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arXiv · 2509.23498

WTMAD-4: A Fair Weighting Scheme for GMTKN55

Kyle R. Bryenton·Erin R. Johnson
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Abstract

The GMTKN55 data set is a collection of standard benchmarks used in molecular quantum chemistry that spans small- and large-molecule thermochemistry, reaction barriers, and non-covalent interactions. Herein, we identify a flaw in the weighted mean absolute deviation (WTMAD) definitions commonly used to quantify performance of various electronic-structure methods for the GMTKN55 set, which under-weight some of its component benchmarks by orders of magnitude. A new WTMAD-4 metric is proposed, based on typical errors observed for a set of ten minimally empirical dispersion-corrected density-functional approximations (DFAs), ensuring fair treatment across all benchmarks. The performance of 115 DFAs is then reassessed using WTMAD-4 and we highlight a literature example where a DFA parametrised by minimising WTMAD-2 underperforms for benchmarks marginalised by that metric.

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Kyle R. Bryenton, Erin R. Johnson. 2025-09-27. WTMAD-4: A Fair Weighting Scheme for GMTKN55. https://doi.org/10.1039/d5cp03741g

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