arXiv subjects

Yukio Kajihara

Publications and source records attributed to Yukio Kajihara.

5 recordsLinked to original sources

arXiv2026

Experimental Observation of Mesoscopic Dynamic Fluctuations in Water-Alcohol Mixtures

We applied a dynamic fluctuation measurement method to liquid water-methanol mixtures over a wide range of compositions and temperatures. This method, which we developed in recent years, combines ultrasonic and inelastic X-ray scattering techniques to detect mesoscopic-level fluctuations-that is, the degree of heterogeneity-in liquids using sound waves. The results showed that the strength of dynamic fluctuations increased as the alcohol composition decreased and as the temperature decreased. This trend was also observed in water-ethanol and water-glycerol mixtures. From these results, we concluded that the origin of these fluctuations lies in the low-temperature (supercooled) region of water alone, and that mixing with alcohol eliminates the dynamic fluctuations. This conclusion-that mixing substances reduces fluctuations or heterogeneity-may seem strange at first glance, but it is actually consistent with the framework of the liquid-liquid phase transition hypothesis, which explains the thermodynamic anomalies of water. It also aligns with the results of our recent measurements of the strength of dynamic fluctuations in water across a wide range of temperature and pressure conditions. It has long been known that various thermodynamic anomalies exist in water-alcohol mixtures at low compositions, and while there have been various discussions on this topic in the past, our current findings offer a new perspective on these discussions.

cond-mat.soft↗

arXiv2024

Experimental Observation of Maximum Density Fluctuation in Liquid Te

We performed small-angle X-ray scattering measurements of liquid Te using a synchrotron radiation facility and observed the maximum scattering intensity near 620 K in the supercooled region (melting temperature 723 K). This result is an experimental observation of the ridge line of the critical density fluctuation associated with the liquid-liquid phase transition that is argued to exist in the supercooled region and verifies the existence of the transition. Similar results have been reported for supercooled liquid water, demonstrating the universality of the liquid-liquid transition concept (or inhomogeneous model) in explaining the thermodynamics of these "anomalous liquids". Moreover, as a more essential issue, it has been demonstrated that liquids can be inhomogeneous at mesoscopic scales, even in their thermal equilibrium state. This will contribute to a greater understanding of the physics of liquids, including glass-forming liquids.

cond-mat.soft↗

arXiv2023

Experimental Observation of Mesoscopic Fluctuations to Identify Origin of Thermodynamic Anomalies of Ambient Liquid Water

We report a new experimental approach for observing mesoscopic fluctuations underlying the thermodynamic anomalies of ambient liquid water. In this approach, two sound velocity measurements with different frequencies, namely inelastic X-ray scattering (IXS) in THz band and ultrasonic (US) in MHz band, are required to investigate the relaxation phenomenon with the characteristic frequency between the two aforementioned frequencies. We performed IXS measurements to obtain the IXS sound velocity of liquid water from the ambient conditions to the supercritical region of liquid-gas phase transition (LGT) and compared the results with the US sound velocity in the literature. We found that the ratio of the two sound velocities, Sf, which corresponds to the relaxation intensity, exhibits a simple but significant change. Two distinct rises were observed in the high-temperature and low-temperature regions, implying that two relaxation phenomena exist: in the high-temperature region, a peak was observed near the LGT critical ridge line, which was linked with changes in the density fluctuation and isochoric and isobaric specific heat capacities; in the low-temperature region, Sf increased toward the low-temperature region, which was linked with the change in the isochoric heat capacity. We concluded that these two relaxation phenomena are originated from critical fluctuations of liquid-gas phase transition (LGT) and liquid-liquid phase transition, respectively. The linkage between Sf and isochoric heat capacity in the low-temperature region proves that the relaxation is the cause of the well-known heat capacity anomaly of ambient liquid water. In this study, both LGT and LLT critical fluctuations were observed, and the relationship between thermodynamics and the critical fluctuations was comprehensively discussed.

cond-mat.soft↗

arXiv2022

Structural changes across thermodynamic maxima in supercooled liquid tellurium: a water-like scenario

Liquid polymorphism is an intriguing phenomenon which has been found in a few single-component systems, the most famous being water. By supercooling liquid Te to more than 130 K below its melting point and performing simultaneous small-angle and wide-angle X-ray scattering measurements, we observe clear maxima in its thermodynamic response functions around 615 K, suggesting the possible existence of liquid polymorphism. A close look at the underlying structural evolution shows the development of intermediate-range order upon cooling, most strongly around the thermodynamic maxima, which we attribute to bond-orientational ordering. The striking similarities between our results and those of water, despite the lack of hydrogen-bonding and tetrahedrality in tellurium, indicate that water-like anomalies may be a general phenomenon among liquid systems with competing bond- and density-ordering.

cond-mat.soft↗

arXiv2020

Furnace for Inelastic X-Ray Scattering from Liquids to 1600C

The design and implementation of a furnace for inelastic x-ray scattering from liquids with sample temperatures up to ~1600C is described. Carbon composite heaters operating in vacuum provide robust heating elements: one pair of heaters has been used for >18 days of operational time above 1500C, including 8 cycles to room temperature. High quality data has been obtained to scattering angles as low as 7 mrad in two-theta (Q<1 nm-1 at 25.7 keV) from a sample at 1560C.

physics.ins-det↗