The role that additives play in the growth of sodium chloride is a topic which has been widely researched but not always fully understood at an atomic level. Lead chloride (PbCl₂) is one such additive which has been reported to have growth inhibition effects on NaCl {100} and {111}; however, no definitive evidence has been reported which details the mechanism of this interaction. In this investigation, we used the technique of surface x-ray diffraction to determine the interaction between PbCl₂ and NaCl {100} and the structure at the surface. We find that Pb²⁺ replaces a surface Na⁺ ion, while a Cl⁻ ion is located on top of the Pb²⁺. This leads to a charge mismatch in the bulk crystal, which, as energetically unfavourable, leads to a growth blocking effect. While this is a similar mechanism as in the anticaking agent ferrocyanide, the effect of PbCl₂ is much weaker, most likely due to the fact that the Pb²⁺ ion can more easily desorb. Moreover, PbCl₂ has an even stronger effect on NaCl {111}.

中文翻译：

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NaCl {100}表面上的PbCl2的结构及其对晶体生长的影响

添加剂在氯化钠生长中的作用是一个广泛研究的话题，但在原子水平上并不总是被完全理解。氯化铅（PbCl ₂）是一种这样的添加剂，据报道对NaCl {100}和{111}具有生长抑制作用。但是，没有确切的证据报道这种相互作用的机理。在这项研究中，我们使用了表面X射线衍射技术来确定PbCl ₂和NaCl {100}之间的相互作用以及表面结构。我们发现，铅²⁺取代了表面的Na ⁺离子，而氯^-离子位于铅的顶部²⁺。这导致块状晶体中的电荷失配，这在能量上不利，从而导致生长阻挡作用。尽管这是与抗结块剂亚铁氰化物相似的机理，但PbCl ₂的作用要弱得多，这很可能是由于Pb ²⁺离子更容易解吸的事实。而且，PbCl ₂对NaCl {111}具有甚至更强的作用。