Surface-Constrained Metropolis Monte Carlo: Simulation of Reactions on Triply Periodic Minimal Surfaces.

Triply periodic minimal surfaces (TPMS) inspired by nature serve as a foundation for developing novel nanomaterials, such as templated silicas, graphene sponges, and schwarzites, with customizable optical, poroelastic, adsorptive, catalytic, and other properties. Computer simulations of reactions on TPMS using reactive intermolecular potentials hold great promise for constructing and screening potential TPMS with the desired properties. Here, we developed an off-lattice, surface-constrained Metropolis Monte Carlo (SC-MMC) algorithm that utilized a temperature quench process.

The Finite Pore Volume GAB Adsorption Isotherm Model as a Simple Tool to Estimate a Diameter of Cylindrical Nanopores.

The finite pore volume Guggenheim-Anderson-de Boer (fpv-GAB) adsorption isotherm model has been considered as a simple tool which not only enables us to analyze the shape of isotherms theoretically, but also provides information about pore diameter. The proposed methodology is based on the geometrical considerations and the division of the adsorption space into two parts: the monolayer and the multilayer space. The ratio of the volumes of these two spaces is unambiguously related to the pore diameter.

The effects of confinement in pores built of folded graphene sheets on the equilibrium of nitrogen monoxide dimerisation reaction.

In the current work we have used reactive Monte Carlo simulations to systematically study the effects of graphene folding on equilibria of NO dimerisation occurring at isolated surfaces and in porous networks built of corrugated graphene sheets. It has been demonstrated that the folding of isolated graphene sheets significantly improves the yield of reactions occurring on their surface. Then, it has also been shown that in slit-like pores formed by the folded graphene sheets the reaction yield depends on the corrugation and arrangement of the pore walls.

Carbon Nanohorns as Reaction Nanochambers - a Systematic Monte Carlo Study.

Carbon nanohorns (CNHs, one of the newest carbon allotropes) have been subjected to intensive experimental and theoretical studies due to their potential applications. One of such applications can be their use as reaction nanochambers. However, experimental studies on the reaction equilibria under confinement are extremely challenging since accurate measurements of the concentrations of reacting species in pores are a very hard task.

To what extent can mutual shifting of folded carbonaceous walls in slit-like pores affect their adsorption properties?

We have performed systematic Monte Carlo studies on the influence of shifting the walls in slit-like systems constructed from folded graphene sheets on their adsorption properties. Specifically, we have analysed the effect on the mechanism of argon adsorption (T  =  87 K) and on adsorption and separation of three binary gas mixtures: CO2/N2, CO2/CH4 and CH4/N2 (T  =  298 K). The effects of the changes in interlayer distance were also determined.

Nuclear Quantum Effects in the Layering and Diffusion of Hydrogen Isotopes in Carbon Nanotubes.

Although recent experimental studies have demonstrated that H2 and D2 molecules wet the inner surface of supergrowth carbon nanotubes at low temperatures, characterization of the structural and dynamical properties in this regime is challenging. This Letter presents a theoretical study of self-diffusion in pure and binary H2, D2, and T2 contact monolayer films formed on the inner surface of a carbon nanotube. Our results show that monolayer formation and self-diffusion both in pure hydrogen isotopes and in H2/T2 and H2/D2 isotope mixtures is impacted by nuclear quantum effects, suggesting potential applications of carbon nanotubes for the separation of hydrogen isotopes.

New insights into the ideal adsorbed solution theory.

The GCMC technique is used for simulation of adsorption of CO2-CH4, CO2-N2 and CH4-N2 mixtures (at 298 K) on six porous carbon models. Next we formulate a new condition of the IAS concept application, showing that our simulated data obey this condition. Calculated deviations between IAS predictions and simulation results increase with the rise in pressure as in the real experiment.

Influence of activated carbon porosity and surface oxygen functionalities' presence on adsorption of acetonitrile as a simple polar volatile organic compound.

