The structure of high-temperature liquids is an important topic for understanding the fragility of liquids. Here we report the structure of a high-temperature non-glass-forming oxide liquid, ZrO2, at an atomistic and electronic level. The Bhatia–Thornton number–number structure factor of ZrO2 does not show a first sharp diffraction peak. The atomic structure comprises ZrO5, ZrO6 and ZrO7 polyhedra with a significant contribution of edge sharing of oxygen in addition to corner sharing. The variety of large oxygen coordination and polyhedral connections with short Zr–O bond lifetimes, induced by the relatively large ionic radius of zirconium, disturbs the evolution of intermediate-range ordering, which leads to a reduced electronic band gap and increased delocalization in the ionic Zr–O bonding. The details of the chemical bonding explain the extremely low viscosity of the liquid and the absence of a first sharp diffraction peak, and indicate that liquid ZrO2 is an extremely fragile liquid.

The structure of glassy, liquid, and amorphous materials is still not well understood, due to the insufficient structural information from diffraction data. In this article, attempts are made to understand the origin of diffraction peaks, particularly of the first sharp diffraction peak (FSDP, Q 1), the principal peak (PP, Q 2), and the third peak (Q 3), observed in the measured diffraction patterns of disordered materials whose structure contains tetrahedral motifs. It is confirmed that the FSDP (Q 1) is not a signature of the formation of a network, because an FSDP is observed in tetrahedral molecular liquids. It is found that the PP (Q 2) reflects orientational correlations of tetrahedra. Q 3 , that can be observed in all disordered materials, even in common liquid metals, stems from simple pair correlations. Moreover, information on the topology of disordered materials was revealed by utilizing persistent homology analyses. The persistence diagram of silica (SiO 2) glass suggests that the shape of rings in the glass is similar not only to those in the crystalline phase with comparable density (¡-cristobalite), but also to rings present in crystalline phases with higher density (¡-quartz and coesite); this is thought to be the signature of disorder. Furthermore, we have succeeded in revealing the differences, in terms of persistent homology, between tetrahedral networks and tetrahedral molecular liquids, and the difference/similarity between liquid and amorphous (glassy) states. Our series of analyses demonstrated that a combination of diffraction data and persistent homology analyses is a useful tool for allowing us to uncover structural features hidden in halo pattern of disordered materials.

Mitochondrial DNA variation in the cytochrome b (cyt b) gene and the control region was examined in the red fox Vulpes vulpes from Japan, with special focus on the population divergence between Hokkaido and northern Honshu. Resultant haplotypes from Hokkaido were subdivided into two distinct groups (I and II), with an average genetic distance of 0.027 for cyt b. Divergence time is roughly estimated to be 1-2 million years ago, given that the conventional divergence rate of the mammalian cyt b gene is 2% per million years. Notably, Group II was only found in Hokkaido, whereas Group I comprised haplotypes from Honshu, Kyushu (Japan), eastern Russia, and Europe, as indicated by a comparison of our own data to the literature. On the other hand, judging from constructed trees, Group I haplotypes from Hokkaido appeared to differ from those from other parts of Japan, i.e., Honshu and Kyushu. This implies that Blakiston's Line, which demarcates the boundary between Hokkaido and Honshu, has been an effective barrier and has allowed the structuring of genetic variation in maternal lineages. Thus, these results suggest that the Hokkaido population, which is sometimes referred to as the distinct subspecies V. v. schrencki, has its own genetic background with multiple migration events and differs from the parapatric subspecies V. v. japonica found in Honshu and Kyushu.

X-ray diffraction and density measurements have been simultaneously performed to investigate the atomic structure of molten silicon in a wide temperature range including the undercooling region by using the electromagnetic levitation technique. The density was obtained from the mass and the shape of a levitated sample by a non-contact method based on the image analysis technique. X-ray diffraction experiments were performed by using the synchrotron radiation at SPring8, Japan. From structural analysis of undercooled molten silicon, the first nearest neighbour coordination numbers and interatomic distances were about 5 and 2.48 Å with no dependence on temperature in the range of 1900–1550 K. We conclude as a result that the short-range order based on tetrahedral bonds of undercooled molten silicon does not change with the degree of undercooling but that medium-range order changes by the degree of undercooling.

