induced LLC in two liquid noble-polyvalent metallic systems, including Ag 50 Ga 50 29 and Au 44 Ga 56 30 alloys. Apart from the XRD and AIMD results, in situ extended X-ray absorption fine structure measurements were first used to characterize the liquid structure of the Au 44 Ga 56 alloy, confirming the existence of a structural crossover at a temperature range of around 1000−1100 K that was mainly caused by the local structural change around Ga atoms.…”

“…Apart from the XRD and AIMD results, in situ extended X-ray absorption fine structure measurements were first used to characterize the liquid structure of the Au 44 Ga 56 alloy, confirming the existence of a structural crossover at a temperature range of around 1000−1100 K that was mainly caused by the local structural change around Ga atoms. 30 Motivated by these results, in this work, we further investigate the temperature-dependent liquid structure of a Ga−In−Sn ternary eutectic alloy by in situ hightemperature synchrotron XRD, thermal expansion, and heat capacity measurements together with AIMD simulations. It is found that the studied liquid GaInSn ternary eutectic alloy showed an anomalous heat capacity peak at around 520 K, indicating a possible LLC, which was further supported by density measurements and structural analyses.…”