@article{an_addington_long_rotnicki_sliwinska-bartkowiak_thommes_gubbins_2023, title={The Nanoscale Wetting Parameter and Its Role in Interfacial Phenomena: Phase Transitions in Nanopores}, volume={39}, ISSN={["1520-5827"]}, DOI={10.1021/acs.langmuir.3c01925}, abstractNote={Through analysis of the statistical mechanical equations for a thin adsorbed film (gas, liquid, or solid) on a solid substrate or confined within a pore, it is possible to express the equilibrium thermodynamic properties of the film as a function of just two dimensionless parameters: a nanoscale wetting parameter, αw, and pore width, H*. The wetting parameter, αw, is defined in terms of molecular parameters for the adsorbed film and substrate and so is applicable at the nanoscale and for films of any phase. The main assumptions in the treatment are that (a) the substrate structure is not significantly affected by the adsorbed layer and (b) the diameter of the adsorbate molecules is not very small compared to the spacing of atoms in the solid substrate. We show that different surface geometries of the substrate (e.g., slit, cylindrical, and spherical pores) and various models of wall heterogeneity can be accounted for through a well-defined correction to the wetting parameter; no new dimensionless variables are introduced. Experimental measurements are reported for contact angles for various liquids on several planar substrates and are shown to be closely correlated with the nanoscale wetting parameter. We apply this approach to phase separation in nanopores of various geometries. Molecular simulation results for the phase diagram in confinement, obtained by the flat histogram Monte Carlo method, are reported and are shown to be closely similar to experimental results for capillary condensation, melting, and the triple point. The value of the wetting parameter, αw, is shown to determine the qualitative behavior (e.g., increase vs decrease in the melting temperature, capillary condensation vs evaporation), whereas the pore width determines the magnitude of the confinement effect. The triple point temperature and pressure for the confined phase are always lower than those for the bulk phase for all cases studied.}, number={51}, journal={LANGMUIR}, author={An, Rong and Addington, Cody K. and Long, Yun and Rotnicki, Konrad and Sliwinska-Bartkowiak, Malgorzata and Thommes, Matthias and Gubbins, Keith E.}, year={2023}, month={Dec}, pages={18730–18745} }
 @article{long_palmer_coasne_shi_sliwinska-bartkowiak_gubbins_2020, title={Reply to the 'Comment on "Pressure enhancement in carbon nanopores: a major confinement effect"' by D. van Dijk, Phys. Chem. Chem. Phys., 2020, 22, DOI: 10.1039/C9CP02890K}, volume={22}, ISSN={["1463-9084"]}, DOI={10.1039/c9cp04289j}, abstractNote={By calculating the unique effective tangential pressure and discussing recent evidence from experiment and simulations, we show that the high pressure and strong compression in adsorbed layers for wetting systems on carbon are significant.}, number={17}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Long, Yun and Palmer, Jeremy C. and Coasne, Benoit and Shi, Kaihang and Sliwinska-Bartkowiak, Malgorzata and Gubbins, Keith E.}, year={2020}, month={May}, pages={9826–9830} }
 @article{addington_long_gubbins_2018, title={The pressure in interfaces having cylindrical geometry}, volume={149}, ISSN={0021-9606 1089-7690}, url={http://dx.doi.org/10.1063/1.5037054}, DOI={10.1063/1.5037054}, abstractNote={While much work has been reported on the statistical mechanics and molecular simulation of interfaces of planar and spherical geometries, very little has been published on the interfaces of cylindrical geometry. The cylindrical geometry is important for the study of cylindrical micelles and particularly for nano-phases confined within cylindrical pores since the most well-defined porous materials (e.g., carbon and silicon nanotubes, SBA-15 and KIT-6 silicas) that are presently available are of this geometry. In this work, we derive the statistical mechanical equations for the pressure tensor for an interfacial region of cylindrical geometry via the virial route and for the condition of mechanical (hydrostatic) equilibrium. We also report the equation for the surface tension via the mechanical route. Monte Carlo and molecular dynamics simulation results are obtained for two example systems involving a fluid nano-phase of Lennard-Jones argon: a gas-liquid interface of cylindrical geometry and a confined nano-phase within a cylindrical carbon pore. All three diagonal elements of the pressure tensor are reported in each case, the component normal to the interface, PN = Pρρ, and the two tangential components PTϕ = Pϕϕ and PTz = Pzz, where (ρ, z, ϕ) are the usual cylindrical polar coordinates. For the cylindrical pore, the tangential pressures, Pϕϕ and Pzz, show strong compression in the adsorbed layers, as has been found in slit-shaped and spherical pores.}, number={8}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Addington, Cody K. and Long, Yun and Gubbins, Keith E.}, year={2018}, month={Aug}, pages={084109} }
