Crystal Structure of 3MgO·2CO2 Solved by Monte Carlo Simulation

Kohei WATABEa, Yusuke SETOb and Hiroyuki MIURAa*

aDepartment of Natural History Sciences, Graduate School of Science, Hokkaido University
N10W8, Kita-ku, Sapporo 060-0810, Japan
bDepartment of Earth and Planetary Science, Kobe University
1-1, Rokkoudai, Nada-ku, Kobe, 657-8501, Japan

(Received: March 10, 2009; Accepted for publication: October 15, 2009)

  The crystal structure of the intermediate phase (3MgO·2CO2) of synthetic nesquehonite (MgO·3H2O) following heat treatment was solved by Monte Carlo simulation using powder X-ray diffraction data and was confirmed by Rietveld refinement. The phase is cubic with space group I43m and cell constants of a = 8.516(13) A. The unit cell consists of independent atoms such as magnesium, carbon, and two oxygen atoms. The magnesium atom is surrounded by six oxygen atoms in octahedral coordination, and four symmetrically identical MgO6 octahedra in a edge-sharing arrangement form an Mg4O17 block in the (100) planes of a unit cell. These Mg4O17 blocks share edges with other Mg4O17 blocks to form a framework structure. A CO3 triangle that exists on the three-fold axis connects three Mg4O17 blocks.

キーワード: Intermediate phase, 3MgO.2CO2, Crystal structure, Monte Carlo simulation, Nesquehonite

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