Based on series of porous carbon models, systematic Monte Carlo studies on the adsorption of acetonitrile (as a simple representative of polar volatile organic compounds) were performed. The influence of porosity and chemical composition of the carbon surface on CH3CN adsorption was studied and it was shown that both the factors influenced the adsorption mechanism. A decrease in the pore size and the introduction of oxygen surface groups led to a rise in adsorption energy and to an increase in the filling of accessible volume in the low-pressure part of the isotherm.

Folding of graphene slit like pore walls--a simple method of improving CO2 separation from mixtures with CH4 or N2.

We report for the first time a detailed procedure for creating a simulation model of energetically stable, folded graphene-like pores and simulation results of CO2/CH4 and CO2/N2 separation using these structures. We show that folding of graphene structures is a very promising method to improve the separation of CO2 from mixtures with CH4 and N2. The separation properties of the analysed materials are compared with carbon nanotubes having similar diameters or S/V ratio.

Toward in silico modeling of palladium-hydrogen-carbon nanohorn nanocomposites.

We present the first in silico modeling of the Pd-H-single-walled carbon nanohorn nanocomposites. Temperature-quench Monte Carlo simulations are used to generate the most stable morphologies of Pd81 clusters (cluster sizes of ∼2 nm) deposited inside the morphologically defective single-walled carbon nanohorns (S. Furmaniak, A.

MD simulation of organics adsorption from aqueous solution in carbon slit-like pores. Foundations of the pore blocking effect.

The results of systematic studies of organics adsorption from aqueous solutions (at the neutral pH level) in a system of slit-like carbon pores having different sizes and oxygen groups located at the pore mouth are reported. Using molecular dynamics simulations (GROMACS package) the properties of adsorbent-adsorbate (benzene, phenol or paracetamol) as well as adsorbent-water systems are discussed. After the introduction of surface oxygen functionalities, adsorption of organic compounds decreases (in accordance with experimental data) and this is caused by the accumulation of water molecules at pore entrances.

To the pore and through the pore: thermodynamics and kinetics of helium in exotic cubic carbon polymorphs.

Applying pore size analysis, Monte Carlo simulations, and transition state theory, we study the molecular sieving properties of recently discovered crystalline exotic cubic carbon allotropes (Hu et al., J. Phys.

Separation of CO2-CH4 mixtures on defective single walled carbon nanohorns--tip does matter.

Using realistic models of single-walled carbon nanohorns and their single-walled carbon nanotube counterparts, we study the equilibrium separation of CO2-CH4 mixtures near ambient operating conditions by using molecular simulations. We show that regardless of the studied operating conditions (i.e.

Carbon materials as new nanovehicles in hot-melt drug deposition.

The application of commercially available carbon materials (nanotubes and porous carbons) for the preparation of drug delivery systems is studied. We used two types of carbon nanotubes (CNT) and two activated carbons as potential materials in so-called hot-melt drug deposition (HMDD). The materials were first studied using Raman spectroscopy.

Synergetic effect of carbon nanopore size and surface oxidation on CO2 capture from CO2/CH4 mixtures.

We have studied the synergetic effect of confinement (carbon nanopore size) and surface chemistry (the number of carbonyl groups) on CO2 capture from its mixtures with CH4 at typical operating conditions for industrial adsorptive separation (298 K and compressed CO2-CH4 mixtures). Although both confinement and surface oxidation have an impact on the efficiency of CO2/CH4 adsorptive separation at thermodynamics equilibrium, we show that surface functionalization is the most important factor in designing an efficient adsorbent for CO2 capture. Systematic Monte Carlo simulations revealed that adsorption of CH4 either pure or mixed with CO2 on oxidized nanoporous carbons is only slightly increased by the presence of functional groups (surface dipoles).

The first atomistic modelling-aided reproduction of morphologically defective single walled carbon nanohorns.

A new modelling-aided approach for the atomistic model of single walled carbon nanohorn (SWNH) creation is presented, based on experimental evidence, on realistic potential of carbon-carbon interactions and on molecular simulations. A new model of SWNHs is next used to predict Ar adsorption properties and to check the molecular fundamentals of the adsorption mechanism. The influence of the apex angle value, nanohorn diameter and nanohorn length on the shapes of isotherms, enthalpy, high resolution α(s)-plots and adsorption potential distribution curves is checked.

