@article{lisal_cosoli_smith_jain_gubbins_2008, title={Molecular-level simulations of chemical reaction equilibrium for nitric oxide dimerization reaction in disordered nanoporous carbons}, volume={272}, ISSN={["0378-3812"]}, DOI={10.1016/j.fluid.2008.07.015}, abstractNote={We report a molecular-level simulation study of the effects of confinement on chemical reaction equilibrium for the NO dimerization reaction, 2NO ⇌ (NO)2, in disordered nanoporous carbons. We use the Reaction Ensemble Monte Carlo (RxMC) method [W.R. Smith, B. Tříska, J. Chem. Phys. 100 (1994) 3019–3027; J.K. Johnson, A.Z. Panagiotopoulos, K.E. Gubbins, Mol. Phys. 81 (1994) 717–733] to investigate the effects of temperature and bulk pressure on the reaction conversion in three models of disordered nanoporous carbons obtained from sucrose in equilibrium with a vapor reservoir. Atomistic models of the carbons used [S.K. Jain, R.J.-M. Pellenq, J.P. Pikunic, K.E. Gubbins, Langmuir 22 (2006) 9942–9948] were constructed using the Hybrid Reverse Monte Carlo method, differing by the processing conditions used in the preparation of the corresponding real material. In addition to the RxMC simulations, we test conventional macroscopic adsorption models, such as the Langmuir–Freundlich, multisite Langmuir, vacancy solution and ideal adsorption solution models, in connection with the ideal-gas model for the vapor reservoir to model the reaction equilibrium. Pure fluid adsorption isotherms needed as input to the macroscopic models for mixture adsorption are generated using the Gibbs Ensemble Monte Carlo or Grand Canonical Monte Carlo simulations. We analyze the effects of the confinement, temperature and bulk pressure on the NO dimerization reaction equilibrium in terms of the reactive adsorption isotherms. The RxMC simulations and thermodynamic modeling show that the sucrose-based carbons substantially increase the conversion of NO to (NO)2 with respect to the vapor reservoir, where the conversion is less than a few percent.}, number={1-2}, journal={FLUID PHASE EQUILIBRIA}, author={Lisal, Martin and Cosoli, Paolo and Smith, William R. and Jain, Surendra K. and Gubbins, Keith E.}, year={2008}, month={Oct}, pages={18–31} }
 @article{coasne_jain_gubbins_2007, title={Adsorption and dynamics of argon in porous carbons}, volume={141}, DOI={10.1141/epjst/e2007-00022-2}, journal={European Physical Journal. Special Topics}, author={Coasne, B. and Jain, S. K. and Gubbins, Keith}, year={2007}, pages={121–125} }
 @article{coasne_jain_naamar_gubbins_2007, title={Freezing of argon in ordered and disordered porous carbon}, volume={76}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.76.085416}, abstractNote={We report a molecular simulation study on the freezing of argon within two models of activated porous carbons. Model A is a regular slit-shaped nanopore, which represents an ordered graphitic porous carbon with a single pore width. Model B is a realistic sample of a disordered porous carbon obtained from reverse Monte Carlo. The morphological pore shape and topological pore connectivity disorders of model B represent in a realistic way the complex porous structure of materials obtained after carbonization and activation of pure saccharose. This study is aimed at estimating how the effect of disorder of the porous material affects freezing and melting of simple adsorbates. Freezing of argon in the slit pore model conforms to the classical behavior for an adsorbate confined in a strongly attractive pore; the in-pore freezing temperature is higher than that of the bulk fluid, and the shift in freezing temperature increases with decreasing pore size. It is found that the two-dimensional crystal layers of argon within the slit pores have a hexagonal structure i.e., triangular symmetry. Freezing of argon within model B strongly departs from that observed for model A. No crystallization is observed for argon in the complex porosity of model B. Nevertheless the confined phase undergoes structural changes at a temperature T=115 K; this temperature is close to the freezing temperature found for the slit pore with width H=1.1 nm, which corresponds to the mean pore size in model B. For temperatures larger than T =115 K, the confined phase in model B exhibits a liquid-like behavior as revealed from pair correlation functions and bond-order parameters. On the other hand, the confined phase for T115 K has more shortrange order than the liquid phase but its overall behavior remains liquid-like. Our results indicate that the changes observed at T115 K are due 1 to the appearance in the confined phase of a small amount of crystal atoms and 2 to the fact that the fraction of liquid-like atoms having at least seven nearest neighbors reaches a plateau value of 80%. The results provide a basis for the interpretation of experiments such as NMR and scattering experiments on freezing in disordered porous materials.}, number={8}, journal={PHYSICAL REVIEW B}, author={Coasne, Benoit and Jain, Surendra K. and Naamar, Linda and Gubbins, Keith E.}, year={2007}, month={Aug} }
