Travaille A Markus, Steijven Erica G A, Meekes H, van Kempen Herman
IMM, Department of Solid State Physics and Department of Solid State Chemistry, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
J Phys Chem B. 2005 Mar 31;109(12):5618-26. doi: 10.1021/jp0446128.
Classical heterogeneous nucleation theory is used to describe the epitaxial nucleation of calcite on self-assembled monolayers (SAMs). Both spherical and faceted clusters are considered. The use of faceted clusters reveals a useful relation between the shape of very small crystals and the ratio of the heterogeneous and homogeneous nucleation barriers. The experimental approach of this paper concerns the measurement of the threshold driving forces for both homogeneous and heterogeneous nucleation of calcite. This is accomplished by preparing solutions with well-defined driving forces and by measuring the resulting types of nucleation that are observed after a fixed experimental time. The results of the experiments and the theoretical shape analysis are compared, and it is shown that in the experiments no homogeneous nucleation of calcite occurs for driving forces up to at least Deltamu/k(B)T approximately equal to 6.0. A calculation of the critical cluster size for heterogeneous nucleation results in a range of 2-28 growth units and faceted critical clusters from 3-28 growth units, depending on the value of the surface free energy of calcite. These sizes are 50-100 times smaller than the crystalline domain sizes of SAMs and therefore small enough to explain the promoting effect of the substrate.
经典的非均相成核理论用于描述方解石在自组装单分子层（SAMs）上的外延成核。同时考虑了球形和多面体团簇。使用多面体团簇揭示了非常小的晶体形状与非均相和均相成核势垒之比之间的有用关系。本文的实验方法涉及测量方解石均相和非均相成核的阈值驱动力。这是通过制备具有明确驱动力的溶液并测量在固定实验时间后观察到的成核类型来实现的。将实验结果与理论形状分析进行了比较，结果表明，在实验中，对于高达至少Δμ/k(B)T约等于6.0的驱动力，方解石不会发生均相成核。根据方解石表面自由能的值，非均相成核的临界团簇尺寸计算结果在2 - 28个生长单元范围内，多面体临界团簇尺寸在3 - 28个生长单元范围内。这些尺寸比SAMs的晶畴尺寸小50 - 100倍，因此小到足以解释基底的促进作用。
