The speculation of superdiamonds

Abstract

Diamond has the highest bond energy per unit volume of all known materials, and hence it is assumed to possess the highest hardness. The hardness of diamond comes from its small atoms that form four covalent bonds. To make a structure harder than diamond, its atoms must be smaller than carbon, and/or these atoms must form at least four covalent bonds. The first consideration would be to strike off all elements with period number higher than 2. The second criterion would be to eliminate all elements lighter than carbon. Hence, only carbon, nitrogen, oxygen, fluorine, and neon are possible candidates for superdiamond. However, in order to become a superdiamond, these elements must form monatomic structures with coordination number higher than 4. Moreover, no lone pair electrons are allowed, so all their valence electrons must be involved in single covalent bonds. The number of valence electrons in simple cubic carbon is less than the coordination number of 6. As a result, the bonds may turn metallic, so it may not be as hard as diamond. Potential superdiamond structures include diamond-like nitrogen, simple cubic oxygen or fluorine, and body centred cubic (bcc) neon. If these elements can form single covalent bonds that involve all their valence electrons, they could become superdiamond. Otherwise, the hardness of diamond may be as insurmountable as the speed of light, diamond. The above hypothetical structures of superdiamond may be synthesised by directing collimated beams of single ions that are converging from the intended directions aiming at a common centre. Such a technique was developed by Nobel Laureate Y T Lee decades ago. The possible instantaneous formation of the predicted hypothetical structures, even though they may be highly metastable, can be studied in situ by laser strobe light flashed for femtoseconds. Such femtochemistry has already been invented by Ahmed Zewail, the latest Nobel Laureate.