2 research outputs found
Spectroscopic Characterization of Rocksalt-Type Aluminum Nitride
Starting from nanocrystalline and
submicron wurtzite-aluminum nitride (w-AlN) powder rocksalt structure
(rs-AlN) samples were synthesized by two different methods of shock
wave recovery experiments. The resulting samples contained up to 86%
rs-AlN, stable at room temperature, giving for the first time the
possibility to comprehensively characterize the material by powder
X-ray diffraction, Fourier transform infrared (IR), Raman, and <sup>27</sup>Al NMR spectroscopy. Raman and IR modes were calculated by
density functional theory, allowing for the interpretation of the
respective experimental spectra. By <sup>27</sup>Al NMR the chemical
shift of rs-AlN was determined, and the quadrupolar coupling constant
was estimated
Automating the Optimization of Catalytic Reaction Mechanism Parameters Using Basin-Hopping: A Proof of Concept
Parameter estimation is a crucial step for successful
microkinetic
modeling in catalysis. However, the large number of parameters to
be optimized in order to match the experimental data is a bottleneck.
In this regard, the global optimization algorithm Basin-Hopping is
utilized to automate the typically time-extensive and error-prone
task of manual fitting of kinetic parameters for a heterogeneous catalytic
system. The stochastic approach of the Basin-Hopping algorithm to
explore the kinetic parameter solution space coupled with local search
methods makes it possible to screen the high-dimensional space for
an optimal set of kinetic parameters giving the least residual between
the simulated and the experimentally measured catalytic performance
data. Our approach also ensures that only thermodynamically consistent
solution candidates are explored at each optimization step. We utilize
two example case studies in heterogeneous catalysis, namely, methane
oxidation over a palladium catalyst and carbon monoxide methanation
over a nickel catalyst, with corresponding detailed kinetic models
to illustrate the applicability of the algorithm to efficiently fine-tune
detailed kinetic models