Second derivatives for approximate spin projection methods

Thompson, Lee M.; Hratchian, Hrant P.

doi:10.1063/1.4907269

Cited by 20 publications

(33 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…60 Our group has expanded the AP model to include analytical first and second derivatives. 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: 96%

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

Section: Approximate Projection Methodsmentioning

confidence: 96%

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

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

“…28 Calculations using the AP model employed local implementations of analytic first-and second-derivative programs. 11,26,27 The examination of J-coupling calculations used the test set reported by Peralta and Rudra. 29,30 Calculations have been carried out using five different functionals: B3LYP, 31,32 LC-ωPBE, 33,34 CAM-B3LYP, 35 B3PW91 36 and ωB97XD.…”

Section: Computational Detailsmentioning

confidence: 99%

“…25 It seems reasonable to expect that projection may alter the PES and yield different minimum energy structures than these previous reports. To support such studies, our group has extended the use of AP by developing and implementing efficient first and second derivatives, 26,27 making geometry optimization and force constant evaluations on AP-corrected PESs practical.…”

Section: Introductionmentioning

confidence: 99%

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

Sheng¹,

Thompson²,

Hratchian

2019

Preprint

Self Cite

View full text Add to dashboard Cite

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of $J$-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Projection model provides an affordable and practical approach for effectively correcting spin-contamination errors in such calculations.

show abstract

Second derivatives for approximate spin projection methods

Cited by 20 publications

References 29 publications

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

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

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

Contact Info

Product

Resources

About