Abstract
AbstractWhile alloying is a powerful handle for materials engineering, it is an ongoing challenge to navigate the large and complex parameter space of these materials. This applies in particular for thermoelectrics and even more so clathrates. Here, a combination of density functional theory calculations, alloy cluster expansions, Monte Carlo simulations, and Boltzmann transport theory calculations is used to identify compositions that yield high power factors in the pseudo‐ternary clathrates Ba8AlxGayGe46−x−y and Ba8GaxGeySi46−x−y, while accounting for weight and raw material costs. The results show how a cost‐efficient performance can be achieved by reducing the number of Al and Ga atoms per unit cell, while compensating the resulting increase in the carrier concentration via an extrinsic dopant. The approach used in this study is transferable and can be a useful tool for mapping the thermodynamic and transport properties of other multinary systems.
Highlights
While alloying is a powerful handle for materials engineering, it is an ongoing challenge to navigate the large and complex parameter space of these materials
Ga16−xGe30,[19] we know that the electronic transport properties are strongly influenced by chemical ordering, which is a direct consequence of the unique structural motifs of clathrates
According to the Zintl concept, it is expected that the guest atoms are not directly bonded to the Computationally driven strategies have been demonstrated to host framework, but rather donate their electrons to the latter accelerate the development of thermoelectrics[1,2,3,4,5,6,7,8,9,10] as well as other so as to ensure that all atoms have a full octet in their valence functional materials.[11,12,13]
Summary
Based on a thorough testing of three alternative fitting methods, we decided to use recursive feature elimination (RFE) with ordinary least squares (OLS) to train the CEs, since it results in low cross-validation (CV) root-mean-square error (RMSE) scores for relatively few non-zero parameters (Figure S2, Supporting Information). As a further measure of the performance of the CEs we calculated the predictive errors for all target energies, which fall between ±2 meV atom−1 Both the Ba8AlxGayGe46−x−y (Figure 1b and Ba8GaxGeySi46−x−y (Figure 1c CEs are comparable in performance to those that we have previously reported for Ba8GaxGe46−x, Ba8GaxSi46−x, Ba8AlxGe46−x, and Ba8AlxSi46−x.[15] To further validate the models, we compared the SOFs obtained from sampling CEs ensembles, for both pseudo-ternary and pseudo-binary clathrates, with experimental data[34,35,57,58,59,60,61,62,63,64,65,66,67] (see Note S5, Supporting Information and Figure S4, Supporting Information). Good agreement is obtained with respect www.advelectronicmat.de to the measured data as well as between the pseudo-ternary and pseudo-binary CEs
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