Wittmann René, Smallenburg Frank, Brader Joseph M
Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland.
Institut für Theoretische Physik II, Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany.
J Chem Phys. 2019 May 7;150(17):174908. doi: 10.1063/1.5086390.
We explore the pressure of active particles on curved surfaces and its relation to other interfacial properties. We use both direct simulations of the active systems as well as simulations of an equilibrium system with effective (pair) interactions designed to capture the effects of activity. Comparing the active and effective passive systems in terms of their bulk pressure, we elaborate that the most useful theoretical route to this quantity is via the density profile at a flat wall. This is corroborated by extending the study to curved surfaces and establishing a connection to the particle adsorption and integrated surface excess pressure (surface tension). In the ideal-gas limit, the effect of curvature on the mechanical properties can be calculated analytically in the passive system with effective interactions and shows good (but not exact) agreement with simulations of the active models. It turns out that even the linear correction to the pressure is model specific and equals the planar adsorption in each case, which means that a known equilibrium sum rule can be extended to a regime at small but nonzero activity. In turn, the relation between the planar adsorption and the surface tension is reminiscent of the Gibbs adsorption theorem at an effective temperature. At finite densities, where particle interactions play a role, the presented effective-potential approximation captures the effect of density on the dependence of the pressure on curvature.
我们研究了活性粒子在曲面上的压力及其与其他界面性质的关系。我们既使用了活性系统的直接模拟，也使用了具有有效（对）相互作用的平衡系统的模拟，这些相互作用旨在捕捉活性的影响。通过比较活性系统和有效被动系统的体压力，我们阐述了获得该量的最有用的理论途径是通过平壁处的密度分布。将研究扩展到曲面并建立与粒子吸附和积分表面过剩压力（表面张力）的联系，证实了这一点。在理想气体极限下，对于具有有效相互作用的被动系统，可以通过解析计算曲率对力学性质的影响，并且与活性模型的模拟结果显示出良好（但不精确）的一致性。结果表明，即使是压力的线性修正也是模型特定的，并且在每种情况下都等于平面吸附，这意味着一个已知的平衡求和规则可以扩展到小但非零活性的区域。反过来，平面吸附与表面张力之间的关系让人想起有效温度下的吉布斯吸附定理。在有限密度下，粒子相互作用起作用，所提出的有效势近似捕捉了密度对压力与曲率关系的影响。
