Elucidation of the microscopic mechanism that induces liquid-liquid transition

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K05581
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Mathematical physics/Fundamental condensed matter physics
• Research Institution: Ehime University
• Principal Investigator: Fuchizaki Kazuhiro 愛媛大学, 理工学研究科(理学系), 教授 (10243883)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: 液－液転移 / 第二臨界点 / ポリアモルフィズム / 局所構造 / ヨウ化ゲルマニウム / ヨウ化錫 / XAFS / 6－6方式

Outline of Final Research Achievements

The foremost achievement of the present study is experimentally finding the symmetry lowering of tin tetraiodide and germanium tetraiodide molecules from Td to C3v upon the liquid-liquid transition and crossover, respectively. This finding was ultimately an unexpected consequence. The symmetry lowering induces the two different characteristic lengths to the intermolecular interaction, thereby making the intermolecular potential possess two minima. The two stable states in the potential should be responsible for the appearance of two liquid states with different densities. This investigation aimed to identify the way of coupling between the global (thermodynamic) and local order parameters. However, the essential feature that the local free energy should capture is not the coupling but the appearance of a new stable state upon a liquid-liquid transition.

Free Research Field

統計力学・物性基礎論分野

Academic Significance and Societal Importance of the Research Achievements

液－液転移、とりわけ、第二臨界点の存在は気－液相に対する既存の捉え方の再考を迫るものである。これらの相において熱力学的な秩序変数は密度のみである。局所(配向)秩序が断熱消去できる場合、臨界点異常は究極的には大域秩序(密度)揺らぎのみに由来することになる。しかし、そうでない場合は両方の秩序を同等に扱わなければならない。「状況証拠」からではなく、直接観測を通じて正しい理論を導くことが重要である。ヨウ化錫はポリアモルフィズム研究面で水の代替物質になり得るという点よりも実際に臨界領域を観測できる点を強調したい。