Water, which has extremely unique properties not found in other liquids, such as the maximum density at 4 ° C and the expansion of volume during crystallization, has a great impact on meteorological, geophysical, and biological phenomena.Such anomalies are common not only in water but also in liquids such as silicon, germanium, carbon, and silica that tend to form regular tetrahedral local structures.It has been known that these liquids have directional bonds such as hydrogen bonds and covalent bonds, and their origin is that they prefer local tetrahedral symmetry.However, the relationship between the regular tetrahedron forming ability and the shape of the temperature / pressure phase diagram and the specificity of these liquids was unclear.

　For the first time, the research group succeeded in elucidating these relationships using a simulation model that can systematically change the strength of the tendency to form a regular tetrahedron structure.First, by comparing the various singularities obtained in the simulation with the predictions of the theoretical model previously proposed by the group, it can be seen that all of these anomalies are due to the formation of locally stable structures. Revealed.In addition, based on the comparison, the physical factors that govern these specificities are identified, and the physical reason why water is the most specific of these liquids (such as the maximum density anomaly). The origin was clarified.

　The results of this research are expected to greatly contribute to the systematic understanding of the specific properties of the most important substances for humankind, and are expected to have spillover effects in a wide range of fields such as life science and earth science.

Paper information:[Proceedings of the National Academy of Sciences of the United States of America] Water-like anomalies as a function of tetrahedrality