Very strong hydrogen bonds in a bent chain structure of fluorohydrogenate anions in liquid Cs(FH)F

非常に強い水素結合の発見; 液体Cs(FH)F中のフッ化水素アニオンの曲鎖構造

小原 真司*; 高田 昌樹*; 松本 一彦*; 萩原 理加*; 鈴谷 賢太郎; 森田 秀利*; Siewenie, J. E.*; Benmore, C. J.*

Kohara, Shinji*; Takata, Masaki*; Matsumoto, Kazuhiko*; Hagiwara, Rika*; Suzuya, Kentaro; Morita, Hidetoshi*; Siewenie, J. E.*; Benmore, C. J.*

液体Cs(FH)の構造を高エネルギーX線回折と中性子回折によって調べたところ、分子間の水素結合H-F距離が1.36の非常に強い水素結合を発見した。分子鎖一つあたりに含まれる平均原子数は4.4であり、液体中の分子鎖の主構造は分岐していない(FH)Fオリゴマ鎖である。この分子鎖間に非常に強いH-F水素結合によって非対称FHFが形成される。

Structure of liquid Cs(FH)F was revealed using a combination of high-energy X-ray and neutron diffraction. We found the strongest intermolecular H-F hydrogen bonds at an average distance of 1.36 are accompanied by the formation of a high degree of bending of the oligomer chain in the melt, with the gradient of F-H-F=150. A reverse Monte Carlo simulation suggested that the average number of atoms per chain is 4.4. The detailed chain analysis on the atomic configuration concluded that unbranched (FH)F oligomer chains are the major entities in the liquid and asymmetrical FHF are formed due to the strong H-F hydrogen bond. The results suggest that on average one or two HF molecules bond to each of the 11 fluorine atoms surrounding a cesium ion.