Patel Rohan, Addula Ravi Kumar Reddy, Shaik Majeed, Punnathanam Sudeep N
Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India.
Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Chem Phys. 2022 Oct 7;157(13):134705. doi: 10.1063/5.0101013.
Wettability of rock surfaces with respect to oil and water, which is characterized by the contact angle, is an important factor that determines the efficacy of enhanced oil recovery operations. Experimental determination of contact angles for oil-water-rock systems is expensive and time-consuming due to the extremely long times needed for the establishment of adsorption equilibrium at the liquid-solid interface. Hence, molecular simulations form an attractive tool for computing contact angles. In this work, we use the cleaving wall technique that was developed previously in our group [R. K. R. Addula and S. N. Punnathanam, J. Chem. Phys. 153, 154504 (2020)] to compute solid-liquid interfacial free energy, which is then combined with Young's equation to compute the oil-water contact angle on silica surfaces. The silica surface is modeled with the INTERFACE force field that has been developed to accurately reproduce experimental data. We have considered three different surface chemistries of silica, namely, Q, Q, and Q, in this study. Our calculations reveal that while the Q and Q surfaces are completely wetted by water, the Q surface is partially non-wetted by water. All the simulations needed for this calculation can be performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) molecular package. This should facilitate wider adoption of the Young's equation route to compute contact angles for systems comprised of complex molecules.
岩石表面对油和水的润湿性以接触角为特征，是决定强化采油作业效果的一个重要因素。由于在液 - 固界面建立吸附平衡所需时间极长，油水 - 岩石系统接触角的实验测定既昂贵又耗时。因此，分子模拟成为计算接触角的一种有吸引力的工具。在这项工作中，我们使用我们小组之前开发的劈裂壁技术[R. K. R. Addula和S. N. Punnathanam，《化学物理杂志》153, 154504 (2020)]来计算固 - 液界面自由能，然后将其与杨氏方程相结合，以计算二氧化硅表面的油水接触角。二氧化硅表面采用已开发的用于精确再现实验数据的INTERFACE力场进行建模。在本研究中，我们考虑了二氧化硅的三种不同表面化学性质，即Q、Q和Q。我们的计算表明，虽然Q和Q表面被水完全润湿，但Q表面部分不被水润湿。该计算所需的所有模拟都可以使用大规模原子/分子大规模并行模拟器（LAMMPS）分子软件包来执行。这应该有助于更广泛地采用杨氏方程方法来计算由复杂分子组成的系统的接触角。
