Real-World Predictions from Ab Initio Molecular Dynamics Simulations - Multiscale Molecular Methods in Applied Chemistry - page 147

(N3) by I in acetonitrile. A barrier-free complex formation of the oxidized dye
with both I and I 2 , and facile dissociation of I 2 and I 3 from the reduced dye, were
determined to be key steps in this process. The authors also carried out in situ
vibrational spectroscopy and could thus confirm the reversible binding of I 2 to the
thiocyanate group. Furthermore, Schiffmann et al. were able to simulate the elec-
trolyte near the interface and found that acetonitrile is able to cover the (101)
surface of anatase with a passivating layer that inhibits direct contact of the redox
mediator with the oxide [ 229 , 230 ]. It was also observed that the solvent structure
specifically enhances the concentration of I at a distance which further favors
rapid dye regeneration.
5 Summary
This review serves as an overview of modern aspects concerning methodology as
well as applications of ab initio molecular dynamics simulations.
First, a general introduction into the ab initio molecular dynamics simulations
technique of the Car-Parrinello type was given. The derivation of forces and
equations of motion were explained. In the last part of this introductory section,
generalizations according to Niklasson were detailed.
Next, difficulties encountered in ab initio molecular dynamics simulations were
discussed. Topics covered were massive parallelization to address computer time
problems, basis set considerations, density functionals and van der Waals
interactions, relativistic corrections, and new integration schemes. Several simula-
tion techniques used to gain chemical insight were summarized. Enhanced sam-
pling methods, metadynamics and other methods to explore free energy surfaces,
reaction pathways and transition states were covered. Simulation of spectra (IR,
NMR, EXAFS) from ab initio molecular dynamics simulations was the subject of
the remaining paragraphs.
The last section was devoted to a range of real-world applications treated with ab
initio molecular dynamics simulations. Results of gas to liquid phase transition
simulations, structural and dynamical properties of liquids such as common
solvents as well as the emerging neoteric media of ionic liquids were presented.
After a short discussion of chemical reactions concerning homogeneous catalysis,
we presented an overview of electrochemical reactions and related processes.
We hope this choice of topics showed that, despite some difficulties, ab initio
molecular dynamics simulation is nowadays capable of analyzing and predicting
real-world processes, especially those which are poorly accessible through
experiments or other theoretical techniques.
Acknowledgment This work was supported by the DFG, in particular by the projects KI-768/4-2,
KI-768/5-1, KI-768/5-2, KI-768/5-3, KI-768/6-1 and KI-768/7-1.