By applying the nonequilibrium Green function formalism
combined
with density functional theory, we have investigated the electronic
transport properties of the C60 dimer and its endohedral
complex Li@C60 dimer. Our results show that the doping
of Li atoms significantly changes the transport properties of the
C60 dimer. Negative differential resistance is found in
such systems. Especially, the doping of Li atoms can lead to a much
larger negative differential resistance at much lower bias, and it
is quite evident from the plot of differential conductance versus
bias. The negative differential resistance behavior is understood
in terms of the evolution of the transmission spectrum and projected
density of states spectrum with applied bias combined with molecular
projected self-consistent Hamiltonian states analyses.
Using the density functional theory with the generalized gradient approximation, we have examined the stability and the catalytic properties of Au16 gold cage structure supported on graphane. The substantially improved stability is confirmed by the first-principles molecular dynamics simulation at the temperature above 500 K. The energy barrier is only 0.47 eV for the Langmuir–Hinshelwood oxidation process for a CO coadsorbed on catalyst with an O2 molecule. The following Eley–Rideal oxidation process can happen almost simultaneously for its low activation barrier of ∼0.13 eV. A simple model to mimic the situation of the full coverage of CO on gold catalyst can experience oxidation by overcoming 0.63 eV energy barrier, which suggests the CO tolerant property of the complex graphane-based gold catalyst.
On the basis of detailed studies
of structural and electronic properties
with first-principles calculations, we have carefully analyzed enhanced
H2 splitting catalyzed by the early transition metals that
substitutionally doped in the top layer and the subsurface of an ideal
flat Al surface and that at the edge site of a stepped surface. The
3d orbitals facilitating Kubas interaction significantly reduce the
activation energy of H2 splitting catalyzed by a transition
metal doped in the top surface. The catalyst doped in the subsurface
could not develop Kubas interaction with H2 because of
the screening from the charge distributed on the top surface, whose
role could be understood by combining the structural deformation induced
by the doping, the attraction of the dopant to the electrons distributed
around Al atoms in the top layer, and the d orbital attendance in
the reaction. For the sake of recycling perspectives of the doped
catalyst, the diffusion of the dissociated H atoms has also been studied.
Thus, the Sc and Ti doping at the lower edge site of the stepped surface
are better for their low activation energies. The atomic size and
electronegativity could be used to aid new catalyst design for enhancing
the hydrogen recharge properties of metal alanate hydrides. Accordingly,
the near-surface alloying of Sc, Ti, Zr, Nb, Hf, and Ta in the aluminum
surface could be expected to have superior catalytic properties.
Based on spin-polarized first-principles density functional theory in conjunction with nonequilibrium Green's function method, the spin transport properties of transition metal (TM)-dibenzotetraaza[14]annulene (DBTAA) complexes (TM = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) sandwiched between two Au electrodes are investigated. The results show that Fe-and Co-DBTAA can display perfect spin filtering behavior in a wide bias voltage region. Moreover, it is found that the connected position of anchoring group on the complexes affect significantly the spin filtering efficiency. The observed spin filtering behavior is explained by the spin-resolved transmission spectrum and molecular projected self-consistent Hamiltonian state analyses.
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