High-Accuracy Heats of Formation for Alkane Oxidation: From Small to Large via the Automated CBH-ANL Method.

It is generally challenging to obtain high-accuracy predictions for the heat of formation for species with more than a handful of heavy atoms, such as those of importance in standard combustion mechanisms. To this end, we construct the CBH-ANL approach and illustrate that, for a set of 194 alkane oxidation species, it can be used to produce Δ(0 K) values with 2σ uncertainties of 0.2-0.

Mechanism and theory of d-glucopyranose homogeneous acid catalysis in the aqueous solution phase.

A detailed systematic theoretical study of the mechanism of the homogeneous Brønsted-acid catalysis of d-glucose in aqueous solution phase ("acid hydrolysis") is reported. G4MP2 with the SMD solvation model at B3LYP/6-31G(2df,p) are employed to compute the free energies of the molecular and ionic species pertaining to the isomerization, protonation, hydrogen cation transfer and decomposition processes of d-glucopyranose in aqueous solution phase. This information is used to hypothesise a reaction mechanism that is of improved accuracy and completeness from the existing art.

Like-charge ion pairs of hydronium and hydroxide in aqueous solution?

The like-charge ion pairings of hydronium and hydroxide were investigated using both ab initio cluster calculations and QM/MM-MD aqueous simulations. While only a two-water-bridged H3O(+)(H2O)2H3O(+) is found in hydronium cluster calculations, three clusters of HO(-)(H2O)2HO(-), HO(-)(H2O)3HO(-) and HO(-)(H2O)4HO(-) are stable dihydroxide aggregates. In addition, an interesting yet very stable parallelogram structure of [O-H···H-O](2-) without any bridging water was also discovered using QM/MM-MD simulations.

A priori prediction of heats of vaporization and sublimation by EFP2-MD.

New theoretical procedures were proposed for the heats of vaporization (ΔHvap) and sublimation (ΔHsub) predictions by adopting effective fragment potential version 2-molecular dynamics (EFP2-MD) simulations. The particular EFP2, as generated by HF/6-31++G(2d,2p), yielded excellent results in the predictions of ΔHvap, where mean absolute deviation (MAD) and root-mean-square deviation (RMSD) for 16 molecules were 0.34 and 0.

Which hydrogen atom of toluene protonates PAH molecules in (+)-mode APPI MS analysis?

A previous study (Ahmed, A. et al., Anal.

Interionic hydration structures of NaCl in aqueous solution: a combined study of quantum mechanical cluster calculations and QM/EFP-MD simulations.

The association process of NaCl in aqueous solution was studied by a combination of quantum mechanical calculations on NaCl(H(2)O)(n) (n = 1-6) clusters and quantum mechanical/effective fragment potential-molecular dynamics (QM/EFP-MD) simulations for NaCl in 292 EFP waters. The interionic hydration structures (IHSs) were topologically classified as "ring" (R), "half-bridge" (H), and "full-bridge" (F) types on the basis of the quantum mechanical calculations. Subsequent IHS analysis on QM/EFP-MD simulations revealed that the NaCl contact ion pair (CIP) mainly involved R type hydration structures while the solvent-separated ion pair (SSIP) was composed of two different groups of F-type hydration structures.

Hydrophobic and hydrophilic associations of a methanol pair in aqueous solution.

The association dynamics of a methanol pair in aqueous solution were theoretically studied with QM/EFP-MD and quantum mechanical methods. Stable contact pairs and solvent separated configurations (SS) were found from simulations with a free energy barrier of 2 kcal/mol, revealing the strong tendency of methanol association. The stable contact pairs were further identified as the hydrophobic (CP(A)) and hydrophilic (CP(B)) species, with the CP(A) having a larger population.

Direct simulations of anharmonic infrared spectra using quantum mechanical/effective fragment potential molecular dynamics (QM/EFP-MD): methanol in water.

One of the most stringent tests for chemical accuracy of a hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulation method would be to directly compare the calculated vibrational spectra with the corresponding experimental results. Here, the applicability of hybrid QM/effective fragment potential (EFP) to the simulations of methanol infrared spectra is investigated in detail. It is demonstrated that the QM/EFP simulations in combination with time correlation function theory yield not only the fundamental transition bands but also the major overtone and combination bands of methanol dissolved in water in both mid- and near-IR regions.

Adsorption mechanisms of isoxazole and oxazole on Si(100)-2 × 1 surface: Si-N dative bond addition vs. [4+2] cycloaddition.

The surface reaction pathways of isoxazole and oxazole on Si(100)-2 × 1 surface were theoretically investigated. They both form a weakly bound Si-N dative bond adduct on Si(100)-2 × 1 surface. In the case of isoxazole, the barrierlessly formed Si-N adduct is the most important surface product, that cannot be easily converted into other species.

Gold(III) six-membered N^C^N pincer complexes: synthesis, structure, reactivity and theoretical calculations.

The first six-membered gold(III) N^C^N pincer complex was obtained in good yield, under very mild conditions, by transmetalation of [Hg(κC-N^C^N)Cl] (N^CH^N = 1,3-bis(pyridin-2-ylmethyl)benzene, HL(1)) with Na[AuCl(4)]. The X-ray crystal structure of [Au(N^C^N)Cl][PF(6)] showed that the fused six-membered metallacycles each exist in a strongly puckered boat conformation. As shown by the (1)H NMR spectra in various solvents, the same structure is also retained in solution: no inversion of the six-membered metallacycles is observed in DMSO up to 95 °C.

Ping-pong at gold: proton jump between coordinated phenyl and eta1-benzene ligands, a computational study.

A DFT computational investigation predicts that the Au(III) complex (bpy)Au(C(6)H(5))(2+) reacts with benzene to furnish square planar (bpy)Au(C(6)H(5))(eta(1)-C(6)H(6))(2+). Intramolecular processes that occur within this species have been located, and the energetics of all processes have been quantified. The dynamic processes that have been identified are (1) benzene ring rotation with respect to Au, (2) direct hydrogen transfer from the benzene to the phenyl ligand, (3) hydrogen transfer from the ipso to the ortho positions in the coordinated benzene ligand, and (4) hydrogen transfer from the benzenium ligand formed by the ipso/ortho isomerization to the phenyl ligand.

Adsorption reactions of dimethylaluminum isopropoxide and water on the H/Si(100)-2 x 1 surface: initial reactions for atomic layer deposition of Al2O3.

The surface reaction pathways of dimethylaluminum isopropoxide (DMAI) and water with the H/Si(100)-2 x 1 surface were theoretically investigated with SIMOMM:MP2/6-31G(d). The oxygen atom in DMAI stabilizes an initial complex, facilitating the approach of DMAI to the surface. The methane loss reaction, propane loss reaction, methylation, hydrogen loss reaction, and ring closing reaction channels of the DMAI-surface reactions were identified.