Abstract: Nanopores are prevalent within various clay morphologies, and water flow in clay nanopores is significant for various engineering applications. In this study, we performed non-equilibrium molecular dynamics (NEMD) simulations to reveal the molecular force mechanisms of water flow in clay nanopores. The water dynamic viscosity, slip length, and average flow velocity were obtained to verify the NEMD models. Since the water confined in the nanopores maintained a dynamic mechanical equilibrium state, each water lamina can be regarded as a simply supported beam. The applied driving force, the force from clay crystal layers, the force from compensating sodium ions, and the force from other water laminae were further calculated to investigate the force mechanisms. The van der Waals barrier above the surface and hydraulic gradient lead to distribution differences in water oxygen atoms, which contribute to a net van der Waals resistance component of the force from clay crystal layers. Meanwhile, the water molecules tend to rotate to generate the electrostatic resistance component of the force from clay crystal layers and balance the increasing hydraulic gradient. Due to the velocity difference, the water molecules in the slower lamina have a higher tendency to lag and generate a net electrostatic resistance force as well as a net van der Waals driving force on the water molecules in the faster lamina, which together make up the viscous force.

黏土纳米孔内流动的分子力机制

[1]AhmedHR, AbduljauwadSN, 2017. Nano-level constitutive model for expansive clays. Géotechnique, 67(3):187-207.

[2]AlexiadisA, KassinosS, 2008. The density of water in carbon nanotubes. Chemical Engineering Science, 63(8):‍2047-2056.

[3]AllenMP, TildesleyDJ, 2017. Computer Simulation of Liquids. 2nd Edition. Oxford University Press, Oxford, UK.

[4]BerendsenHJC, PostmaJPM, van GunsterenWF, et al., 1981. Interaction models for water in relation to protein hydration. In: Pullman B (Ed.), Intermolecular Forces. Springer, Dordrecht, the Netherlands, p.331-342.

[5]BoţanA, RotenbergB, MarryV, et al., 2011. Hydrodynamics in clay nanopores. The Journal of Physical Chemistry C, 115(32):16109-16115.

[6]CaoGX, 2017. Computational simulations of pressure-driven nanofluidic behavior. SCIENTIA SINICA Physica, Mechanica & Astronomica, 47(7):070011.

[7]ChenSJ, ChenWQ, OuyangYB, et al., 2019. Transitions between nanomechanical and continuum mechanical contacts: new insights from liquid structure. Nanoscale, 11(47):22954-22963.

[8]CyganRT, LiangJJ, KalinichevAG, 2004. Molecular models of hydroxide, oxyhydroxide, and clay phases and the development of a general force field. The Journal of Physical Chemistry B, 108(4):1255-1266.

[9]DaivisPJ, ToddBD, 2018. Challenges in nanofluidics—beyond Navier‍–‍Stokes at the molecular scale. Processes, 6(9):144.

[10]HanasakiI, NakataniA, 2006a. Flow structure of water in carbon nantubes: Poiseuille type or plug-like? Journal of Chemical Physics, 124(14):144708.

[11]HanasakiI, NakataniA, 2006b. Fluidized piston model for molecular dynamics simulations of hydrodynamic flow. Modelling and Simulation in Materials Science and Engineering, 14(5):S9-S20.

[12]HansenJS, ToddBD, DaivisPJ, 2011. Prediction of fluid velocity slip at solid surfaces. Physical Review E, 84(1):016313.

[13]HessB, 2002. Determining the shear viscosity of model liquids from molecular dynamics simulations. The Journal of Chemical Physics, 116(1):209-217.

[14]HooverWG, HooverCG, 2005. Nonequilibrium molecular dynamics. Condensed Matter Physics, 8(2):247-260.

[15]KannamSK, ToddBD, HansenJS, et al., 2013. How fast does water flow in carbon nanotubes? The Journal of Chemical Physics, 138(9):094701.

[16]KondratyukN, 2019. Contributions of force field interaction forms to Green-Kubo viscosity integral in n-alkane case. The Journal of Chemical Physics, 151(7):074502.

[17]KumarR, SchmidtJR, SkinnerJL, 2007. Hydrogen bonding definitions and dynamics in liquid water. The Journal of Chemical Physics, 126(20):204107.