 @article{coasne_long_gubbins_2014, title={Pressure effects in confined nanophases}, volume={40}, ISSN={["1029-0435"]}, DOI={10.1080/08927022.2013.829227}, abstractNote={In this article, we review how pressure effects in pores affect both the physics of the confined fluid and the properties of the host porous material. Molecular simulations in which high-pressure effects were observed are first discussed; we will see how the strong dependence on bulk phase pressure of the freezing temperature of a fluid confined in nanopores can be explained by important variations of the pressure within the pore. We then discuss recent works in which direct calculations of the pressure tensor of fluids confined in pores provide evidence for large pressure enhancements. Finally, practical applications of these pressure effects in which gas adsorption in microporous solids (pore size < 2 nm) was found to enhance their mechanical properties by increasing the elastic modulus by a factor 4 are discussed.}, number={7-9}, journal={MOLECULAR SIMULATION}, author={Coasne, B. and Long, Y. and Gubbins, K. E.}, year={2014}, month={Aug}, pages={721–730} }
 @article{long_śliwińska-bartkowiak_drozdowski_kempiński_phillips_palmer_gubbins_2013, title={High pressure effect in nanoporous carbon materials: Effects of pore geometry}, volume={437}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2012.11.024}, DOI={10.1016/j.colsurfa.2012.11.024}, abstractNote={Abundant experimental evidence suggests that adsorbates confined in nanoporous materials exhibit high pressures, such as high pressure crystal structures, high pressure chemical reactions, and the deformation of pore walls due to the adsorbate. We report molecular simulation studies of the pressure tensor for simple adsorbates (e.g. argon) in carbon nanopores of slit, cylindrical and spherical geometries. We find that for modest bulk phase pressures of 1 bar or less, the pressures parallel to the pore walls (tangential pressure) is of the order 104–105 bar, while the pressure normal to the wall is of the order of 103 bar, and can be positive or negative depending on the pore size. Moreover, we find that the pore geometry has a large effect on the structure of the adsorbate and thus on the in-pore pressure because of the curvature that determines the strength of the adsorbate–wall interaction. For the same pore size, temperature and bulk pressure, the in-pore tangential pressure is the largest in spherical pores, followed by that in cylindrical pores and slit pores. We also study the normal pressure of carbon tetrachloride and water confined in activated carbon fibers by molecular simulations and experiments. The pressure acting on the pore wall is found to be of the order of several thousand bar by both methods. Experiments also find that the pore can be expanded or contracted, depending on pore width, as we predict by molecular simulation.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Long, Yun and Śliwińska-Bartkowiak, Małgorzata and Drozdowski, Henryk and Kempiński, Mateusz and Phillips, Katherine A. and Palmer, Jeremy C. and Gubbins, Keith E.}, year={2013}, month={Nov}, pages={33–41} }
 @article{long_palmer_coasne_sliwinska-bartkowiak_jackson_mueller_gubbins_2013, title={On the molecular origin of high-pressure effects in nanoconfinement: The role of surface chemistry and roughness}, volume={139}, ISSN={0021-9606 1089-7690}, url={http://dx.doi.org/10.1063/1.4824125}, DOI={10.1063/1.4824125}, abstractNote={Experiments and simulations both suggest that the pressure experienced by an adsorbed phase confined within a carbon nanoporous material can be several orders of magnitude larger than the bulk phase pressure in equilibrium with the system. To investigate this pressure enhancement, we report a molecular-simulation study of the pressure tensor of argon confined in slit-shaped nanopores with walls of various models, including carbon and silica materials. We show that the pressure is strongly enhanced by confinement, arising from the effect of strongly attractive wall forces; confinement within purely repulsive walls does not lead to such enhanced pressures. Simulations with both the Lennard-Jones and Barker-Fisher-Watts intermolecular potentials for argon-argon interactions give rise to similar results. We also show that an increase in the wall roughness significantly decreases the in-pore pressure due to its influence on the structure of the adsorbate. Finally, we demonstrate that the pressures calculated from the mechanical (direct pressure tensor calculations) and the thermodynamic (volume perturbation method) routes yield almost identical results, suggesting that both methods can be used to calculate the local pressure tensor components in the case of these planar geometries.