Chalcopyrite semiconductors are of considerable interest for application as absorber layers in thin-film photovoltaic cells. When growing films of these compounds, however, they are often found to contain CuAu-like domains, a metastable phase of chalcopyrite. It has been reported that for CuInS₂, the presence of the CuAu-like phase improves the short circuit current of the chalcopyrite-based photovoltaic cell. We investigate the thermodynamic stability of both phases for a selected list of I–III–VI₂ materials using a first-principles density functional theory approach. For the CuIn–VI₂ compounds, the difference in formation energy between the chalcopyrite and CuAu-like phase is found to be close to 2 meV per atom, indicating a high likelihood of the presence of CuAu-like domains. Next, we calculate the spectroscopic limited maximum efficiency (SLME) of the CuAu-like phase and compare the results with those of the corresponding chalcopyrite phase. We identify several candidates with a high efficiency, such as CuAu-like CuInS₂, for which we obtain an SLME of 29% at a thickness of 500 nm. We observe that the SLME can have values above the Shockley–Queisser (SQ) limit, and show that this can occur because the SQ limit assumes the absorptivity to be a step function, thus overestimating the radiative recombination in the detailed balance approach. This means that it is possible to find higher theoretical efficiencies within this framework simply by calculating the J–V characteristic with an absorption spectrum. Finally, we expand our SLME analysis to indirect band gap absorbers by studying silicon, and find that the SLME quickly overestimates the reverse saturation current of indirect band gap materials, drastically lowering their calculated efficiency.

We perform a high-throughput computational search for novel phonon-mediated superconductors, starting from the Materials Cloud three-dimensional structure database of experimentally known inorganic stoichiometric compounds. We first compute the Allen-Dynes critical temperature ( T c AD ) for 4533 nonmagnetic metals using a direct and progressively finer sampling of the electron-phonon couplings. For the candidates with the largest T c AD value, we use automated Wannierizations and electron-phonon interpolations to obtain a high-quality data set for the most promising 250 dynamically stable structures, for which we calculate spectral functions, superconducting band gaps, and isotropic Migdal-Eliashberg critical temperatures. For 140 of these, we also provide anisotropic Migdal-Eliashberg superconducting gaps and critical temperatures. The approach is remarkably successful in finding known superconductors and we find 24 unknown ones with a predicted anisotropic T c value above 10 K. Among them, we identify a possible double-gap superconductor ( p -doped Ba B 2 ), a nonmagnetic half-Heusler Zr Ru Sb , and the perovskite Ta Ru 3 C , all exhibiting significant T c values. Finally, we introduce a sensitivity analysis to estimate the robustness of the predictions.

The Python Workflow Definition (PWD) is a workflow exchange format to share workflows between Python-based workflow management systems, currently AiiDA, jobflow, and pyiron.

When slow ions incident on a surface are neutralized, the excess potential energy is passed on to an electron inside the surface, leading to emission of secondary electrons. The microscopic description of this process, as well as the calculation of the secondary electron yield, is a challenging problem due to its complexity as well as its sensitivity to surface properties. One of the first quantitative descriptions was articulated in the 1950s by Hagstrum, who based his calculation on a parametrization of the density of states of the material. In this paper, we present a model for calculating the secondary electron yield, derived from Hagstrum's initial approach. We use first-principles density functional theory calculations to acquire the necessary input and introduce the concept of electron cascades to Hagstrum's model in order to improve the calculated spectra, as well as remove its reliance on fitting parameters. We apply our model to ${\mathrm{He}}^{+}$ and ${\mathrm{Ne}}^{+}$ ions incident on $\mathrm{Ge}\left(111\right)$ and $\mathrm{Si}\left(111\right)$ and obtain yield spectra that match closely to the experimental results of Hagstrum.