Structural-electronic relationships in inorganic solids: powder neutron diffraction studies of the rutile and anatase polymorphs of titanium dioxide at 15 and 295 K
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Rietveld analysis of time-of-flight pulsed neutron diffraction of powders shows a nearly isotropic shrinkage of the structures of both the rutile and anatase polymorphs of Ti02upon cooling from 295 to 15 K and no change in the sense of the distortion of the Ti06octahedra (two long and four short Ti-0 distances in both): rutile at 295 (first) and 15 K (second), a04.593 08 (4), 4.586 66 (4), c0, 2.958 89 (3), 2.95407 (3), xoxygen, 0.304 76 (6), 0.304 69 (6), Ti-0(4X), 1.9486 (3), 1.9459 (3), Ti-0(2X), 1.9796 (4), 1.9764 (4); anatase at 295 and 15 K, a0, 3.784 79 (3), 3.782 16 (3), c0, 9.502 26 (12), 0.50465 (12), xoxygen, 0.166 86 (5), 0.16675 (4), Ti-0(4X), 1.9338 (1), 1.9322 (1), Ti-0(2X), 1.9799 (5), 1.9788 (4): all distances referenced to silicon (a - 5.430 88 A). Both tight-binding calculations on the crystalline solids and molecular mechanics computations on the oxide lattice alone lead to a model in which the balance of attractive Ti-0 and repulsive 00 interactions control the details of the overall structures. The relative bond lengths around metal centers in some other systems are predicted. 1987, American Chemical Society. All rights reserved.
