Molecular modeling at the electronic and atomistic levels plays an important and complementary role to experimental studies of confinement effects. Theory and atomistic simulation can provide fundamental understanding, determine the limits of well known macroscopic laws such as Kelvin's equation, provide predictions for systems that are difficult to study via experiment (e.g. adsorption of highly toxic gases), and can be used to gain detailed molecular level information that may not be accessible in the laboratory (e.g. the local structure and composition of confined phases). We describe the most important and useful methods that are based firmly on quantum mechanics and statistical mechanics, including ab intio and classical density functional theories, and Monte Carlo and molecular dynamics simulation. We discuss their strengths and limitations. We then describe examples of applications of these methods to adsorption and equilibrium properties, including testing the Kelvin equation, determination of pore size distributions and capillary phenomena. Applications to self and transport diffusion, including single-file and anomalous diffusion, and viscous flow in nanoporous materials are described. The use of these methods to understand confinement effects on chemical reactions in heterogeneous media is treated, including effects on reaction equilibria, rates and mechanism. Finally we discuss the current status of molecular modeling in this area, and the outlook and future research needs for the next few years. The treatment is suitable for the general technical reader.

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Using molecular simulation, four types of nanoporous carbons are examined as adsorbents for the separation of CO(2)/CH(4) mixtures at ambient temperature and pressures up to 10 MPa. First, the adsorption selectivity of CO(2) is investigated in carbon slit pores and single-walled carbon nanotube bundles in order to find the optimal pore dimensions for CO(2) separation. Then, the adsorptive properties of the optimized slit pore and nanotube bundle are compared with two realistic nanoporous carbon models: a carbon replica of zeolite Y and an amorphous carbon. For the four carbon models, adsorption isotherms and isosteric heats of adsorption are presented for both pure components and mixtures. Special attention is given to the calculation of excess isotherms and isosteric heats, which are necessary to assess the performance of model nanoporous materials in the context of experimental measurements. From these results, we discuss the impact that variables such as pore size, pore morphology, pressure and mixture composition have on the performance of nanoporous carbons for CO(2) separation.

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A suite of computational tools is described for particle-based mesoscale simulations of the nonequilibrium dynamics of energetic solids, including mechanical deformation, phase transitions, and chemical reactivity triggered by shock or thermal loading. The method builds upon our recent advances both in generating coarse-grain models under high strains and in developing a variant of dissipative particle dynamics (DPD) that includes chemical reactions. To describe chemical reactivity, a coarse-grain particle equation-of-state was introduced into the constant-energy DPD variant that rigorously treats complex chemical reactions and the associated chemical energy release. As illustration of these developments, we present simulations of shock compression of an RDX crystal and its thermal decomposition under high temperatures. We also discuss our current efforts toward a highly scalable domain-decomposition implementation that extends applicability to micrometer-size simulations. With appropriate parametrization, the method is applicable to other materials whose dynamic response is driven by microstructural heterogeneities.