Quantum Molecular Dynamic Simulation of Proton Conducting Materials

Computer simulations are powerful for the understanding of properties, reactions, and processes. Due to the improvement of both computer capabilities and new methods or algorithms, the investigated systems become more and more complex. Nowadays, these tools can be applied to any domain of chemistry to bring fundamental information concerning structures, reactivity, and properties on the components of the system of interest. The fuel-cell applications bring newer challenges, due to the complexity of model systems. The study of proton transport through polymeric membranes is not a routine task, due to the large timescale and the variety of possible mechanisms. The choice of theoretical chemistry allows to avoid any need for assumptions concerning the system. The dynamical processes can be investigated in two different ways: the adiabatic processes, where the system remains in the electronic ground state and the nonadiabatic processeswhere electronic excitation, ionization or charge transfer occur. Only the ways to study adiabatic phenoma will be described here. In order to explore the proton conductivity, quantum molecular dynamics methods are extensively used. There are two different types of ab initio molecular dynamics based on two theories: Born-Oppenheimer and CarParrinello. Both of them use an explicit treatment of the electron interactions. The bonding state of the system can change along the simulation. Therefore, these methods are of great interest to obtain information concerning the transfer of protons. They play a central role in the description of dynamic phenomena, using ab initio or empirical level of theory.