Determination of the local structure of a cage with an oxygen ion in Ca12Al14O33

作者：Sakakura Terutoshi; Tanaka Kiyoaki^*; Takenaka Yasuyuki; Matsuishi Satoru; Hosono Hideo; Kishimoto Shunji

来源：Acta Crystallographica Section B-Structural Science, 2011, 67(3): 193-204.

DOI：10.1107/S0108768111005179

• mayenite
• local structure
• occupied cage
• cage distortion
• electrostatic potential

The crystal structure of mayenite (12CaO center dot 7Al(2)O(3)) has been investigated by single-crystal synchrotron diffraction with high resolution and accuracy, using a four-circle diffractometer equipped with an avalanche photodiode detector (APD) detector installed at PF14A in Tsukuba, Japan. Analysis revealed random displacements of ions by the electrostatic force of the O2- ion (O3) clathrated in two out of 12 cages. O3 ions are located at general positions close to the <file type="gif" name="ayb_og5045_mu1.gif"/> site at the centre of each cage. The difference-density map revealed two large peaks corresponding to displaced Ca ions. The positive ions close to O3 are displaced and one-to-one correspondence was found between one of the four equivalent O3 ions and the displaced ions. When an O3 ion is present in the cage the Al ion at the 16c position moves 0.946 (3) A toward the O3 ion. One of the Al-O bonds is broken and a new Al-O3 bond is created. The result is an AlO4 tetrahedron that is quite deformed. The three O1 ions and the O2 ion of the destroyed AlO4 tetrahedron are forcibly displaced. O1 and O2 have two and one displaced ions, respectively. The local structure of the cage occupied by one of the four O3 ions was determined by calculating the electrostatic potential and electric field in the deformed cage, although the position of one of the displaced O1 ions was not clearly identified.

• 出版日期2011-6