Molecular-scale mechanisms of crystal growth in barite
Molecular-scale mechanisms of crystal growth in barite
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DOI：
10.1038/26718
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发表时间：
1998-10-01
期刊：
影响因子：
64.8
通讯作者：
Putnis, A
中科院分区：
文献类型：
--
作者：
Pina, CM;Becker, U;Putnis, A
通过比较宏观生长动力学和各种生长机制的理论预测，已经定义了晶体生长模型（1,2）。经典的Burton-Cabrera-Frank （BCF）理论(3)预测螺旋位错的螺旋增长将在接近平衡时占主导地位。虽然这是经常观察到的（2,4），但这种生长有时被抑制（4,5），这被认为是由于杂质的存在(6)。在较高的过饱和状态下，根据“诞生和扩散”模型，生长通常是通过预先存在的表面上的二维成核来模拟的(7)。通常，生长晶体的形态是由不同晶体表面的生长速度决定的，周期性键链（PBC）理论（8,9）将这种形态与结构中存在的强键离子链联系起来。在这里，我们报告了这种重晶石晶体生长模型的测试，使用原子力显微镜在分子分辨率下对生长机制的原位观察（10,11）和生长单元表面附着的计算机模拟相结合。我们观察到二维核的强各向异性生长，其形态受底层晶体结构控制，以及结构诱导的螺旋生长的自抑制。我们的结果揭示了BCF和PBC理论在提供晶体生长的一般描述方面的局限性。
Models of crystal growth have been defined by comparing macroscopic growth kinetics with theoretical predictions for various growth mechanisms(1,2). The classic Burton-Cabrera-Frank (BCF) theory(3) predicts that spiral growth at screw dislocations will dominate near equilibrium. Although this has often been observed(2,4), such growth is sometimes inhibited(4,5), which has been assumed to be due to the presence of impurities(6). At higher supersaturations, growth is commonly modelled by two-dimensional nucleation on the pre-existing surface according to the 'birth and spread' model(7), In general, the morphology of a growing crystal is determined by the rate of growth of different crystallographic faces, and periodic-bond-chain (PBC) theory(8,9) relates this morphology to the existence of chains of strongly bonded ions in the structure. Here we report tests of such models for the growth of barite crystals, using a combination of in situ observations of growth mechanisms at molecular resolution with the atomic force microscope(10,11) and computer simulations of the surface attachment of growth units. We observe strongly anisotropic growth of two-dimensional nuclei with morphologies controlled by the underlying crystal structure, as well as structure-induced self-inhibition of spiral growth. Our results reveal the limitations of both the BCF and PBC theories in providing a general description of crystal growth.