NANOMETRE-SIZED DIAMONDS ARE MORE STABLE THAN GRAPHITE
NANOMETRE-SIZED DIAMONDS ARE MORE STABLE THAN GRAPHITE
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DOI：
10.1038/343244a0
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发表时间：
1990-01-18
期刊：
影响因子：
64.8
通讯作者：
GREINER, NR
中科院分区：
文献类型：
--
作者：
BADZIAG, P;VERWOERD, WS;GREINER, NR
最近从爆炸的碳质残留物中回收了直径仅为3-5纳米的钻石。它们也在陨石2中发现，在气相3中均匀成核，在低压氢气4中可以生长出类金刚石薄膜。这四种情况的情况非常不同，但陨石和爆炸的大小几乎相同，而且人造钻石的生长需要成核中心，这表明存在一个共同的潜在因素。超小钻石太小而不容易被发现，实际上可能比目前认识到的要普遍得多。我们通过比较小的四面体(钻石)和六角形(石墨)团簇的形成热得出这一结论。与Nuth关于星际介质中钻石的讨论一致，我们得出结论，表面能是微晶钻石稳定化的一个重要方面。对于氢原子终止的表面键，我们发现直径小于∼3 nm的钻石在能量上比多环芳烃(石墨的前体)更受青睐，而不是与钻石通常相关的高压或极端动力学条件。
DIAMONDS just 3–5 nm in diameter have recently been recovered from carbonaceous residues of detonations1. They have also been found in meteorites2, nucleate homogeneously in the gas phase3, and diamond-like films can be grown in low-pressure hydrogen4. Conditions are very different in these four cases, but the nearly equal sizes in both meteorites and detonations, and the necessity of nucleation centres for growth of synthetic diamonds, indicate the existence of a common underlying factor. Ultra-small diamonds, too small to be detected readily, may in fact be far more prevalent than presently realized. We arrive at this conclusion by comparing calculated heats of formation of small tetrahedral (diamond) and hexagonal (graphitic) clusters. In agreement with Nuth's discussions on diamonds in interstellar media5,6, we conclude that surface energies are an important aspect in the stabilization of microcrystalline diamonds. For surface bonds terminated with hydrogen atoms, we find that diamonds smaller than ∼3 nm in diameter are energetically favoured over polycyclic aromatics (the precursors to graphite), withou/equiring the high pressures or extreme kinetic conditions usually associated with diamonds.