Geometry optimization using local-density functional methods: Numerical aspects

Jones, R. S.; Mintmire, J. W.; Dunlap, Brett I.

doi:10.1002/qua.560340813

Cited by 28 publications

(11 citation statements)

References 13 publications

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“…While this has been known for decades, 28,[31][32][33] some users are not aware of this shortcoming because many quantum chemistry codes automatically reorient molecules such that the principle axes are aligned with the Cartesian axes (the so-called 'standard orientation'). Luckily, this lack of rotational invariance has negligible impact on relative electronic energies, at least for small systems and some DFT functionals (vide infra).…”

Section: Resultsmentioning

confidence: 99%

Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

Bootsma¹,

Wheeler²

2019

Preprint

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<div>Density functional theory (DFT) has emerged as a powerful tool for analyzing organic and organometallic systems and proved remarkably accurate in computing the small free energy differences that underpin many chemical phenomena (e.g. regio- and stereoselective reactions). We show that the lack of rotational invariance of popular DFT integration grids reveals large uncertainties in computed free energies for isomerizations, torsional barriers, and regio- and stereoselective reactions. The result is that predictions based on DFT-computed free energies for many systems can change qualitatively depending on molecular orientation. For example, for a metal-free propargylation of benzaldehyde, predicted enantioselectivities based on B97-D/def2-TZVP free energies using the popular (75,302) integration grid can vary from 62:38 to 99:1 by simply rotating the transition state structures. Relative free energies for the regiocontrolling transition state structures for an Ir-catalyzed C–H functionalization reaction computed using M06/6-31G(d,p)/LANL2DZ and the same grid can vary by more than 5 kcal/mol, resulting in predicted regioselectivities that range anywhere from 14:86 to >99:1. Errors of these magnitudes occur for different functionals and basis sets, are widespread among modern applications of DFT, and can be reduced by using much denser integration grids than commonly employed.</div>

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Section: Resultsmentioning

confidence: 99%

Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

Bootsma¹,

Wheeler²

2019

Preprint

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show abstract

“…While this has been known for decades, 30,[33][34][35] some users are not aware of this shortcoming because many quantum chemistry codes automatically reorient molecules such that the principle axes are aligned with the Cartesian axes (the so-called 'standard orientation'). Luckily, this lack of rotational invariance has negligible impact on relative electronic energies, at least for small systems and some DFT functionals (vide infra).…”

Section: Resultsmentioning

confidence: 99%

“…Even with the very large (174,975) grid the ΔΔG ‡ values for reaction 5 can vary by more than 1 kcal mol -1 . The lack of rotational invariance of DFT energies, gradients, and vibrational frequencies is widely acknowledged, [33][34][35] and documentation for many quantum chemistry packages include caveats regarding the sensitivity of vibrational frequencies to integration grids. For instance, starting with Gaussian98, a (99,590) grid has been recommended for computing 'very low frequency modes.'…”

Section: Resultsmentioning

confidence: 99%

Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

Bootsma¹,

Wheeler²

2019

Preprint

View full text Add to dashboard Cite

Density functional theory (DFT) has emerged as a powerful tool for analyzing (bio-)organic and organometallic systems and proved remarkably accurate in computing the small free energy differences that underpin many chemical phenomena (e.g. regio- and stereoselective reactions). We show that the lack of rotational invariance of popular DFT integration grids reveals large uncertainties in computed free energies for some isomerizations, torsional barriers, and regio- and stereoselective reactions. The result is that predictions based on DFT-computed free energies for systems with very low-frequency vibrational modes can change qualitatively depending on molecular orientation. For example, for a metal-free propargylation of benzaldehyde, predicted enantioselectivities based on B97-D/def2-TZVP free energies using a popular pruned (75,302) integration grid can vary from 62:38 to 99:1 by simply rotating the transition state structures. Relative free energies for the regiocontrolling transition state structures for an Ir-catalyzed C–H functionalization reaction computed using M06/6-31G(d,p)/LANL2DZ and the same grid can vary by more than 5 kcal/mol, resulting in predicted regioselectivities that range anywhere from 14:86 to >99:1. Errors of these magnitudes occur for different functionals and basis sets, are potentially widespread among modern applications of DFT, and can be reduced by using much denser integration grids than commonly employed.<br>

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“…Gaussian atom-centered basis functions are used to expand the Kohn-Sham orbitals and to fit the associated density and XC potential. The XC energy is evaluated by numerical integration on a grid very similar to that of Beckel I with a random orientation of each quasispherical shell of angular points, as suggested by Jones et al 12 Calculations have been made using the LSD potential ofVosko, Wilk, and Nusair l3 (VWN) and also with the nonlocal, gradient corrected, functional of Perdew and Wang (PW). 14 In some calculations the XC potential of PW was used self-consistently as described by Mlynarski and Salahub l5 (" PW" calculations) whereas in other cases we solved the seIf-consistent-fieId (SCF) equations with the VWN potential and then computed the energy with the PW functional ("PW /VWN" calculations).…”

Section: Methodsmentioning

confidence: 99%

Predicted bond energies in peroxides and disulfides by density functional methods

Fournier

DePristo

1992

The Journal of Chemical Physics

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We have performed self-consistent linear combination of Gaussian-type orbitals-density functional calculations for the molecules YY, RY, RYY, RYR′, RYYR, and RYYR′ with Y=O,S and R,R′=H,CH3. The structures were optimized within the local spin density approximation while the Y–Y, Y–C, and Y–H bond dissociation energies (BDE) were calculated with both a local exchange-correlation energy functional and a gradient corrected functional. Comparison of results obtained with the local and gradient corrected exchange-correlation functionals provides more experience on the successes and failures of gradient corrections. Trends in BDEs and the nature of bonding in oxygen and sulfur containing analog molecules are analyzed on the basis of two observations: (1) the O atom is more electronegative than S, C, and H atoms; (2) a S atom can have a valency larger than two and has a greater ability for multiple bonding than oxygen. Finally, comparison with a number of experimental results suggest that the C–S BDE in CH3S, the S–S BDE in CH3SSCH3, and the enthalpy of formation of CH3S should be reexamined.

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Geometry optimization using local-density functional methods: Numerical aspects

Cited by 28 publications

References 13 publications

Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

Predicted bond energies in peroxides and disulfides by density functional methods

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