Catalysis by Ab-initio Metadynamics in Parallel
|Scientific Discipline||Materials Science, Quantum Chemistry|
|Principal Investigator(s)||Prof. Dr. Michele Parrinello|
|Leading Institution||ETH Zurich, Switzerland|
|DEISA Home Site||RZG|
There is an ongoing discussion concerning the processes which contributed significantly to the formation of life on the early Earth. Several possible scenarios and theories have been suggested, however, their proof often requires to perform experiments under extreme conditions where usually many complex reactions are taking place, instantaneously. In this context, ammonia formation is considered as an essential step in the formation of a reducing environment favorable for the production of organic precursors to life. There is experimental evidence that pyrite (FeS$_2$) exhibits high catalytic activity under hydrothermal conditions as they were present in the deep sea near volcanos at the interfaces between extremely hot and pressurized water and iron-sulfur minerals. In particular, pyrite has been suggested as the key catalyst in the synthesis of prebiotic molecules under these anoxic conditions in the early history of the Earth.
Figure 1. The results of the all-electron and pseudopotential calculations for bulk pyrite using different Gaussian basis sets.
The goal of the project was to achieve a better understanding of the pyrite surface and its chemistry by means of ab-initio calculations. To this end, we studied the properties of the sulfur monomeric defects on the pyrite surface by considering two possible monomeric species, which can be obtained by a heterolytic breaking of the surface sulfur dimers. A spin triplet state turned out to be the ground state configuration for this system. This state is also stable against the wetting of the surface. Moreover, the formation of the sulfur defect site is accompanied by a change in the oxidation state of the iron from Fe(II) to Fe(IV). This observation is confirmed by a good agreement between the calculated sulfur core level shifts of different sulfur species and the experimental photoemission spectra.
Moreover, a new method was developed and implemented into the CP2K program package, which allows to perform routinely ab-initio molecular dynamics simulation of nanosecond time scale and thus making a new class of problems accessible to ab-initio simulations.
Finally, a web application plug-in for the CP2K program package has been implemented in collaboration with the RZ Garching, which will facilitate the use of CP2K within the DEISA computing infrastructure.
Figure 2.Simulation of the nitrate reduction using an enlarged model system