Very sharp diffraction peak in nonglass-forming liquid with the formation of distorted tetraclusters
Koyama, Chihiro; Tahara, Shuta; Kohara, Shinji; Onodera, Yohei; Småbråten, Didrik Rene; Selbach, Sverre Magnus; Akola, Jaakko; Ishikawa, Takehiko; Masuno, Atsunobu; Mizuno, Akitoshi; Okada, Junpei T.; Watanabe, Yuki; Nakata, Yui; Ohara, Koji; Tamaru, Haruka; Oda, Hirohisa; Obayashi, Ippei; Hiraoka, Yasuyuki; Sakata, Osami
Peer reviewed, Journal article
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Original versionNPG Asia Materials. 2020, 12 . 10.1038/s41427-020-0220-0
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)-Er2O3 to discover its structure. The sample densities are measured by electrostatic levitation at the International Space Station. Liquid Er2O3 displays a very sharp diffraction peak (principal peak). Applying a combined reverse Monte Carlo – molecular dynamics approach, the simulations produce an Er–O coordination number of 6.1, which is comparable to that of another nonglass-forming liquid, l-ZrO2. The atomic structure of l-Er2O3 comprises distorted OEr4 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-Er2O3 is homologically similar to the crystalline phase. Moreover, electronic structure calculations show that l-Er2O3 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-ZrO2, and the material can be described as an extremely fragile liquid.