Longone Pablo Jesús, Ramirez-Pastor Antonio José
Departamento de Física, Instituto de Física Aplicada, Universidad Nacional de San Luis-CONICET, Ejército de Los Andes 950, San Luis D5700BWS, Argentina.
Entropy (Basel). 2025 Aug 10;27(8):849. doi: 10.3390/e27080849.
Adsorption of multicomponent mixtures on solid substrates is essential to numerous technological processes and provides key insights into surface phenomena. Despite advancements in theoretical modeling, many approaches still assume that each adsorbate occupies a single site, thereby neglecting important effects arising from molecules that span multiple adsorption sites. In this work, we broaden the theoretical description of such systems by considering the adsorption of distinct polyatomic species on triangular lattices. Our approach is based on (i) exact thermodynamic results for polyatomic gases on one-dimensional lattices, extended here to account for substrates with higher coordination numbers, and (ii) the "0D cavity" functional theory originally developed by Lafuente and Cuesta, which reduces to the well-known Guggenheim-DiMarzio model in the limit of rigid rods. As a case study, we explore the behavior of a three-component system consisting of dimers, linear trimers, and triangular trimers adsorbing onto a triangular lattice. This model captures the interplay between structural simplicity, multisite occupancy, configurational diversity, and competition for space, key factors in many practical scenarios involving size-asymmetric molecules. We characterize the system using total and partial isotherms, energy of adsorption, and configurational entropy of the adsorbed phase. To ensure the reliability of our theoretical predictions, we perform Monte Carlo simulations, which show excellent agreement with the analytical approaches. Our findings demonstrate that even complex adsorption systems can be efficiently described using this generalized framework, offering new insights into multicomponent surface adsorption.
多组分混合物在固体基质上的吸附对于众多技术过程至关重要，并为表面现象提供了关键见解。尽管理论建模取得了进展，但许多方法仍然假设每个吸附质占据单个位点，从而忽略了跨越多个吸附位点的分子所产生的重要影响。在这项工作中，我们通过考虑不同多原子物种在三角形晶格上的吸附来拓宽此类系统的理论描述。我们的方法基于：（i）一维晶格上多原子气体的精确热力学结果，在此扩展以考虑具有更高配位数的基质；（ii）最初由拉富恩特和库埃斯塔开发的“零维腔”泛函理论，在刚性棒的极限情况下简化为著名的古根海姆 - 迪马尔齐奥模型。作为一个案例研究，我们探索了由二聚体、线性三聚体和三角形三聚体吸附到三角形晶格上组成的三元系统的行为。该模型捕捉了结构简单性、多位点占据、构型多样性和空间竞争之间的相互作用，这些是许多涉及尺寸不对称分子的实际场景中的关键因素。我们使用总等温线和部分等温线、吸附能以及吸附相的构型熵来表征该系统。为确保我们理论预测的可靠性，我们进行了蒙特卡罗模拟，其与分析方法显示出极好的一致性。我们的研究结果表明，即使是复杂的吸附系统也可以使用这个广义框架有效地描述，为多组分表面吸附提供了新的见解。
