Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model To Improve Density Functional Calculations

Sheng, Xianghai; Thompson, Lee M.; Hratchian, Hrant P.

doi:10.1021/acs.jctc.9b00387

Cited by 11 publications

(19 citation statements)

References 63 publications

(123 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…MECP calculations must be carried out with the aid of spin-projection schemes that self-consistently identify spinpure solutions at every step. 58 In addition, a comparison of kinetic isotope effects (for both OXO and RAD) with experiment is necessary to confirm mechanistic conclusions. These tasks constitute future work in our group.…”

Section: Discussionmentioning

confidence: 99%

A computational mechanistic study of CH hydroxylation with mononuclear copper-oxygen complexes

Lan

Toney

Sharada

2022

Preprint

View full text Add to dashboard Cite

We present a computational study of methane hydroxylation by oxygen-bound monocopper complexes with the twin goals of resolving the active site identity and preferred mechanism of CH activation. Oxyl ([Cu(II)O(Im)3]+) and superoxo ([Cu(II)OO(Im)3]+) monocopper centers coordinated to three imidazole N-donors are investigated. Constrained density functional theory (CDFT) is necessary to overcome delocalization errors inherent to DFT and generate catalyst geometries with physically meaningful charge and spin at the active site. A comparison of ground-state triplet and excited-state singlet potential energy profiles for CH hydroxylation shows that oxyl is the more likely active site. For oxyl, spin crossing from the triplet to singlet potential energy surface yields a lower energy hydroxylation pathway when compared to the pure triplet surface. The calculation of minimum energy crossing points is an essential next step towards determining whether CH hydroxylation proceeds via a two-step radical or single-step oxo-insertion mechanism.

show abstract

Section: Discussionmentioning

confidence: 99%

A computational mechanistic study of CH hydroxylation with mononuclear copper-oxygen complexes

Lan

Toney

Sharada

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…75,76 In fact, several works have shown the effectiveness of this model and demonstrated the condition for which this model is suitable. 64,65,77,78 To carry out AP calculations, two converged determinants are required: (…”

Section: Approximate Projection Methodsmentioning

confidence: 99%

“…59 For our purposes, we considered a variation of this scheme, the approximate projection model of Yamaguchi and co-workers, 60 as implemented and extended by our lab. 64,65,[75][76][77][78] Using Eq. 9 and a threshold of 5% spin contamination, 17 systems were identified as being spin contaminated with Δ-DFT and explored using the AP model.…”

Section: Spin Contaminationmentioning

confidence: 99%

“…Among other methods, the proposed approximate projection (AP) technique by Yamaguchi has been successfully used in correcting spin-contamination errors. [60][61][62][63][64][65] In this work, the usage of the PIMOM framework for geometry optimization and frequency calculation of excited-states molecules is explored. An overview of the method and computational details are given in Section 2.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Good Vibrations: Calculating Excited State Frequencies Using Ground State Self-Consistent Field Models

Taka

Corzo

Pribram‐Jones

et al. 2021

Preprint

View full text Add to dashboard Cite

△SCF methods have proven to be reliable computational tools for the assignment and interpretation of photoelectron spectra of isolated molecules. These results have increased the interest in △SCF techniques for electronic excited states based on improved algorithms that prevent convergence to ground states. In this work, one of these △SCF improved algorithms is studied to demonstrate its ability to explore the molecular properties for excited states. Results from △SCF calculations for a set of representative molecules are compared with results obtained using time-dependent density functional theory and single substitution configuration interaction method. For the △SCF calculations, the efficacy of a spin-purification technique is explored to remedy some of the spin-contamination presented in some of the SCF solutions. The obtained results suggest that the proposed projection-based SCF scheme, in many cases, alleviates the spin--contamination present in the SCF single determinants, and provides a computational alternative for the efficient exploration of the vibrational properties of excited states molecules.

show abstract

“…70 Preliminary calculations following protocols developed in one of our labs and considering approximate (spin) projection models to remedy impacted energies, forces, and force constants suggested that spin-contamination should not negatively impact the PIMOM based spectral simulations reported in this study. [71][72][73][74][75][76][77][78] Molecular geometries for ground and excited states were optimized using standard methods, 79 and the reported PES minima were verified using analytical second-derivative calculations. 80,81 The methylene blue ground state S 0 optimized structure is of C 2v symmetry for both B3LYP and CAM-B3LYP.…”

Section: Condon Vibronic Spectral Calculationsmentioning

confidence: 99%

Comparison of Linear Response Theory, Projected Initial Maximum Overlap Method, and Molecular Dynamics Based Vibronic Spectra: The Case of Methylene Blue

Taka

Gowland

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Simulation of optical spectra is essential to molecular characterization and, in many cases, critical for interpreting experimental spectra. The most common method for simulating vibronic absorption spectra relies on the geometry optimization and computation of normal modes for ground and excited states. In this report, we show that utilization of such a procedure within an adiabatic linear response theory framework may lead to state mixings and a breakdown of the Born-Oppenheimer approximation, resulting in a poor description of absorption spectra. In contrast, computing excited states via a self-consistent eld method in conjunction with a maximum overlap model produces states that are not subject to such mixings. We show that this latter method produces vibronic spectra much more aligned with vertical excitation procedures, such as those computed from a vertical gradient or molecular dynamics trajectory-based approach. For the methylene blue chromophore, we compare vibronic absorption spectra computed with: an adiabatic Hessian approach with linear response theory optimized structures and normal modes, a vertical gradient procedure, the Hessian and normal modes of maximum overlap method optimized structures, and excitation energy time correlation functions generated from a molecular dynamics trajectory. Due to mixing between the bright S1 and dark S2 surfaces near the S1 minimum, computing the adiabatic Hessian with linear response theory time-dependent density functional theory with the B3LYP density functional predicts a large vibronic shoulder for the absorption spectrum that is not present for any of the other methods. Spectral densities are analyzed and we compare the behavior of the key normal mode that in linear response theory strongly couples to the optical excitation while showing S1/ S2 state mixings. Overall, our study provides a note of caution in computing vibronic spectra using the excited state adiabatic Hessian of linear response theory optimized structures and also showcases three alternatives that are not as subject to adiabatic state mixing effects.

show abstract

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model To Improve Density Functional Calculations

Cited by 11 publications

References 63 publications

A computational mechanistic study of CH hydroxylation with mononuclear copper-oxygen complexes

A computational mechanistic study of CH hydroxylation with mononuclear copper-oxygen complexes

Good Vibrations: Calculating Excited State Frequencies Using Ground State Self-Consistent Field Models

Comparison of Linear Response Theory, Projected Initial Maximum Overlap Method, and Molecular Dynamics Based Vibronic Spectra: The Case of Methylene Blue

Contact Info

Product

Resources

About