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Authors response for "Acceleration of Catalyst Discovery with Easy, Fast, and Reproducible Computational Alchemy "
[post]

John A Keith, Charles Griego, John R Kitchin

2020
unpublished

Reviewer 1's original text is given in bold while our responses are in plain text. 1. My main question is whether the authors have seen any kind of finite-size effect on the alchemical potential due to the minimal cell employed in this study. Due to the coulombic form of the alchemical potential, it appears unlikely that there is no such effect, but potentially it is a quite systematic contribution for all target systems considered. While the errors might be attributed as due to finite-size
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... to finite-size effects, our group has considered smaller and larger unit cells to describe adsorbates bound to the surface with different coverages. We find that first order APDFT is generally more accurate when alchemical derivatives of or near the transmuted atoms are low, and less accurate when alchemical derivatives of or near the transmuted atoms are high. For small unit cells with high adsorbate coverages, errors are usually high, but for large unit cells they are still high if the transmuted atom is near the binding site of the adsorbate. For now, we prefer to think of errors in terms of the magnitude of the alchemical derivatives near the transmuted sites, though considering this as a finite-size effect may not be incorrect. 2. The authors state "Computational alchemy is a perturbation theory approximation". It might be warranted to rather emphasise in the article that it is the Taylor series truncation that renders it an approximation. Under the supposition that the Taylor series converges, in fact the expansion should be exact. Admittedly, not all of the terms (e.g. basis function changes in the direction of the alchemical change) are typically taken into account explicitly, but only if the perturbation approach is exact in the first place, computational alchemy can expect to have the predictive power that is required for the materials design applications outlined in this work. This is an excellent point, and we have revised the text here as well as changed most mentions of "computational alchemy" to be "first order APDFT" as the latter is more precise along these terms. We have also changed the text explaining Eq. 4 to better clarify. 3. Similarly, when the authors discuss the charge neutrality of the alchemical change, it might be important to highlight that the theory does not require the changes in nuclear charges to be strictly compensated. In this particular application however, the change should be neutral as otherwise the total surface charge density of the interface becomes unphysically large. We have revised our text to highlight this point.

doi:10.22541/au.159198696.62443043
fatcat:nrizjfuvmbg2dnqhoxlsiymcbq