Raty Jean-Yves, Galli Giulia
Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, USA.
Nat Mater. 2003 Dec;2(12):792-5. doi: 10.1038/nmat1018. Epub 2003 Nov 23.
Nanometre-sized diamond has been found in meteorites, protoplanetary nebulae and interstellar dusts, as well as in residues of detonation and in diamond films. Remarkably, the size distribution of diamond nanoparticles seems to be peaked around 2-5 nm, and to be largely independent of preparation conditions. We have carried out ab initio calculations of the stability of nanodiamond as a function of surface hydrogen coverage and of size. We have found that at about 3 nm, and for a broad range of pressures and temperatures, particles with bare, reconstructed surfaces become thermodynamically more stable than those with hydrogenated surfaces, thus preventing the formation of larger grains. Our findings provide an explanation of the size distribution of extraterrestrial and of terrestrial nanodiamond found in ultradispersed and ultracrystalline diamond films. They also provide an atomistic structural model of these films, based on the topology and structure of 2-3-nm dimond clusters consisting of a diamond core surrounded by a fullerene-like carbon network.
在陨石、原行星星云和星际尘埃中，以及在爆炸残留物和金刚石薄膜中都发现了纳米级的钻石。值得注意的是，金刚石纳米颗粒的尺寸分布似乎在2 - 5纳米左右达到峰值，并且在很大程度上与制备条件无关。我们已经对纳米金刚石的稳定性进行了从头算计算，该稳定性是表面氢覆盖率和尺寸的函数。我们发现，在大约3纳米的情况下，对于广泛的压力和温度范围，具有裸露、重构表面的颗粒在热力学上比具有氢化表面的颗粒更稳定，从而阻止了更大颗粒的形成。我们的研究结果解释了在超分散和超结晶金刚石薄膜中发现的地外和地球纳米金刚石的尺寸分布。它们还基于由类富勒烯碳网络包围的金刚石核心组成的2 - 3纳米金刚石簇的拓扑结构和结构，提供了这些薄膜的原子结构模型。
