The effects of adsorbing simple aromatic molecules on the electronic structure of graphene were systematically examined by first-principles calculations. Adsorptions of different aromatic molecules borazine (B3N3H6), triazine (C3N3H3), and benzene (C6H6) on graphene have been investigated, and we found that molecular adsorptions often lead to band gap opening. While the magnitude of band gap depends on the adsorption site, in the case of C3N3H3, the value of the band gap is found to be up to 62.9 meV under local density approximation—which is known to underestimate the gap. A couple of general trends were noted: (1) heterocyclic molecules are more effective than moncyclic ones and (2) the most stable configuration of a given molecule always leads to the largest band gap. We further analyzed the charge redistribution patterns at different adsorption sites and found that they play an important role in controling the on/off switching of the gap—that is, the energy gap is opened if the charge redistributes to between the C–C bond when the molecule is adsorbing on graphene. These trends suggest that the different ionic ability of two atoms in heterocyclic molecules can be used to control the charge redistribution on graphene and thus to tune the gap using different adsorption conditions.

Water decomposition process was investigated by ab initio molecular dynamic simulations using a model of (H2O)2+ clusters. The proton transfer (PT) process from the cationic H-donor water to the H-acceptor water for the formation of (HO[radical dot])[middle dot]H3O+ was predicted as about 90 fs on average calculated at CCSD level of theory. The valence-electron transfer (VET) process through the formation of hemibond interaction between neutral and cationic water{,} (H2O)2+{,} was also identified in several collected trajectories. Both PT and VET processes were found to propagate along two orthogonal reaction coordinates{,} the former was through an intermolecular hydrogen bond and the latter required oxygen-oxygen hemibonding. Significant difference of the theoretical electronic transitions along the VET trajectories was also observed in comparison with the non-VET cases{,} being calculated at SAC-CI level. The strong absorption features of hemibonding (H2O)2+ may introduce an interesting consideration for experimental design to monitor the water decomposition process.

The interaction between graphene and a SiO 2 surface has been analyzed with first-principles DFT calculations by constructing the different configurations based on α-quartz and cristobalite structures. The fact that single-layer graphene can stay stably on a SiO 2 surface is explained based on a general consideration of the configuration structures of the SiO 2 surface. It is found that the oxygen defect in a SiO 2 surface can shift the Fermi level of graphene down which opens up the mechanism of the hole-doping effect of graphene adsorbed on a SiO 2 surface observed in a lot of experiments.

Experimental studies on reaction dynamics by use of molecular beams and oriented molecular beams are reviewed in order for looking closer to chemical reactions as well as photodissociations at the molecular level. We discuss about versatility and usefulness of the electrostatic hexapole sate-selector as a non-destructive selector for molecular structure analysis. Some experimental evidences on novel reaction dynamics in photodissociation and stereodynamics are presented followed by concluding remarks and future perspectives for controlling chemical reactions from the point of view of green chemistry, by manipulating molecular orientation without any catalyst nor by applying any external forces like intense electromagnetic field. © 2012 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The magic number behavior of ((CH3)3N)n–H+–H2O clusters at n = 3 is investigated by applying infrared spectroscopy to the clusters of n = 1–3. Structures of these clusters are determined in conjunction with density functional theory calculations. Dissociation channels upon infrared excitation are also measured, and their correlation with the cluster structures is examined. It is demonstrated that the magic number cluster has a closed-shell structure, in which the water moiety is surrounded by three (CH3)3N molecules. The ion core (protonated site) of the clusters is found to be (CH3)3NH+ for n = 1–3, but coexistence of an isomer of the H3O+ ion core cannot be ruled out for n = 3. Large rearrangement of the cluster structures of n = 2 and 3 before dissociation, which has been suggested in the mass spectrometric studies, is confirmed on the basis of the structure determination by infrared spectroscopy.

Depositing particles randomly on a 1D lattice is expected to result in an equal number of particle pairs separated by even or odd lattice units. Unexpectedly, the even-odd symmetry is broken in the self-selection of distances between indium magic-number clusters on a Si(100)-2 x 1 reconstructed surface. Cluster pairs separated by even units are less abundant because they are linked by silicon atomic chains carrying topological solitons, which induce local strain and create localized electronic states with higher energy. Our findings reveal a unique particle-particle interaction mediated by the presence or absence of topological solitons on alternate lattices.

