Last Update 28/ 01/ 2002
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The application above allow you to rotate continually the projection in perspective of the cubic unit cell of type F of the gold crystal around one of the axes of order 4, by dragging the green square with the mouse. Pre-determined rotations will be observed after clicking on 0o , 90o , up to 360o. Two points stay stationary during the rotation due to its localization over the rotation axe.
It is observed that the gold's unit cell contain 4 lattice points, resulting from the sum of 1/8 of a point on each corner and 1/2 of a point on each face centre. Each lattice point contains one atom of gold represented by a yellow sphere. The density calculated from the molar mass of gold (196.97 g) and from the unit cell edge, which is determined by x-ray diffraction [1] as being 4.0786 A (or 0.4078 6 nm), results in 19.28 g/mL, equal to the density of gold 99.997% pure.
Bibliography
1. L.G. Berry (Editor), Selected Powder Diffraction Data for Minerals, Joint Committee on Powder Diffraction Standards, Pennsylvania, 1974.
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