X-Ray Diffraction of the First Man-made Diamonds

This is a copy of the X-ray diffraction pattern of the first diamonds made by man. This photo documents the culmination of 150 years of attempts to transform graphite into diamond.   Other  efforts had resulted in oxides of aluminum and various other "fool's gold" imitations of diamond.  The patterns on this photo provided GE with  definitive proof that the substance that Tracy Hall synthesized on December 16, 1954, was in fact diamond. 

Every crystal is made up of atoms grouped in lattices with the inter-atomic distance varying with the orientation.  Cross sections of different planes will show various densities of the atoms depending on the orientation of the cutting plane, much like the density of trees in the rows of an orchard depends on the angle from which the trees are  viewed.  

The film that records the deflection of the X-rays is wrapped around the sample specimen in a semicircle with the X-rays entering at the dark circle on the left side of the picture and exiting through the the similar circle on the right.  The point halfway between represents a diffraction 90° from the path of the X-ray beam.

As the X-rays strike atoms in the sample they are deflected at specific angles depending on the density of the atoms in the path.  By measuring the distance of the rays transferred to film (and thereby the angle of the X-ray deflection) scientists can determine the lattice structure of the substance in question.

Diamond is a very symmetric crystal and exhibits few lines of diffraction compared to less ordered crystals.  The atoms in a diamond crystal are arranged in tetrahedrons (close-packed hexagonal) with the interstitial distances being equal.  In addition, synthetic diamond exhibits certain other "satellite" spots that distinguish it from natural diamond.

 

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