[18]LiJ, LiaoD, YipS, 1998. Coupling continuum to molecular-dynamics simulation: reflecting particle method and the field estimator. Physical Review E, 57(6):7259-7267.

[19]LiYC, ChenGN, ChenYM, et al., 2017. Design charts for contaminant transport through slurry trench cutoff walls. Journal of Environmental Engineering, 143(9):06017005.

[20]LiuB, QiC, ZhaoXB, et al., 2018. Nanoscale two-phase flow of methane and water in shale inorganic matrix. The Journal of Physical Chemistry C, 122(46):26671-26679.

[21]LoewensteinW, 1954. The distribution of aluminum in the tetrahedra of silicates and aluminates. American Mineralogist, 39(1-2):92-96.

[22]MarryV, RotenbergB, TurqP, 2008. Structure and dynamics of water at a clay surface from molecular dynamics simulation. Physical Chemistry Chemical Physics, 10(32):4802-4813.

[23]MartynaGJ, TobiasDJ, KleinML, 1994. Constant pressure molecular dynamics algorithms. The Journal of Chemical Physics, 101(5):4177-4189.

[24]MitchellJK, SogaK, 2005. Fundamentals of Soil Behavior. 3rd Edition. Wiley, Hoboken, USA.

[25]PlimptonS, 1995. Fast parallel algorithms for short-range molecular dynamics. Journal of Computational Physics, 117(1):1-19.

[26]QuirkJP, AylmoreLAG, 1971. Domains and quasi-crystalline regions in clay systems. Soil Science Society of America Journal, 35(4):652-654.

[27]Ramos-AlvaradoB, KumarS, PetersonGP, 2016. Hydrodynamic slip in silicon nanochannels. Physical Review E, 93(3):033117.

[28]RyckaertJP, CiccottiG, BerendsenHJC, 1977. Numerical integration of the Cartesian equations of motion of a system with constraints: molecular dynamics of n-alkanes. Journal of Computational Physics, 23(3):327-341.

[29]SamA, HartkampR, Kumar KannamS, et al., 2021. Fast transport of water in carbon nanotubes: a review of current accomplishments and challenges. Molecular Simulation, 47(10-11):905-924.

[30]SimonninP, MarryV, NoetingerB, et al., 2018. Mineral- and ion-specific effects at clay‍–‍water interfaces: structure, diffusion, and hydrodynamics. The Journal of Physical Chemistry C, 122(32):18484-18492.

[31]SkipperNT, ChangFRC, SpositoG, 1995. Monte Carlo simulation of interlayer molecular structure in swelling clay minerals. 1. Methodology. Clays and Clay Minerals, 43(3):285-293.

[32]SmithDE, 1998. Molecular computer simulations of the swelling properties and interlayer structure of cesium montmorillonite. Langmuir, 14(20):5959-5967. https:/doi.org/10.1021/la980015z

[33]StukowskiA, 2010. Visualization and analysis of atomistic simulation data with OVITO‍–‍the Open Visualization Tool. Modelling and Simulation in Materials Science and Engineering, 18(1):015012.

[34]WangL, DumontRS, DicksonJM, 2012. Nonequilibrium molecular dynamics simulation of water transport through carbon nanotube membranes at low pressure. Journal of Chemical Physics, 137(4):044102.

[35]WasakA, AkkutluIY, 2015. Permeability of organic-rich shale. SPE Journal, 20(6):1384-1396.

[36]WeiSJ, LiYC, ShenP, et al., 2023. Molecular forces of water flow in clay nanopores. The 9th International Congress on Environmental Geotechnics, p.259-268.

[37]XiongH, DevegowdaD, HuangL, 2020. Oil-water transport in clay-hosted nanopores: effects of long range electrostatic forces. AIChE Journal, 66(8):1-23.

[38]YinYM, ZhaoLL, 2020. Effects of salt concentrations and pore surface structure on the water flow through rock nanopores. Acta Physica Sinica, 69(5):054701 (in Chinese).

[39]ZhanSY, SuYL, JinZH, et al., 2020. Molecular insight into the boundary conditions of water flow in clay nanopores. Journal of Molecular Liquids, 311:113292.

[40]ZhuKQ, XuCX, 2009. Viscous Fluid Mechanics. Higher Education Press, Beijing, China(in Chinese).