Metal–organic frameworks (MOFs) are porous crystals with the potential to improve many industrial gas separation processes. Because there is a practically unlimited number of different MOFs, which vary in their pore geometry and chemical composition, it challenging find best MOF for given application. Here, we applied high-throughput computational methods rapidly explore thousands possible library starting materials, context Xe/Kr separation. We generated over 137 000 structurally diverse...

Molecular simulations have been used to estimate the properties of three-component mixtures whose constituents were chosen represent chemical families found in paving asphalts. Naphthene aromatics and saturates represented by 1,7-dimethylnaphthalene n-C22, respectively. Two different asphaltene model structures considered. The first has a large aromatic core with few short side chains; second contains moderate size larger branches. Both types proposed recent literature based on experimental...

The fatigue-cracking life of an asphalt mixture measured in the laboratory is generally a small fraction observed field. One reasons for this large difference self-healing property binders. Self-healing process that reverses growth fatigue cracks during rest periods between load applications. A thorough understanding healing mechanism required to accurately model and predict influence on mixtures. Previous studies have used experimental evidence demonstrate correlation chemistry functional...

Molecular dynamics simulation was used to calculate rotational relaxation time, diffusion coefficient, and zero-shear viscosity for a pure aromatic compound (naphthalene) aliphatic components in model asphalt systems over temperature range of 298-443 K. The were chosen previously represent real asphalt. Green-Kubo Einstein methods estimate at high (443.15 K). Rotational times calculated by nonlinear regression orientation correlation functions modified Kohlrausch-Williams-Watts function....

Physical properties and microstructures of computational model asphalts were investigated using molecular dynamics simulations in an all-atom framework. A new asphalt is proposed that targeted toward core AAA-1 the Strategic Highway Research Program (SHRP) based on elemental composition speciation. Individual compounds chosen from literature to represent asphaltene, polar aromatic, naphthene saturate, with interactions ranked Hansen solubility parameters. The density thermal expansion...

The dynamics properties of a new “next generation” model asphalt system that represents SHRP AAA-1 using larger molecules than past models is studied molecular simulation. contains 72 distributed over 12 molecule types range from nonpolar branched alkanes to polar resins and asphaltenes. Molecular weights 290 890 g/mol. All-atom simulations conducted at six temperatures 298.15 533.15 K provide wealth correlation data. modified Kohlrausch-Williams-Watts equation was regressed reorientation...

Molecular simulations were used to analyze orientations of molecules within model asphalt mixtures. After choosing typical compounds represent resin, maltene, and asphaltene components, molecular structures in two ternary mixtures studied. The following conclusions are obtained from analyzing simulation results: (1) For nearest molecules, between neighboring affected by molecule structure temperature. At high temperature, with long alkane branches prefer pack almost parallel; at low...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGeometric analysis of diffusion pathways in glassy and melt atactic polypropyleneMichael L. Greenfield Doros N. TheodorouCite this: Macromolecules 1993, 26, 20, 5461–5472Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https://pubs.acs.org/doi/10.1021/ma00072a026https://doi.org/10.1021/ma00072a026research-articleACS PublicationsRequest reuse permissionsArticle...

Molecular structures proposed in the literature as representative of asphaltenes attempt to encompass results numerous experiments and quantum mechanics calculations. This work demonstrates that certain features chemical bonding lead directly high energies thus low relative occurrence probabilities. Hartree–Fock, density functional theory, classical force field calculations indicate such nonplanar aromatic rings occur recently literature. Energy differences for altered pendant group...

Molecular level calculations targeting the behaviour of asphaltenes, resins and bitumens are reviewed with an objective relating molecular structure interactions to macroscale physical, chemical mechanical properties. The review discusses dynamics simulations asphaltenes briefly summarises elucidation, quantum mechanics, coarse graining thermodynamic model approaches. architecture in plays important role, continental archipelago showing different packing tendencies isolated systems...

Water transport is one of the major factors responsible for moisture damage in asphalt pavements. To study thermodynamics and kinetics water bitumen to uncover microscale mechanisms moisture-induced damage, molecular dynamics simulations were performed up 600 ns water–bitumen systems with realistic contents that varied from 0 1.76 wt%. Hydrogen bonding interactions clustering molecules at various combinations temperature content investigated, their effects on self-diffusion coefficient...

A multidimensional transition state theory (TST) approach is formulated for the study of elementary jumps involved in diffusion a gaseous penetrant glassy polymer, taking explicitly into account coupling between polymer and degrees freedom along each jump. In this approach, an initial picture states (local minima potential energy + system) "macrostates" (i.e., collections communicating over barriers small relative to kBT) obtained through geometric analysis accessible volume representative...

The dynamical properties of a complex system incorporate contributions from the diverse components which it is constituted. To study this relationship in multicomponent system, relaxation times based on rotation autocorrelation functions molecular dynamics simulations were analyzed for molecules two sets unmodified and polymer-modified model asphalt/bitumen systems over 298–473 K. asphalt proposed previously to approximate chemical mechanical real asphalts. Relaxations modeled using modified...

Previous molecular dynamics simulations have shown that the diffusion of a penetrant in glassy polymer involves occasional jumps between cavities through opening "neck", and thus, because this is rare event, coefficient can be estimated using transition-state theory. We treat process as unimolecular rearrangement develop semiempirical means estimating activation energy, frequency factor jump length. The energy obtained by treating continuous solid calculating required to expand neck...

A coarse-grained method for simulating diffusion of a small molecule within glassy polymer was developed and implemented. The builds on our previous work in which molecular-level jump rates between likely sorption states were calculated with multidimensional transition-state theory incorporating explicit chain motions that accompany each jump. In this we first use reverse Monte Carlo approach to generate large microstructures paths whose size, connectivity, rate constant distributions match...

Tiranium, vanadium, and chromium trichlorides react with ethylenediamine (en) propylenediamine (pn) to yield paramagnetic complexes of the type M en3Cl3 pn3Cl3, those in each group being isomorphous one another. Conductance infrared studies indicate that all chlorine atoms are ionic, hence contain tris-bidentate cations. The electronic spectra discussed assignments for ligand-field bands given. strength is virtually identical ethylenediamine. magnetic moments (4000–200 cm.–1) have been...

The ligands bis-(o-dimethylarsinophenyl)methylarsine (o-TAS) and tris-1,1,1-(dimethylarsinomethyl)ethane (ν-TAS) react with titanium vanadium tetrachlorides to yield monomeric, non-electrolytic complexes of the type [MCl4,TAS], for which n.m.r. measurements demonstrate that all three arsenic atoms each ligand are coordinated metal. in these therefore seven-co-ordinate. rapidly hydrolysed moist air, those forming definite [VOCl2,TAS].The trihalides chromium triarsines form neutral monomeric...

Abstract Multidimensional transition-state theory was used to simulate methane jump motions in glassy atactic polypropylene at 233 K the limit of small concentrations. Transition states were found with respect both penetrant and polymer degrees freedom, using all generalized coordinates associated atoms interacting penetrant. Animations followed multidimensional reaction coordinate for three different jumps. The mechanism involved retracting form a channel, by motion through channel. Methyl...

Studies indicate a crucial cell membrane role in the antibiotic resistance of Staphylococcus aureus. To simulate its structure and dynamics, complex molecular-scale computational representation S. aureus lipid bilayer was developed. Phospholipid types their amounts were optimized by reverse Monte Carlo to represent characterization data from literature, leading 19 different phospholipid that combine three headgroups [phosphatidylglycerol, lysyl-phosphatidylglycerol (LPG), cardiolipin] 10...