Understanding the liquid structure provides information that is crucial to uncovering the nature of the glass-liquid transition. We apply an aerodynamic levitation technique and high-energy X-rays to liquid (l)-Er 2 O 3 to discover its structure. The sample densities are measured by electrostatic levitation at the International Space Station. Liquid Er 2 O 3 displays a very sharp diffraction peak (principal peak). Applying a combined reverse Monte Carlomolecular dynamics approach, the simulations produce an Er-O coordination number of 6.1, which is comparable to that of another nonglass-forming liquid, l-ZrO 2. The atomic structure of l-Er 2 O 3 comprises distorted OEr 4 tetraclusters in nearly linear arrangements, as manifested by a prominent peak observed at~180°in the Er-O-Er bond angle distribution. This structural feature gives rise to long periodicity corresponding to the sharp principal peak in the X-ray diffraction data. A persistent homology analysis suggests that l-Er 2 O 3 is homologically similar to the crystalline phase. Moreover, electronic structure calculations show that l-Er 2 O 3 has a modest band gap of 0.6 eV that is significantly reduced from the crystalline phase due to the tetracluster distortions. The estimated viscosity is very low above the melting point for l-ZrO 2 , and the material can be described as an extremely fragile liquid.

A molecular liquid GeI4 is a candidate that undergoes a pressure-induced liquid-to-liquid phase transition. This study establishes the reference structure of the low-pressure liquid phase. Synchrotron x-ray diffraction measurements were carried out at several temperatures between the melting and the boiling points under ambient pressure. The molecule has regular tetrahedral symmetry, and the intramolecular Ge-I length of 2.51 Å is almost temperature-independent within the measured range. A reverse Monte Carlo (RMC) analysis is employed to find that the distribution of molecular centers remains self-similar against heating, and thus justifying the length-scaling method adopted in determining the density. The RMC analysis also reveals that the vertex-to-face orientation of the nearest molecules are not straightly aligned, but are inclined at about 20 degrees, thereby making the closest intermolecular I-I distance definitely shorter than the intramolecular one. The prepeak observed at  ∼1 Å(-1) in the structural factor slightly shifts and increases in height with increasing temperature. The origin of the prepeak is clearly identified to be traces of the 111 diffraction peak in the crystalline state. The prepeak, assuming the residual spatial correlation between germanium sites in the densest direction, thus shifts toward lower wavenumbers with thermal expansion. The aspect that a relative reduction in molecular size associated with the volume expansion is responsible for the increase in the prepeak's height is confirmed by a simulation, in which the molecular size is changed.

With the advent of third-generation synchrotron sources and the development of light source techniques, X-ray scattering techniques have become feasible, leading to new approaches for studying the structures of disordered materials in a quantitative manner. We introduce a dedicated diffractometer for high-energy total X-ray scattering measurement and a newly developed anomalous X-ray spectrometer at SPring-8. As advanced methodologies for the measurement of liquids, we now offer three state-of-art levitation instruments for aerodynamic levitation, electrostatic levitation, and acoustic levitation at the SPring-8 beamlines, covering a wide temperature range of −40–3000 ℃. Furthermore, scientific investigations of glasses, liquids, and amorphous materials reported in the last five years at SPring-8 are reviewed.

High-energy X-ray diffraction experiments were performed for a metallic glass-forming Zr 70 Cu 30 alloy in the liquid state at a high temperature. Conical nozzle levitation was applied as a containerless method of obtaining accurate structure information of a highly reactive melt. The total structure factor obtained for the liquid alloy above its melting point shows a particular shoulder on the second peak, which is probably an indication of local icosahedral short-range ordering typically observed in deeply undercooled liquids. This implies that short-range ordered clusters already exist even in the equilibrium liquid state of Zr-based metallic glass-forming alloys.