Modified Phases of Diamond Formed Under Shock Compression and Rapid Quenching

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Science  16 Aug 1991:
Vol. 253, Issue 5021, pp. 772-774
DOI: 10.1126/science.253.5021.772


Two modified forms of carbon were quenched by a rapid-cooling technique from graphite sheets shock-compressed to 65 gigapascals and 3700 K. One form, ``n-diamond," which was obtained from the most rapidly cooled part, has a crystal structure close to that of cubic diamond. The other form, found in the relatively slow-cooled part, was comparable to an i-carbon prepared by an ion-beam technique. The n-diamond is interpreted as a metastable form, the same as hexagonal diamond, converted from graphite through a martensitic transition, for which either the region or the path may be different from that of hexagonal diamond. The second form was found to be produced through reconstruction.