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Cluster expansion provides a powerful tool in materials modeling. It has enabled an efficient prediction of the atomic properties of materials with the combination of the modern quantum calculation theory. To construct an accurate cluster expansion model, a few important cluster figures should be identified. This paper proposes a novel figure selection method based on memetic algorithm (MA), which is a synergy of genetic algorithm (GA) and orthogonal matching pursuit (OMP) based memetic operation. The memetic operation is designed to fine-tunes the solutions of GA and accelerate the convergence of the search. The performance of the proposed method is evaluated on two binary alloy datasets. Comparative study to other state-of-the-art figure selection methods demonstrates that the proposed method is capable of obtaining better or competitive prediction accuracy and searching the figure space efficiently.

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The hydrogen spillover mechanism on B-doped graphene was explicitly investigated by first-principles calculations. By the incorporation of boron into graphene, our theoretical investigation shows that B doping can substantially enhance the adsorption strength for both H atoms and the metal cluster on the substrate. The firmly bound catalytic metal on B-doped graphene can effectively dissociate H2 molecules into H atoms, and the H atom is more likely to migrate from the bridge site of the H-saturated metal to the supporting graphene sheet. Further investigation on the BC3 sheet gives sufficiently low activation barriers for both H migration and diffusion processes; thus, more H atoms are expected to adsorb on BC3 substrate via H spillover under ambient conditions compared with the undoped graphene case. Our result is in good agreement with recent experimental findings that microporous carbon has an enhanced hydrogen uptake via boron substitution, implying that B doping with spillover is an effective approach in the modification of graphitic surface for hydrogen storage applications.

Using a combination of the bond order–length–strength correlation theory, the spin-polarized tight binding method, the first-principles calculations, and the atomistic photoelectron distillation experiments, we investigated the mechanisms of edge-selective generation and hydrogenated modulation of Dirac-Fermi polarons (DFPs) surrounding the atomic vacancies at a graphite surface and at the edges of graphene nanoribbons (GNR). We found that: (i) the \{DFPs\} with a high-spin density at a zigzag-GNR edge and at an atomic vacancy result from the isolation and polarization of the dangling σ-bond electrons of √3d (d is the C–C bond length) distance along the edge by the locally and densely entrapped bonding electrons; (ii) along an armchair-GNR edge and a reconstructed-zigzag-GNR edge, however, the formation of quasi-triple-bond between the nearest edge atoms of d distance prevents the \{DFPs\} from generation; and (iii) hydrogenation reduces the spin density substantially and turns the asymmetric dumb-bell-like density into the spherical-like pz density. A further C 1s photoelectron spectroscopic purification has confirmed that the generation of the \{DFPs\} is associated with two extra peaks of energy states located at the bottom and the top edge of the C 1s band.

The local structures between nano-TiO2 and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI+TFS–) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMI+TFS–) were investigated using high-pressure infrared spectroscopy. No significant changes in C–H spectral features of EMI+TFS– were observed in the presence of nano-TiO2 under ambient pressure. As the EMI+TFS–/nano-TiO2 mixture was compressed to 0.3 GPa, the imidazolium C–H absorptions became two sharp bands at 3108 and 3168 cm–1, respectively, and the alkyl C–H stretching absorption exhibits a new band at 3010 cm–1 associated with a weaker band at 3028 cm–1. It appears that pressure stabilizes the isolated conformations due to pressure-enhanced imidazolium C–H–-nano-TiO2 interactions. Our results also reveal that alkyl C–H groups play non-negligible roles at the conditions of high pressures. The results of BMI+TFS–/nano-TiO2 are remarkably different from what is revealed for EMI+TFS–/nano-TiO2. The spectral features and band frequencies of BMI+TFS–/nano-TiO2 are almost identical to those of pure BMI+TFS– under various pressures. This study demonstrates that changes to the alkyl chain length of the cation could be made to control the order and strength of ionic liquid/nano-TiO2 interactions.

Polynorbornenes appended with anthracene and chiral alanine linkers are synthesized. Hydrogen bonding between the adjacent bisamidic linkers brings adjacent anthracene chromophores in a more suitable orientation for exciton coupling and renders one-handed helical structures for these polymers. Excimer formation is observed from their emission spectra. Monoamidic linkers provide only one hydrogen bond, which would be less robust and result in much lower circular dichroic response. Hydrogen bonding between the adjacent chiral alanine linkers brings appended anthracene in a more suitable orientation for exciton coupling and excimer formation, rendering one-handed helical structures in polynorbornenes. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.