Abstract
Density functional theory calculations were performed to analyze atomic and electronic structures of cordierite. The most stable configuration of Al and Si atoms in the six-membered ring of a unit cell was decided by geometry optimizations for sixteen different initial structures. A correlation was observed between the number of Al-O-Al bonds in a unit cell and the lattice energy. We concluded that the number of Al-O-Al bonds is a determining factor of the lattice stability. The structural parameters of the most stable crystal structure obtained by geometry optimization agreed well with the experimental observation. According to the distribution of atomic charges and analysis of bond order, the followings were clarified: (i) the covalent bond in a T1 tetrahedron was stronger than that in a T2 tetrahedron, (ii) the covalent bond of a cation in six-membered ring with O atoms in a T1 tetrahedron was the weakest, and (iii) Mg in the cordierite is of ionic nature.
