However, magnesium causes no change in wollastonite structure. The effect can be explained by the differences of roles of ions played in the structure. The data for the ions given by Pauling are listed in Table 5. In wollastonite structure, each Calcium ion is symmetrically surrounded by six oxygen ions and they form a regular octahedron. Although the radius of magnesium ion is much smaller than that of calcium ion, magnesium ion have the same charge and close electronegativitiy to the latter. When entering the wollastonite structure, magnesium ion will replace the position of calcium ion and form a substitutional solid solution. Since the ion radius of magnesium is smaller than that of calcium, the replacement of magnesium ion for calcium ion has no obvious effect on the crystal parameter. However, things are dierent for whitlockite. Both silicon and phosphorus are located in the center of tetrahedron formed by four oxygen ions.
However, the ion radius of silicon is greater than that of phosphorus, when silicon ion replaces phosphorus ion, it will cause distortion of the crystal structure, and lead to the increment of crystal parameter.
However, magnesium causes no change in wollastonite structure. The effect can be explained by the differences of roles of ions played in the structure. The data for the ions given by Pauling are listed in Table 5. In wollastonite structure, each Calcium ion is symmetrically surrounded by six oxygen ions and they form a regular octahedron. Although the radius of magnesium ion is much smaller than that of calcium ion, magnesium ion have the same charge and close electronegativitiy to the latter. When entering the wollastonite structure, magnesium ion will replace the position of calcium ion and form a substitutional solid solution. Since the ion radius of magnesium is smaller than that of calcium, the replacement of magnesium ion for calcium ion has no obvious effect on the crystal parameter. However, things are dierent for whitlockite. Both silicon and phosphorus are located in the center of tetrahedron formed by four oxygen ions.However, the ion radius of silicon is greater than that of phosphorus, when silicon ion replaces phosphorus ion, it will cause distortion of the crystal structure, and lead to the increment of crystal parameter.
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