arXiv subjects

Romain Claes

Publications and source records attributed to Romain Claes.

4 recordsLinked to original sources

arXiv2026

Revealing low-energy surfaces of multinary compounds by controlling surface coordination environments

When modeling surfaces of multinary compounds, conventional cleavage planes often cut through strongly bonded polyhedra, resulting in unphysical surface energies. Here, we introduce SALAMI (Symmetric Atomic Layers for Arbitrary Multinary Interfaces), a Python package that generates symmetric, charge-neutral, dipole-free, and low-energy slab models for multinary compounds. SALAMI performs combinatorial searches to selectively remove surface atoms and generate corrugated terminations that preserve optimal coordination environments. We applied this workflow to all symmetrically inequivalent crystallographic orientations with Miller indices up to 2 for two prototypical structures: the solid-state electrolyte Li3PS4 and the transparent conducting oxide ZnSb2O6. Density functional theory calculations reveal that Li3PS4 must preserve all PS4 units to achieve the minimum surface energy. For ZnSb2O6, low-energy surfaces are achieved by partial undercoordination of surface Sb atoms to SbO5 or SbO4 from the bulk SbO6, depending on the surface orientations. Compared to surface models generated with unconstrained coordination, applying constraints to achieve optimal local coordination environments significantly lowers surface energies, shrinking the volume of the predicted Wulff shape by approximately 20%. Our results demonstrate that meticulous control of local coordination environments is necessary for accurately predicting the surface energetics of multinary compounds.

cond-mat.mtrl-sci↗

arXiv2024

Assessing carrier mobility, dopability, and defect tolerance in the chalcogenide perovskite BaZrS$_3$

The chalcogenide perovskite BaZrS$_3$ has attracted much attention as a promising solar absorber for thin-film photovoltaics. Here, we use first-principles calculations to evaluate its carrier transport and defect properties. We find that BaZrS$_3$ has a phonon-limited electron mobility of 37 cm$^2$/Vs comparable to that in halide perovskites but lower hole mobility of 11 cm$^2$/Vs. The defect computations indicate that BaZrS$_3$ is intrinsically n-type due to shallow sulfur vacancies, but that strong compensation by sulfur vacancies will prevent attempts to make it p-type. We also establish that BaZrS$_3$ shows some degree of defect tolerance, presenting only few low formation energy, deep intrinsic defects. Among the deep defects, sulfur interstitials are the dominant nonradiative recombination centers but exhibit a moderate capture coefficient. Our work highlights the material's intrinsic limitations in carrier mobility and p-type doping and suggests focusing on suppressing the formation of sulfur interstitials to reach longer carrier lifetime.

cond-mat.mtrl-sci↗

arXiv2023

Discovery of the Zintl-phosphide BaCd$_{2}$P$_{2}$ as a long carrier lifetime and stable solar absorber

Thin-film photovoltaics offers a path to significantly decarbonize our energy production. Unfortunately, current materials commercialized or under development as thin-film solar cell absorbers are far from optimal as they show either low power conversion efficiency or issues with earth-abundance and stability. Entirely new and disruptive materials platforms are rarely discovered as the search for new solar absorbers is traditionally slow and serendipitous. Here, we use first principles high-throughput screening to accelerate this process. We identify new solar absorbers among known inorganic compounds using considerations on band gap, carrier transport, optical absorption but also on intrinsic defects which can strongly limit the carrier lifetime and ultimately the solar cell efficiency. Screening about 40,000 materials, we discover the Zintl-phosphide BaCd$_{2}$P$_{2}$ as a potential high-efficiency solar absorber. Follow-up experimental work confirms the predicted promises of BaCd$_{2}$P$_{2}$ highlighting an optimal band gap for visible absorption, bright photoluminescence, and long carrier lifetime of up to 30 ns even for unoptimized powder samples. Importantly, BaCd$_{2}$P$_{2}$ does not contain any critical elements and is highly stable in air and water. Our work opens an avenue for a new family of stable, earth-abundant, high-performance Zintl-based solar absorbers. It also demonstrates how recent advances in first principles computation can accelerate the search of photovoltaic materials by combining high-throughput screening with experiment.

cond-mat.mtrl-sci↗

arXiv2022

Assessing the quality of relaxation-time approximations with fully-automated computations of phonon-limited mobilities

The mobility of carriers, as limited by their scattering with phonons, can now routinely be obtained from first-principles electron-phonon coupling calculations. However, so far, most computations have relied on some form of simplification of the linearized Boltzmann transport equation based on either the self-energy, the momentum- or constant relaxation time approximations. Here, we develop a high-throughput infrastructure and an automatic workflow and we compute 69 phonon-limited mobilities in semiconductors. We compare the results resorting to the approximations with the exact iterative solution. We conclude that the approximate values may deviate significantly from the exact ones and are thus not reliable. Given the minimal computational overhead, our work encourages to rely on this exact iterative solution and warns on the possible inaccuracy of earlier results reported using relaxation time approximations.

cond-mat.mtrl-sci↗