<i>In silico</i> prediction of annihilators for triplet–triplet annihilation upconversion <i>via</i> auxiliary-field quantum Monte Carlo

Weber

Coskun

et al. 2022

Preprint

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The accurate ab initio prediction of ionization energies is essential to understanding the electrochemistry of transition metal complexes in both materials science and biological applications. However, such predictions have been complicated by the scarcity of gas-phase experimental data, the relatively large size of the relevant molecules, and the presence of strong electron correlation effects. In this work, we apply all-electron phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) utilizing multi-determinant trial wavefunctions to six metallocene complexes to compare the computed adiabatic and vertical ionization energies to experimental results. We find that ph-AFQMC yields mean averaged errors (MAE) of 1.69±1.02 kcal/mol for the adiabatic energies and 2.85±1.13 kcal/mol for the vertical energies. We also carry out density functional theory (DFT) calculations using a variety of functionals, which yields MAE’s of 3.62 to 6.98 and 3.31 to 9.88 kcal/mol, as well as a localized coupled cluster approach (DLPNO-CCSD(T0)), which has MAEs of 4.96 and 6.08 kcal/mol, respectively. We also test the reliability of DLPNO-CCSD(T0) and DFT on acetylacetonate (acac) complexes for adiabatic energies measured in the same manner experimentally, and find much higher MAE’s, ranging from 4.56 kcal/mol to 10.99 kcal/mol (with a different ordering) for DFT and 6.97 kcal/mol for DLPNO-CCSD(T0). Finally, by utilizing experimental solvation energies, we show that accurate reduction potentials in solution for the metallocene series can be obtained from the AFQMC gas phase results.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Calculation of Metallocene Ionization Potentials via Auxiliary Field Quantum Monte Carlo: Towards Benchmark Quantum Chemistry for Transition Metals

Weber

Coskun

et al. 2022

Preprint

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“…Recent technical advances, including vastly improved efficiency for multideterminantal trial wavefunctions, 23,50 utilization of correlated sampling (CS) in the Monte Carlo protocol to directly compute energy differences, 51 and implementation on GPU hardware, 23,52 has made it feasible to treat significantly larger systems. [53][54][55] These advances have allowed systematic studies of three classes of small transition metal containing species (atoms, diatomic molecules, and tetrahedral, square planar, or octahedral complexes containing simple small molecule ligands) with highly encouraging results.…”

Section: Introductionmentioning

confidence: 99%

“…This is achieved by overcoming significant challenges arising from the greater size and complexity of the metallocene series (as compared to molecules in earlier publications). 23,29,54,55,70 Prior work 54 has demonstrated that it is essential to employ an appropriate multiconfigurational trial wavefunction; calculations based on a single determinant (mainly UHF) trial sometimes yield energy differences comparable to DFT for these systems. Deployment of an appropriate multiconfigurational trial function in the application of the AFQMC approach to transition metal containing systems remains essential if one is aiming at robust, benchmark quality results.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Metallocene Ionization Potentials via Auxiliary Field Quantum Monte Carlo: Towards Benchmark Quantum Chemistry for Transition Metals

Weber²,

Coskun³

et al. 2021

Preprint

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Main Document<div>Supporting Information</div><div>XYZ Coordinates of Structures</div><div><br></div><div><div> An award of computer time was provided by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.</div><div>This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. In particular, we used San Diego Computing Center's Comet resources under grant number TG-CHE190007 and allocation ID COL151.</div><div>The Flatiron Institute is a division of the Simons Foundation.</div></div>

“…Recent technical advances, including vastly improved efficiency for multideterminantal trial wavefunctions, 23,50 utilization of correlated sampling (CS) in the Monte Carlo protocol to directly compute energy differences, 51 and implementation on GPU hardware, 23,52 has made it feasible to treat significantly larger systems. [53][54][55] These advances have allowed systematic studies of three classes of small transition metal containing species (atoms, diatomic molecules, and 4-6 coordinate complexes containing simple small molecule ligands) with highly encouraging results. Atomic ionization potentials, 23 diatomic bond energies, 29 and complex ligand dissociation energies, 54 have all been computed with a MAE of less than 1.5 kcal/mol across relatively large experimental gas phase data sets.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Metallocene Ionization Potentials via Auxiliary Field Quantum Monte Carlo: Towards Benchmark Quantum Chemistry for Transition Metals

Weber

Coskun

et al. 2021

Preprint

Self Cite

The accurate ab initio prediction of ionization energies is essential to understanding the electrochemistry of transition metal complexes in both materials science and biological applications. However, such predictions have been complicated by the scarcity of gas-phase experimental data, the relatively large size of the relevant molecules, and the presence of strong electron correlation effects. In this work, we apply all-electron phase-less auxiliary-field quantum Monte Carlo (ph-AFQMC) utilizing multi-determinant trial wavefunctions to six metallocene complexes to compare the computed adiabaticand vertical ionization energies to experimental results. We find the ph-AFQMC mean averaged errors (MAE) of 1.69±1.02 kcal/mol for the adiabatic energies and 2.85±1.13 kcal/mol for the vertical energies. This significantly outperforms density functional theory (DFT), which has MAE’s of 3.62 to 6.98 and 3.31 to 9.88 kcal/mol, as well as a localized coupled cluster approach (DLPNO-CCSD(T0) with moderate PNO cut-offs), which has MAEs of 4.96 and 6.08 kcal/mol, respectively. We also test the reliability of DLPNO-CCSD(T0) and DFT on acetylacetonate (acac) complexes for adiabatic energies measured in the same manner experimentally, and find higher MAE’s, ranging from 4.56 kcal/mol to 10.99 kcal/mol (with a different ordering) for DFT and 6.97 kcal/mol for DLPNO-CCSD(T0), indicating that none of these approaches can be considered benchmark methods, at least for these complexes. We thus demonstrate that ph-AFQMC should be able to handle metallocene redox chemistry with the advantage of systematically improvable results. By utilizing experimental solvation energies, we show that accurate reduction potentials in solution can be obtained.