Engineering topics
Publications and source records attributed to Rossomme, Elliot.
We investigate the transferability of NLCC pseudopotentials (PPs) using the GTH protocol with various functionals (GGA, meta-GGA, hybrid), exploring their effects on thermochemical and non-thermochemical properties.
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The pseudopotential (PP) approximation is one of the most common techniques in computational chemistry. Despite its long history, the development of custom PPs has not tracked with the explosion of different density functional approximations (DFAs). As a result, the use of PPs with exchange/correlation models for which they were not developed is widespread, although this practice is known to be theoretically unsound. The extent of PP inconsistency errors (PPIEs) associated with this practice has not been systematically explored across the types of energy differences commonly evaluated in chemical applications. Here, we evaluate PPIEs for a number of PPs and DFAs across 196 chemically relevant systems of both transition-metal and main-group elements, as represented by the W4-11, TMC34, and S22 data sets. Near the complete basis set limit, these PPs are found to cleanly approach all-electron (AE) results for noncovalent interactions but introduce root-mean-squared errors (RMSEs) upwards of 15 kcal mol –1 into predictions of covalent bond energies for a number of popular DFAs. We achieve significant improvements through the use of empirical atom- and DFA-specific PP corrections, indicating considerable systematicity of the PPIEs. The results of this work have implications for chemical modeling in both molecular contexts and for DFA design, which we discuss.
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Despite the widespread use of copper catalysis for the formation of C–C bonds, debate about the mechanism persists. Reductive elimination from Cu(III) is often invoked as a key step, yet examples of its direct observation from isolable complexes remain limited to only a few examples. In this work, we demonstrate that incorporation of bulky mesityl (Mes) groups into the α-positions of a phenanthrene-appended zirconacyclopenta- diene, Cp 2 Zr(2,5-Mes 2 -phenanthro[9,10]C 4 ), enables efficient oxidative transmetalation to the corresponding, formal Cu(III) metallacyclopentadiene dimer. The dimer was quantitatively converted to a structurally analogous anionic monomer [ n Bu 4 N]- {Cl 2 Cu(2,5-Mes 2 -phenanthro[9,10]C 4 )} upon treatment with [ n Bu 4 N][Cl]. Both metallacycles undergo quantitative reductive elimination upon heating to generate phenanthrocyclobutadiene and a Cu(I) species. Due to the steric protection provided by the mesityl groups, this cyclobutadiene was isolated and thoroughly characterized to reveal antiaromaticity comparable to that of free cyclobutadiene, which imbues it with a small highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap of 1.85 eV and accessible reduced and oxidized electronic states.
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Density Functional Theory (DFT) is currently the most tractable choice of theoretical model used to understand the mechanistic pathways for electrocatalytic processes such as CO 2 or CO reduction. In this work, we assess the performance of two DFT functionals designed specifically to describe surface interactions, RTPSS and RPBE, as well as two popular meta-GGA functionals, SCAN and B97M-rV, that have not been a priori optimized for better interfacial properties. We assess all four functionals against available experimental data for prediction of bulk and bare surface properties on four electrocatalytically relevant metals, Au, Ag, Cu, and Pt, and for binding CO to surfaces of these metals. To partially mitigate issues such as thermal and anharmonic corrections associated with comparing computations with experiments, molecular benchmarks against high level quantum chemistry are reported for CO complexes with Au, Ag, Cu and Pt atoms, as well as the CO–water complex and the water dimer. Overall, we find that the surface modified RPBE functional performs reliably for many of the benchmarks examined here, and the meta-GGA functionals also show promising results. Specifically B97M-rV predicts the correct site preference for CO binding on Ag and Au (the only functional tested here to do so), while RTPSS performs well for surface relaxations and binding of CO on Pt and Cu.