K. Lejaeghere

Ranking the stars: A refined Pareto approach to computational materials design

K. Lejaeghere, S. Cottenier, V. Van Speybroeck
Physical Review Letters
111 (7), 075501


We propose a procedure to rank the most interesting solutions from high-throughput materials design studies. Such a tool is becoming indispensable due to the growing size of computational screening studies and the large number of criteria involved in realistic materials design. As a proof of principle, the binary tungsten alloys are screened for both large-weight and high-impact materials, as well as for fusion reactor applications. Moreover, the concept is generally applicable to any design problem where multiple competing criteria have to be optimized.

Open Access version available at UGent repository

Error estimates for solid-state density-functional theory predictions: an overview by means of the ground-state elemental crystals

K. Lejaeghere, V. Van Speybroeck, G. Van Oost, S. Cottenier
Critical Reviews in Solid State and Materials Sciences
39 (1), 1-24


Predictions of observable properties by density-functional theory calculations (DFT) are used increasingly often by experimental condensed-matter physicists and materials engineers as data. These predictions are used to analyze recent measurements, or to plan future experiments in a rational way. Increasingly more experimental scientists in these fields therefore face the natural question: what is the expected error for such a first-principles prediction? Information and experience about this question is implicitly available in the computational community, scattered over two decades of literature. The present review aims to summarize and quantify this implicit knowledge. This eventually leads to a practical protocol that allows any scientist -- experimental or theoretical -- to determine justifiable error estimates for many basic property predictions, without having to perform additional DFT calculations.

A central role is played by a large and diverse test set of crystalline solids, containing all ground-state elemental crystals (except most lanthanides). For several properties of each crystal, the difference between DFT results and experimental values is assessed. We discuss trends in these deviations and review explanations suggested in the literature.

A prerequisite for such an error analysis is that different implementations of the same first-principles formalism provide the same predictions. Therefore, the reproducibility of predictions across several mainstream methods and codes is discussed too. A quality factor Delta expresses the spread in predictions from two distinct DFT implementations by a single number. To compare the PAW method to the highly accurate APW+lo approach, a code assessment of VASP and GPAW (PAW) with respect to WIEN2k (APW+lo) yields Delta-values of 1.8 and 3.3 meV/atom, respectively. In both cases the PAW potentials recommended by the respective codes have been used. These differences are an order of magnitude smaller than the typical difference with experiment, and therefore predictions by APW+lo and PAW are for practical purposes identical.

Assessment of a low-cost protocol for an ab initio based prediction of the mixing enthalpy at elevated temperatures: The Fe-Mo system

K. Lejaeghere, S. Cottenier, S. Claessens, M. Waroquier, V. Van Speybroeck
Physical Review B
83, 184201


We demonstrate how a limited number of ab initio calculations in combination with a simple Debye model can predict a concentration- and temperature-dependent mixing enthalpy for a binary system. Fe-Mo is taken as a test case, and our predictions are compared with phase diagram information and a recently measured heat of solution for Mo in Fe. Crystallographic and magnetic information is calculated for the λ and μ intermetallic phases in the Fe-Mo phase diagram as well. The present methodology can be useful for making a quick survey of mixing enthalpies in a large set of binary systems, in particular in the dilute concentration ranges where tabulated data are often lacking and where calphad-style modeling is less reliable.

Open Access version available at UGent repository

Stabilizing the perovskite phase of cesium lead iodide thin films via interfacial strains


Conference / event / venue 

5th International Conference on Perovskite Solar Cells and Optoelectronics (PSCO19)
Lausanne, Switzerland
Monday, 30 September, 2019 to Wednesday, 2 October, 2019


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