Barriers to predictive high-throughput screening for spin-crossover

Current spin-crossover (SCO) energy calculations depend on nearly artisanal skill in picking quantum mechanical approximations and computational methods. That is incompatible with automated (work-flow-driven) screening. An acceptable methodology must be mechanically sound, yield both basic structure property values, accurate ?EHL without steering or tuning. Cost vs. accuracy causes focus density functional theory (DFT). We show by a near-exhaustive study of schemes for calculating the molecular high-low spin difference, ?EHL, that presently there no combination constraint-based, non-empirical approximation (DFA) set well-defined semi-empirical corrections to it adequate such protocol. Somewhat successful hybrid DFA are too costly high-throughput screening condensed phases. Lower-cost alternatives combine generalized gradient (GGA) Hubbard-U correction (DFT + U). But we neither U=0 nor any currently available unsteered U calculation gives decent value [Mn(taa)] also degrading predictions. Moving SCAN meta-GGA does not solve problem. The revised-restored (r2SCAN) together its deorbitalized version r2SCAN-L give improved but wholly satisfactory results. document diagnose several non-obvious technical procedural sensitivities inter-code differences. In addition being formidable challenge development, lack delineate major impediment progress development materials spintronics.