A general recursion algorithm is described for calculating kinematical diffraction intensities from crystals containing coherent planar faults. The method exploits the self-similar stacking sequences that occur when layers stack non-deterministically. Recursion gives a set of simple relations between average interference terms statistical crystal, which can be solved as simultaneous equations. diffracted intensity polycrystalline sample given by incoherent sum scattered over an ensemble...

The best ZIF structure found in screening of databases containing over half a million nanoporous materials for vehicular methane storage is shown.

We here describe a database of computationally predicted zeolite-like materials. These crystals were discovered by Monte Carlo search for Positions Si atoms as well unit cell, space group, density, and number crystallographically unique explored in the construction this database. The contains over 2.6 M structures. Roughly 15% these are within +30 kJ mol(-1) α-quartz, band which most known zeolites lie. structures have topological, geometrical, diffraction characteristics that similar to...

We describe a new, biased Monte Carlo scheme to determine the crystal structures of zeolites from powder diffraction data. test method on all publicly known zeolite materials, with success in cases. show that parallel tempering is powerful supplement Carlo.

Concomitant with the evolution of biological diversity must have been mechanisms that facilitate evolution, because essentially infinite complexity protein sequence space. We describe how evolvability can be an object Darwinian selection, emphasizing collective nature process. quantify our theory computer simulations evolution. These demonstrate rapid or dramatic environmental change leads to selection for greater evolvability. The selective pressure large-scale genetic moves such as DNA...

Detailed balance is an overly strict condition to ensure a valid Monte Carlo simulation. We show that, under fairly general assumptions, simulation need satisfy only the weaker condition. Not does our proof that sequential updating schemes are correct, but also it establishes correctness of whole class new methods simply leave Boltzmann distribution invariant.

We present a database of computationally predicted zeolite-like materials. The materials were identified by Monte Carlo search Si atom positions as the number unique atoms, density, space group, and unit cell crystalline material was systematically explored. Over 2.7M structures identified, with roughly 10% within +30 kJ/mol energetic band above α-quartz in which known zeolites lie. Predicted this have geometric topological characteristics similar to that zeolites. Known are shown lie on...

We present a computational method to identify zeolite-like frameworks by sampling zeolite figure of merit. Monte Carlo methods, including simulated annealing, are used perform the sampling. discuss construction database hypothetical with this approach and how may be search for new structures specific material properties interest.

We describe a computational procedure to predict chemically synthesizable organic structure directing agents (OSDAs) for zeolites. To identify these structure-directing agents, we apply transformations from chemistry library of available reagents. The compounds are scored based upon stability under synthesis conditions, rigidity, volume, geometric compatibility, and energy interaction with the target zeolite. illustrate method on three zeolites AEI, ITE, STF. This can be used search novel,...

Significance Zeolites and zeolite-like molecular sieves are used as adsorbents heterogeneous catalysts to prepare a wide variety of products ranging from gasoline monomers for polymers such polyethylene terephthalate, which is in plastic bottles. Pharmaceuticals, pesticides, fragrances, components food can contain chiral centers. Here, we enantioenriched polycrystalline samples sieve show that this type porous material function an adsorbent separate molecules catalyst perform reactions. This...

Abstract Crystalline molecular sieves are used in numerous applications, where the properties exploited for each technology direct consequence of structural features. New materials typically discovered by trial and error, many cases, organic structure‐directing agents (OSDAs) to their formation. Here, we report first successful synthesis a specified sieve through use an OSDA that was predicted from recently developed computational method constructs chemically synthesizable OSDAs....

Zeolites play numerous important roles in modern petroleum refineries and have the potential to advance production of fuels chemical feedstocks from renewable resources. The performance a zeolite as separation medium catalyst depends on its framework structure. To date, 213 types been synthesized >330,000 thermodynamically accessible structures predicted. Hence, identification optimal zeolites for given application large pool candidate is attractive accelerating pace materials discovery....

We have micromachined a silicon-chip device that transports DNA with Brownian ratchet rectifies the motion of microscopic particles. Transport properties for 50mer agree theoretical predictions, and diffusion constant agrees previous experiments. This type micromachine could provide generic pump or separation component other charged species as part microscale lab-on-a-chip. A reduced feature size produce size-based molecules, applications including detection single nucleotide polymorphisms.

Biological diversity has evolved despite the essentially infinite complexity of protein sequence space. We present a hierarchical approach to efficient searching this space and quantify evolutionary potential our with Monte Carlo simulations. These simulations demonstrate that nonhomologous juxtaposition encoded structure is rate-limiting step in production new tertiary folds. Nonhomologous “swapping” low-energy secondary structures increased binding constant simulated by ≈10 7 relative base...

Special k: Pure silica zeolites (PSZs) have been shown experimentally to display a remarkably higher elastic modulus than amorphous porous silicas at any given porosity or dielectric constant (k) value as result of their crystalline structure. The combined experimental and theoretical findings suggest that PSZs the necessary properties for use next generation low-k insulators. Supporting information this article is available on WWW under...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFramework crystal structure solution by simulated annealing: test application to known zeolite structuresMichael W. Deem and John M. NewsamCite this: J. Am. Chem. Soc. 1992, 114, 18, 7189–7198Publication Date (Print):August 1, 1992Publication History Published online1 May 2002Published inissue 1 August 1992https://doi.org/10.1021/ja00044a035RIGHTS & PERMISSIONSArticle Views496Altmetric-Citations106LEARN ABOUT THESE METRICSArticle Views are the...

We examine how the structure of world trade network has been shaped by globalization and recessions over last 40 years. show that treating as an evolving system, theory predicts is more sensitive to recessionary shocks recovers slowly from them now than it did years ago, due structural changes in induced globalization. also recession-induced change leads increased hierarchical global for a few after recession.

The recent emergence of H1N1 (swine flu) illustrates the ability influenza virus to create antigens new human immune system, even within a given hemagglutinin and neuraminidase subtype. This strain is sufficiently distinct, for example, from A/Brisbane/59/2007 (H1N1)-like in 2008/09 Northern hemisphere vaccine that protection not expected be substantial. system responds primarily five epitope regions protein. By determining fraction amino acids differ between viral challenge dominant...

Zeolite A (LTA) has many large-scale uses in separations and ion exchange applications. Because of the high aluminum content lack high-temperature stability, applications catalysis, while highly desired, have been extremely limited. Herein, we report a robust method to prepare pure-silica, aluminosilicate (product Si/Al = 12–42), titanosilicate LTA fluoride media using simple, imidazolium-based organic structure-directing agent. The material is an active catalyst for methanol-to-olefins...