 @article{jain_gubbins_2007, title={Ring connectivity: Measuring network connectivity in network covalent solids}, volume={23}, ISSN={["0743-7463"]}, DOI={10.1021/la0534017}, abstractNote={In atomistic models of amorphous materials, ring statistics provide a measure of medium-range order. However, while ring statistics tell us the number of rings present in the model, they do not give us any information about the arrangement of rings, e.g., whether the rings are clustered and how big the cluster is. In this work we present a method to calculate the ring connectivity, or clustering, of rings. We first calculate the rings present in the model using the shortest path criteria of Franzblau and then find the rings that are connected together and group them into clusters. We apply our method to a set of models of disordered carbons, obtained using a reverse Monte Carlo procedure developed in a recent work. We found that in these carbon models the five-, six-, and seven-membered rings are connected together, forming clusters. After isolating the clusters, we found that they resemble defective graphene segments twisted in a complex way. The clusters give further insight about the arrangement of carbon atoms in microporous carbons at a larger length scale. Moreover, the method can be applied to any network covalent solid that contains rings and thus gives information about the ring connectivity present in such materials.}, number={3}, journal={LANGMUIR}, author={Jain, Surendra K. and Gubbins, Keith E.}, year={2007}, month={Jan}, pages={1123–1130} }
 @article{coasne_gubbins_hung_jain_2006, title={Adsorption and structure of argon in activated porous carbons}, volume={32}, ISSN={["1029-0435"]}, DOI={10.1080/08927020600675707}, abstractNote={Molecular simulations are used to investigate the adsorption and structure of argon in ordered and disordered models of porous carbons. The ordered porous carbon (model A) is an assembly of regular slit pores of different sizes, while the disordered porous carbon (model B) is a structural model that reproduces the complex pore shape and pore connectivity of saccharose-based porous carbons. The same pore size distribution is used for models A and B so that we are able to estimate, for similar confinement effects, how the disorder of the porous material affects the adsorption and structure of the confined fluid. Adsorption of argon at 77.4 K in the two models is studied using Grand Canonical Monte Carlo simulations. The structure of the confined fluid is analyzed using crystalline bond order parameters and positional or bond orientational pair correlation functions. The filling pressure for the assembly of slit pores is much lower than that for the disordered porous carbon. It is also found that the isosteric heat of adsorption for the ordered porous model overestimates that for the disordered porous model. The results suggest that the agreement between models A and B would be improved if the same density of carbon atoms were used in these two models. Strong layering of Ar is observed at all pressures for model A. The confined phase is composed of liquid-like layers at low-pressures, which crystallize into well-defined hexagonal 2D crystals after complete filling of the pores. The structure of argon in the disordered porous carbon strongly departs from that in the slit pore model. Although its structure remains liquid-like overall, argon confined in model B is composed of both crystalline clusters and amorphous (solid or liquid) nano-domains.}, number={7}, journal={MOLECULAR SIMULATION}, author={Coasne, Benoit and Gubbins, Keith E. and Hung, Francisco R. and Jain, Surendra K.}, year={2006}, month={Jun}, pages={557–566} }
 @article{coasne_jain_gubbins_2006, title={Adsorption, structure and dynamics of fluids in ordered and disordered models of porous carbons}, volume={104}, ISSN={["1362-3028"]}, DOI={10.1080/00268970601012736}, abstractNote={Grand Canonical Monte Carlo and Molecular Dynamics simulations are used to investigate the adsorption and dynamics of argon in ordered and disordered models of porous carbons. The ordered porous carbon (model A) is a regular slit pore made up of graphene sheets. The disordered porous carbon (model B) is a structural model that reproduces the morphological (pore shape) and topological (pore connectivity) disorders of saccharose-based porous carbons. Three pore widths, H = 7, 11, and 15 Å, are selected for model A; they correspond to the smaller, mean, and larger pore sizes of model B. The filling pressures for the graphite slit pores are lower than those for the disordered porous carbon. It is also found that model A is not able to capture the behaviour of the isosteric heat of adsorption of model B. For all pressures, the confined phase in model A is composed of well-defined layers, which crystallize into hexagonal 2D crystals after complete filling of the pores. In contrast, the structure of argon in the disordered porous carbon remains liquid-like overall. It is also found that the slit pore model cannot reproduce the dynamics of argon in the disordered porous carbon. While the self-diffusivity of argon in model A decreases with increasing loading, it exhibits a maximum for model B. Such a non-monotonic behaviour of the self-diffusivity for the disordered porous carbon can be explained by the surface (energetic) heterogeneities of the material.}, number={22-24}, journal={MOLECULAR PHYSICS}, author={Coasne, B. and Jain, S. K. and Gubbins, K. E.}, year={2006}, pages={3491–3499} }
