Accurate
modeling of heterogeneous catalysis requires the availability
of highly accurate potential energy surfaces. Within density functional
theory, these can—unfortunately—depend heavily on the
exchange-correlation functional. High-level ab initio calculations, on the other hand, are challenging due to the system
size and the metallic character of the metal slab. Here, we present
a quantum Monte Carlo (QMC) study for the benchmark system H2 + Cu(111), focusing on the dissociative chemisorption barrier height.
These computationally extremely challenging ab initio calculations agree to within 1.6 ± 1.0 kcal/mol with a chemically
accurate semiempirical value. Remaining errors, such as time-step
errors and locality errors, are analyzed in detail in order to assess
the reliability of the results. The benchmark studies presented here
are at the cutting edge of what is computationally feasible at the
present time. Illustrating not only the achievable accuracy but also
the challenges arising within QMC in such a calculation, our study
presents a clear picture of where we stand at the moment and which
approaches might allow for even more accurate results in the future.
The incorporation of Si into vapor−liquid−solid GaAs nanowires often leads to p-type doping, whereas it is routinely used as an n-dopant of planar layers. This property limits the applications of GaAs nanowires in electronic and optoelectronic devices. The strong amphoteric behavior of Si in nanowires is not yet fully understood. Here, we present the first attempt to quantify this behavior as a function of the droplet composition and temperature. It is shown that the doping type critically depends on the As/Ga ratio in the droplet. In sharp contrast to vapor−solid growth, the droplet contains very few As atoms, which enhance their reverse transfer from solid to liquid. As a result, Si atoms preferentially replace As in GaAs, leading to p-type doping in nanowires. Hydride vapor phase epitaxy provides the highest As concentrations in the catalyst droplets during their vapor−liquid−solid growth, resulting in n-type dopant behavior of Si. We present experimental data on n-doped Sidoped GaAs nanowires grown by this method and explain the doping within our model. These results give a clear route for obtaining n-type or p-type Si doping in GaAs nanowires and may be extended to other III−V nanowires.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.