Eighth Condensed Phase and Interfacial Molecular Science (CPIMS)

elatively large fraction in BN–C sheets, or higher Raman intensities as shown in Fig.2
(a) and (c). Furthermore, Fig. 2(d) shows that the occurrence of embedded C2 and
benzene C6 units is likely. This finding supports the experimental observations by
Krivanek et al. (O.L. Krivanek et al. Nature (London) 464 (2010) 571) and Ci et al. (L.
Ci et al. Nature Mater. 9 (2010) 430). Indeed, the finding of the armchair connection of
graphene fragments to BN can be understood by the fact that graphene sheets with
armchair edges are metallic. In addition, the weaker C–B and C–N bond strengths
relative to C–C are consistent with the redshift of the Raman peak around 1580 cm −1 .
Future Plans
Quantum wavepacket and kinetics studies of photoinduced dynamics of O2 on
TiO2(110)
One ongoing project is to carry out quantum wavepacket dynamics and kinetics
calculation for studying the photoinduced dynamics of the O2/TiO2(110) system in
collaboration with the BNL Surface Chemical Dynamics Group. This research is an
extension of research from our gas-phase molecular dynamics studies toward the
gas/solid interface. Here, we will focus on the non-adiabatic effects resulting from the
interactions between the photo-excited electrons and the adsorbed molecules on surfaces,
and on the electron-hole (e - -h + ) recombination in the TiO2 case. The non-adiabatic effects
will be investigated using a time-dependent wavepacket approach based on the Luntz et
al.’s and/or Lara-Castlells and Krause’s models (e.g. J. Chem. Phys. 118 (2003) 5098;
124 (2006) 244702). The hot electron dynamics at surfaces will be simulated in a kinetics
manner. We have developed a kinetic graph theory (KGT) method for studying the e � -h +
recombination of TiO2. Preliminary results show that the photocatalytic efficiency is
mainly limited by the fast delocalization of excited electrons and their recombination
with holes.
The interactions between O2 and
reduced TiO2(110) surface have been
investigated by using a DFT method,
based on a compact O2-(Ti15O28OH) -
cluster model. It has a comparable band
gap with that of the TiO2 crystal.
Results show that the triplet state of the
reduced TiO2(110) surface with an Ovacancy
is more stable (about 0.22 eV)
than the singlet one. An oxygen
molecule can strongly chemically
adsorb at the vacancy site via either a
parallel (in O2 2- ) or perpendicular (in
O2 - ) structure, where the former is
slightly more stable (by about 0.38 eV).
Although the dissociated product
channel of O2 at the vacancy site is
Figure 3. Relative HOMO/LUMO energy levels
(in au w.r.t. vacuum) of TiO2(110) model
with/without an O-vacancy.
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