 @article{coasne_jain_gubbins_2006, title={Freezing of fluids confined in a disordered nanoporous structure}, volume={97}, number={10}, journal={Physical Review Letters}, author={Coasne, B. and Jain, S. K. and Gubbins, K. E.}, year={2006} }
 @article{jain_pellenq_pikunic_gubbins_2006, title={Molecular modeling of porous carbons using the hybrid reverse Monte Carlo method}, volume={22}, ISSN={["0743-7463"]}, DOI={10.1021/la053402z}, abstractNote={We apply a simulation protocol based on the reverse Monte Carlo (RMC) method, which incorporates an energy constraint, to model porous carbons. This method is called hybrid reverse Monte Carlo (HRMC), since it combines the features of the Monte Carlo and reverse Monte Carlo methods. The use of the energy constraint term helps alleviate the problem of the presence of unrealistic features (such as three- and four-membered carbon rings), reported in previous RMC studies of carbons, and also correctly describes the local environment of carbon atoms. The HRMC protocol is used to develop molecular models of saccharose-based porous carbons in which hydrogen atoms are taken into account explicitly in addition to the carbon atoms. We find that the model reproduces the experimental pair correlation function with good accuracy. The local structure differs from that obtained with a previous model (Pikunic, J.; Clinard, C.; Cohaut, N.; Gubbins, K. E.; Guet, J. M.; Pellenq, R. J.-M.; Rannou, I.; Rouzaud, J. N. Langmuir 2003, 19 (20), 8565). We study the local structure by calculating the nearest neighbor distribution, bond angle distribution, and ring statistics.}, number={24}, journal={LANGMUIR}, author={Jain, Surendra K. and Pellenq, Roland J. -M. and Pikunic, Jorge P. and Gubbins, Keith E.}, year={2006}, month={Nov}, pages={9942–9948} }
 @inproceedings{jain_fuhr_pellenq_pikunic_bichara_gubbins_2006, title={Stability of porous carbon structures obtained from reverse Monte Carlo using tight binding and bond order Hamiltonians}, volume={160}, DOI={10.1016/s0167-2991(07)80023-1}, abstractNote={The constrained Reverse Monte-Carlo (RMC) technique [1,2] was used to generate atomic configurations of disordered microporous carbons in a previous work. However, a carbon structure obtained from RMC is a result of the fitting to some structural data such as obtained from X-ray diffraction; it does not guarantee the stability of the resulting models when a realistic interatomic potential is used. In the present work, we studied the stability of these RMC structures using canonical Monte-Carlo simulations. Two different descriptions of the carbon-carbon and carbon-hydrogen interactions are used, both encompassing the bonding processes characteristic of carbon chemistry. The first approach is based on a bond-order potential while the second considers a tight binding model. We found that the structures obtained from RMC simulations undergo local structural changes upon relaxation, however the porous structure of the models remains intact.}, booktitle={Characterization of porous solids vii - proceedings of the 7th international symposium on the characterization of porous solids (cops-vii), aix-en-provence, france, 26-28 may 2005}, author={Jain, S. K. and Fuhr, J. and Pellenq, R. J. M. and Pikunic, J. P. and Bichara, C. and Gubbins, Keith}, year={2006}, pages={169–176} }
 @article{nguyen_bhatia_jain_gubbins_2006, title={Structure of saccharose-based carbon and transport of confined fluids: hybrid reverse Monte Carlo reconstruction and simulation studies}, volume={32}, ISSN={["1029-0435"]}, DOI={10.1080/08927020600675699}, abstractNote={We present results of the reconstruction of a saccharose-based activated carbon (CS1000a) using hybrid reverse Monte Carlo (HRMC) simulation, recently proposed by Opletal et al. [1]. Interaction between carbon atoms in the simulation is modeled by an environment dependent interaction potential (EDIP) [2,3]. The reconstructed structure shows predominance of sp2 over sp3 bonding, while a significant proportion of sp hybrid bonding is also observed. We also calculated a ring distribution and geometrical pore size distribution of the model developed. The latter is compared with that obtained from argon adsorption at 87 K using our recently proposed characterization procedure [4], the finite wall thickness (FWT) model. Further, we determine self-diffusivities of argon and nitrogen in the constructed carbon as functions of loading. It is found that while there is a maximum in the diffusivity with respect to loading, as previously observed by Pikunic et al. [5], diffusivities in the present work are 10 times larger than those obtained in the prior work, consistent with the larger pore size as well as higher porosity of the activated saccharose carbon studied here.}, number={7}, journal={MOLECULAR SIMULATION}, author={Nguyen, T. X. and Bhatia, S. K. and Jain, S. K. and Gubbins, K. E.}, year={2006}, month={Jun}, pages={567–577} }
 @article{jain_pikunic_pellenq_gubbins_2005, title={Effects of activation on the structure and adsorption properties of a nanoporous carbon using molecular simulation}, volume={11}, ISSN={["0929-5607"]}, DOI={10.1007/s10450-005-5950-3}, number={Suppl.1}, journal={ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY}, author={Jain, SK and Pikunic, JP and Pellenq, RJM and Gubbins, KE}, year={2005}, pages={355–360} }