With first-principle DFT calculations{,} the catalytic activity of heteroatom-doped carbon nanostructures in oxygen reduction reaction is investigated by exploring the active site of B-doped{,} N-doped and (B{,} N)-codoped and analyzing the kinetic pathways of oxygen reduction with the participation of protons. It is found that the heteroatom-doped graphene can become the effective catalysis materials for ORR with four-electron pathway. Especially{,} the formation of epoxide groups may be important for the four-electron processes on B-doped and (B{,} N)-codoped graphene. By the analysis of charge redistribution{,} the formation of active catalytic sites is attributed to the localized positive charge and electronic dipole induced by the dopant.

In this work{,} we report infrared spectra of large neutral and protonated methanol clusters{,} (MeOH)n and H+(MeOH)n{,} in the CH and OH stretching vibrational region in the size range of n = 10-50. The infrared-ultraviolet double resonance scheme combined with mass spectrometry was employed to achieve moderate size selection of the neutral clusters with the addition of a phenol molecule as a chromophore. Infrared dissociation spectroscopy was performed on the protonated methanol clusters by using a tandem quadrupole mass spectrometer to enable the precise size selection of the clusters. While the neutral clusters showed essentially the same spectra in all the observed size range{,} the protonated clusters showed remarkable narrowing of the H-bonded OH stretch band with increasing n. In n [greater-than-or-equal] [similar]30{,} the spectra of the neutral and protonated clusters become almost identical. These spectral features demonstrate that hydrogen bond networks of methanol prefer simple cyclic structures (or {"}bicyclic{"} structures in protonated methanol) and branching of the hydrogen bond networks (side-chain formation) is almost negligible. Implications of the spectra of the clusters are also discussed by comparison with spectra of bulk phases.

A p-T phase diagram of graphene nanoribbons (GNRs) terminated by hydrogen atoms is established based on first-principles calculations, where the stable phase at standard conditions (25 degrees C and 1 bar) is found to be a zigzag GNR (zzGNR). The stability of this new GNR is understood based on an electron-counting model, which predicts semiconducting nonmagnetic zzGNRs. Quantum confinement of Dirac fermions in the stable zzGNRs is found to be qualitatively different from that in ordinary semiconductors. Bifurcation of the band gap is predicted to take place, leading to the formation of polymorphs with distinct band gaps but equal thermodynamic stability. A tight-binding model analysis reveals the role of edge symmetry on the band-gap bifurcation.

Graphene is believed to be an excellent candidate material for next-generation electronic devices. However, one needs to take into account the nontrivial effect of metal contacts in order to precisely control the charge injection and extraction processes. We have performed transport calculations for graphene junctions with wetting metal leads (metal leads that bind covalently to graphene) using nonequilibrium Green's functions and density functional theory. Quantitative information is provided on the increased resistance with respect to ideal contacts and on the statistics of current fluctuations. We find that charge transport through the studied two-terminal graphene junction with Ti contacts is pseudo-diffusive up to surprisingly high energies.

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By the incorporation of C into (BN)12 fullerene, our theoretical investigation shows that the hydrogenation reaction on carbon doped \{B11N12C\} cluster is both thermodynamically favored and kinetically feasible under ambient conditions. Without using the metal catalyst, the C atom can work as an activation center to dissociate \{H2\} molecule and provide the free H atom for further hydrogenation on the \{B11N12C\} fullerene, which saves the materials cost in practical applications for hydrogen storage. Moreover, the material curvature also plays an important role in reducing the activation barrier for the hydrogen dissociation on the \{BN\} fullerenes.

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With first-principles DFT calculations, the interaction between Li and carbon in graphene-based nanostructures is investigated as Li is adsorbed on graphene. It is found that the Li/C ratio of less than 1/6 for the single-layer graphene is favorable energetically, which can explain what has been observed in Raman spectrum reported recently. In addition, it is also found that the pristine graphene cannot enhance the diffusion energetics of Li ion. However, the presence of vacancy defects can increase the ratio of Li/C largely. With double-vacancy and higher-order defects, Li ion can diffuse freely in the direction perpendicular to the graphene sheets and hence boost the diffusion energetics to some extent.

Due to the severe self-interaction errors associated with some density functional approximations{,} conventional density functionals often fail to dissociate the hemibonded structure of the water dimer radical cation (H2O)2+ into the correct fragments: H2O and H2O+. Consequently{,} the binding energy of the hemibonded structure (H2O)2+ is not well-defined. For a comprehensive comparison of different functionals for this system{,} we propose three criteria: (i) the binding energies{,} (ii) the relative energies between the conformers of the water dimer radical cation{,} and (iii) the dissociation curves predicted by different functionals. The long-range corrected (LC) double-hybrid functional{,} [small omega]B97X-2(LP) [J.-D. Chai and M. Head-Gordon{,} J. Chem. Phys.{,} 2009{,} 131{,} 174105]{,} is shown to perform reasonably well based on these three criteria. Reasons that LC hybrid functionals generally work better than conventional density functionals for hemibonded systems are also explained in this work.

To assess the accuracy of density functional theory (DFT) methods in describing hydrogen bonding in condensed phases{,} we benchmarked their performance in describing phase transitions among different phases of ice. We performed DFT calculations of ice for phases Ih{,} II{,} III{,} VI and VII using BLYP{,} PW91{,} PBE{,} PBE-D{,} PBEsol{,} B3LYP{,} PBE0{,} and PBE0-D{,} and compared the calculated phase transition pressures between Ih-II{,} Ih-III{,} II-VI{,} and VI-VII with the 0 K experimental values of Whalley [J. Chem. Phys.{,} 1984{,} 81{,} 4087]. From the geometry optimization of many different candidates{,} we found that the most stable proton orientation as well as the phase transition pressure does not show much functional dependence for the generalized gradient approximation and hybrid functionals. Although all these methods overestimated the phase transition pressure{,} the addition of van der Waals (vdW) correction using PBE-D and PBE0-D reduced the transition pressure and improved the agreement for Ih-II. On the other hand{,} energy ordering between VI and VII reversed and gave an unphysical negative transition pressure. Binding energy profiles of a few conformations of water dimers were calculated to understand the improvement for certain transitions and failures for others with the vdW correction. We conclude that vdW dispersion forces must be considered to accurately describe the hydrogen bond in many different phases of ice{,} but the simple addition of the R-6 term with a small basis set tends to over stabilize certain geometries giving unphysical ordering in the high density phases.

Boron nitride (BN) domains are easily formed in the basal plane of graphene due to phase separation. With first-principles calculations{,} it is demonstrated theoretically that the band gap of graphene can be opened effectively around K (or K[prime or minute]) points by introducing small BN domains. It is also found that random doping with boron or nitrogen is possible to open a small gap in the Dirac points{,} except for the modulation of the Fermi level. The surface charges which belong to the [small pi] states near Dirac points are found to be redistributed locally. The charge redistribution is attributed to the change of localized potential due to doping effects. The band opening induced by the doped BN domain is found to be due to the breaking of localized symmetry of the potential. Therefore{,} doping graphene with BN domains is an effective method to open a band gap for carbon-based next-generation microelectronic devices.