Applicability of molecular simulations for modelling the adsorption of the greenhouse gas CF4 on carbons.

Tetrafluoromethane, CF(4), is a powerful greenhouse gas, and the possibility of storing it in microporous carbon has been widely studied. In this paper we show, for the first time, that the results of molecular simulations can be very helpful in the study of CF(4) adsorption. Moreover, experimental data fit to the results collected from simulations.

Detecting adsorption space in carbon nanotubes by benzene uptake.

Experimental results of benzene and nitrogen adsorption from gaseous phase and benzene adsorption and kinetics of the process from aqueous solution, measured on a series of eight commercial closed carbon nanotubes, are presented. Additionally we show the results of adsorption on compressed nanotubes. Using simple analytical approach and the analysis of adsorption and kinetics results it is concluded that in the "architecture" of nanotubes very important role has been played by isolated nanotubes.

The influence of the carbon surface chemical composition on Dubinin-Astakhov equation parameters calculated from SF6 adsorption data-grand canonical Monte Carlo simulation.

Using grand canonical Monte Carlo simulation we show, for the first time, the influence of the carbon porosity and surface oxidation on the parameters of the Dubinin-Astakhov (DA) adsorption isotherm equation. We conclude that upon carbon surface oxidation, the adsorption decreases for all carbons studied. Moreover, the parameters of the DA model depend on the number of surface oxygen groups.

Phenol adsorption on closed carbon nanotubes.

We present the results of systematic studies of phenol adsorption on closed commercially available, unmodified carbon nanotubes. Phenol adsorption is determined by the value of tube-specific surface area, the presence of small amount of surface groups influence adsorption only in very small amount. Phenol can be applied as a probe molecule for comparative analysis of tube surface areas.

Simulating the changes in carbon structure during the burn-off process.

Using a simple energetic criterion, we modelled the process of activation of 'soft' activated carbons. Eighteen carbon samples, differing in degree of graphitisation, and obtained using Molecular Dynamics annealing of an amorphous carbon precursor were studied. For all samples, the geometric pore size distribution was calculated using the method proposed by Bhattacharya and Gubbins.

New model describing adsorption from liquid binary mixtures of nonelectrolytes with limited and unlimited miscibility of components.

Using the thermodynamic idea of complementary systems, and based on fundamental concepts of the theory of volume filling of micropores, we derived a new universal model describing adsorption from solutions with limited and unlimited miscibility of components. The model takes into account the differences in collision diameters of adsorbed molecules as well as the competitive nature of adsorption from solutions. The applicability of this new approach is tested against experimental data.

Quantum fluctuations increase the self-diffusive motion of para-hydrogen in narrow carbon nanotubes.

Quantum fluctuations significantly increase the self-diffusive motion of para-hydrogen adsorbed in narrow carbon nanotubes at 30 K comparing to its classical counterpart. Rigorous Feynman's path integral calculations reveal that self-diffusive motion of para-hydrogen in a narrow (6,6) carbon nanotube at 30 K and pore densities below ∼29 mmol cm(-3) is one order of magnitude faster than the classical counterpart. We find that the zero-point energy and tunneling significantly smoothed out the free energy landscape of para-hydrogen molecules adsorbed in a narrow (6,6) carbon nanotube.

Molecular dynamics of zigzag single walled carbon nanotube immersion in water.

The results of enthalpy of immersion in water for finite single-walled carbon nanotubes are reported. Using molecular dynamics simulation, we discuss the relation between the value of this enthalpy and tube diameters showing that the obtained plot can be divided into three regions. The structure of water inside tubes in all three regions is discussed and it is shown that the existence of the strong maximum of enthalpy observed for tube diameter ca.

Microscopic model of carbonaceous nanoporous molecular sieves--anomalous transport in molecularly confined spaces.

To model the equilibrium and transport properties of carbonaceous molecular sieves (CMS) (i.e., carbon membranes, coals, activated carbons with ink-bottle pore geometry, etc.