Optimizing the formation of solid solutions with components of different shapes.
Optimizing the formation of solid solutions with components of different shapes.
复制标题
优化不同形状成分固溶体的形成。
DOI：
10.1063/1.4979091
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
F. Escobedo
中科院分区：
文献类型：
--
作者：
F. Escobedo
从两个不同形状的积木的共同组装中设计有序固体的一个关键挑战是预测导致最大相互有序相兼容性(MaxOC)的关键颗粒特征。虽然由组分的相对大小捕捉到的熵差异和种间能量选择性都会影响MAXOC，但前者的影响不那么直观，也是这项工作的主要焦点。利用蒙特卡罗模拟结果，对八面体和球体的硬核混合物以及以前研究过的其他混合物进行了MAXOC预测规则的制定和验证。具体地说，提出组分尺寸比应该最大化它们的“替代对称性”，从而最小化与在每个固相中将主体粒子突变为客体粒子相关的组合自由能成本。对于所考察的硬核混合物，堆积熵稳定了取代基无序的固溶体，但不能稳定化学计量化合物。因此，额外的分子模拟被用来证明，与最近的实验结果一致，这种化合物可以通过方向相关的吸引来加强物种间的相容性来形成。
A key challenge to engineer ordered solids from the co-assembly of two differently shaped building blocks is to predict the key particle characteristics that lead to maximal mutual ordered-phase compatibility (MaxOC). While both entropy disparity, as captured by the relative size of the components, and energetic inter-species selectivity affect MaxOC, it is the former whose effect is less intuitive and the main focus of this work. Such MaxOC predictive rules are formulated and validated by using Monte Carlo simulation results for hard-core mixtures of octahedra and spheres and of other previously studied mixtures. Specifically, it is proposed that component size ratios should maximize their "substitutional symmetry" and hence minimize the combined free-energy cost associated with mutating a host-particle into a guest-particle in each of the solid phases. For the hard-core mixtures examined, packing entropy stabilizes substitutionally disordered solid solutions but not stoichiometric compounds. Additional molecular simulations were hence used to demonstrate, consistent with recent experimental findings, that such compounds can be formed by strengthening the inter-species compatibility via orientation-dependent attractions.