}, number={14}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Long, Yun and Palmer, Jeremy C. and Coasne, Benoit and Sliwinska-Bartkowiak, Malgorzata and Jackson, George and Mueller, Erich A. and Gubbins, Keith E.}, year={2013}, month={Oct}, pages={144701} }
 @article{śliwińska-bartkowiak_drozdowski_kempiński_jażdżewska_long_palmer_gubbins_2012, title={Structural analysis of water and carbon tetrachloride adsorbed in activated carbon fibres}, volume={14}, ISSN={1463-9076 1463-9084}, url={http://dx.doi.org/10.1039/C2CP22111J}, DOI={10.1039/c2cp22111j}, abstractNote={We report X-ray diffraction studies of water and carbon tetrachloride adsorbed in nanoporous activated carbon fibres. The fibres are built of turbostratic nanoparticles separated by quasi two-dimensional voids, forming narrow slit-shaped pores. In order to determine the structure of water within the pores and its influence on the fibres' structure, mean interatomic and intermolecular distances have been estimated from the positions of the maxima of the normalized angular distribution functions obtained by X-ray diffraction. We observe a cluster arrangement of the water molecules, as well as significant changes in the interlayer distance of the carbon nanoparticles upon adsorption of both water and carbon tetrachloride. The results suggest that very high pressures arise within the pores, as has been observed in molecular simulations, and this may give rise to the large change in electronic properties of the fibres after adsorption of guest molecules. The in-pore pressure normal to the pore walls is estimated from the experimental data, and is found to be positive and of the order 4000 bar. Molecular simulation results for the normal pressure component are presented for both water and carbon tetrachloride in carbon slit pores, and are in general agreement with the experiments. For both fluids the normal pressure is an oscillating function of pore width.}, number={19}, journal={Physical Chemistry Chemical Physics}, publisher={Royal Society of Chemistry (RSC)}, author={Śliwińska-Bartkowiak, Małgorzata and Drozdowski, Henryk and Kempiński, Mateusz and Jażdżewska, Monika and Long, Yun and Palmer, Jeremy C. and Gubbins, Keith E.}, year={2012}, pages={7145} }
 @article{long_palmer_coasne_sliwinska-bartkowiak_gubbins_2012, title={Under pressure: Quasi-high pressure effects in nanopores}, volume={154}, ISSN={["1873-3093"]}, DOI={10.1016/j.micromeso.2011.07.017}, abstractNote={Phenomena that occur only at high pressures in bulk phases are often observed in nanopores, suggesting that the pressure in such confined phases is large. We develop two models to study the pressure tensor of an argon nanophase confined in carbon micropores by molecular simulation, and show that the in-pore tangential pressure is positive and on the order of 104 bar, while the normal pressure can be positive or negative depending on pore width, with a magnitude of ∼103 bar at ambient bulk pressure. We find that the in-pore tangential pressure is very sensitive to the bulk pressure, suggesting that it should be possible to control the former over wide ranges in laboratory experiments. We also report results for porous materials other than carbon, and show that the pressure enhancement is smaller for pores with weakly attractive walls (e.g. silica and oxides), but larger for more strongly attractive walls (e.g. mica).}, journal={MICROPOROUS AND MESOPOROUS MATERIALS}, author={Long, Yun and Palmer, Jeremy C. and Coasne, Benoit and Sliwinska-Bartkowiak, Malgorzata and Gubbins, Keith E.}, year={2012}, month={May}, pages={19–23} }
 @article{long_palmer_coasne_sliwinska-bartkowiak_gubbins_2011, title={Pressure enhancement in carbon nanopores: a major confinement effect}, volume={13}, ISSN={["1463-9084"]}, DOI={10.1039/c1cp21407a}, abstractNote={Phenomena that only occur at high pressures in bulk phases are observed in nanopores because of a pressure enhancement effect.}, number={38}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Long, Yun and Palmer, Jeremy C. and Coasne, Benoit and Sliwinska-Bartkowiak, Malgorzata and Gubbins, Keith E.}, year={2011}, pages={17163–17170} }