The method of dispersion correction as an add-on to standard Kohn-Sham density functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coefficients and cutoff radii that are both computed from first principles. The coefficients for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination numbers (CN). They are used to interpolate between dispersion coefficients of atoms in different chemical environments. The method only requires adjustment of two global parameters for each density functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of atomic forces. Three-body nonadditivity terms are considered. The method has been assessed on standard benchmark sets for inter- and intramolecular noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean absolute deviations for the S22 benchmark set of noncovalent interactions for 11 standard density functionals decrease by 15%-40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C(6) coefficients also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.

http://dns2.asia.edu.tw/~ysho/YSHO-English/1000%20WC/PDF/J%20Che%20Phy132,%20154104.pdf

A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu

The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited

https://www.uta.edu/rfmems/GI_Sensor/papers/ac040049d.pdf

Fiber-Optic Chemical Sensors and Biosensors

Protein–protein interactions have a key role in most biological processes, and offer attractive opportunities for therapeutic intervention. Developing small molecules that modulate protein–protein interactions is difficult, owing to issues such as the lack of well-defined binding pockets. Nevertheless, there has been important progress in this endeavour in recent years. Here, we use illustrative examples to discuss general strategies for addressing the challenges inherent in the discovery and characterization of small-molecule inhibitors of protein–protein interactions.

Small-molecule inhibitors of protein–protein interactions: progressing towards the dream

Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts.

Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity

The process of converting methanol to hydrocarbons on the aluminosilicate zeolite HZSM-5 was originally developed as a route from natural gas to synthetic gasoline. Using other microporous catalysts that are selective for light olefins, methanol-to-olefin (MTO) catalysis may soon become central to the conversion of natural gas to polyolefins. The mechanism of methanol conversion proved to be an intellectually challenging problem; 25 years of fundamental study produced at least 20 distinct mechanisms, but most did not account for either the primary products or a kinetic induction period. Recent experimental and theoretical work has firmly established that methanol and dimethyl ether react on cyclic organic species contained in the cages or channels of the inorganic host. These organic reaction centers act as scaffolds for the assembly of light olefins so as to avoid the high high-energy intermediates required by all “direct” mechanisms. The rate of formation of the initial reaction centers, and hence the d...

The mechanism of methanol to hydrocarbon catalysis.

Physical Organic Chemistry of Solid Acids: Lessons from in Situ NMR and Theoretical Chemistry

In situ 13C NMR measurements on samples prepared using a pulse-quench catalytic reactor show that the 1,3-dimethylcyclopentenyl carbenium ion (1) is an intermediate in the synthesis of toluene from ethylene on zeolite catalyst HZSM-5. Cation 1 forms in less than 0.5 s when ethylene is pulsed onto the catalyst bed at 623 K, and its presence obviates the kinetic induction period for conversion of a subsequent pulse of dimethyl ether, or methanol, into olefins (MTO chemistry). The kinetic induction period returns when the interval between pulses is many times the half-life of 1 in the catalyst bed. Density functional theory calculations (B3LYP/ 6-311G**) on a cluster model of the zeolite confirm that 1 is stable in the zeolite as a free cation and suggest why the alternative framework alkoxy is not observed. A π complex of the neutral cyclic diene is only 2.2 kcal/mol higher in energy than that of the ion pair. Theoretical (GIAO-MP2/tzp) 13C isotropic shifts of isolated 1 are in good agreement with the exper...

Roles for Cyclopentenyl Cations in the Synthesis of Hydrocarbons from Methanol on Zeolite Catalyst HZSM-5

Pulse-quench catalytic reactor studies reveal a carbon-pool mechanism in methanol-to-gasoline chemistry on zeolite hzsm-5

Recent experimental work has shown that methanol to olefin (MTO) catalysis on microporous solid acids proceeds through a hydrocarbon pool mechanism with methylbenzenes frequently acting as the most important reaction centers. Other recent experimental evidence suggests that side-chain methylation is more important than an alternative paring (ring contraction−expansion) mechanism. The present investigation uses density functional theory B3LYP/cc-pVTZ//B3LYP/6-311G* and G3(MP2) calculations to model many of the features of the side-chain mechanism. We first calculated at the G3(MP2) level the heats of formation of 43 neutral alkybenzenes to predict the thermodynamics for methylation reactions. The G3(MP2) results predict that sequential methylation of benzene rings with fewer than four methyl groups will preferentially occur on the ring, resulting in the series toluene, 1,3-dimethylbenzene, 1,2,4-trimethylbenzene, and 1,2,4,5-tetramethylbenzene. With the addition of another methyl group side-chain methylati...

John B. Nicholas

Papers

The mechanism of methanol to hydrocarbon catalysis.

Physical Organic Chemistry of Solid Acids: Lessons from in Situ NMR and Theoretical Chemistry

Roles for Cyclopentenyl Cations in the Synthesis of Hydrocarbons from Methanol on Zeolite Catalyst HZSM-5

Pulse-quench catalytic reactor studies reveal a carbon-pool mechanism in methanol-to-gasoline chemistry on zeolite hzsm-5

Theoretical Study of the Methylbenzene Side-Chain Hydrocarbon Pool Mechanism in Methanol to Olefin Catalysis