Ground State of the (H2O)2+ Radical Cation:  DFT versus Post-Hartree−Fock Methods

Sodupe, Mariona; Bertrán, Juan; Rodrı́guez-Santiago, Luis; Baerends, Evert Jan

doi:10.1021/jp983195u

Cited by 238 publications

(291 citation statements)

References 25 publications

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“…This behavior has been related to a too large spin density delocalization in systems with low coordination numbers (Figure 2), a situation that is overstabilized as a result of a bad cancellation of the self-interaction part by the exchange-correlation functional. 54 Similar trends 50 are observed when including scalar relativistic effects for Cu through the use of the LANLDZ pseudopotential. Moreover, a good description of the second ionization energy of Cu is an important issue for an accurate determination of the Cu 2+ -Aβ/Cu + -Aβ redox potentials.…”

Section: A Electronic Structure Methodssupporting

confidence: 55%

Modeling Cu2+-Aβ complexes from computational approaches

et al. 2015

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Amyloid plaques formation and oxidative stress are two key events in the pathology of the Alzheimer disease (AD), in which metal cations have been shown to play an important role. In particular, the interaction of the redox active Cu2+ metal cation with Aβ has been found to interfere in amyloid aggregation and to lead to reactive oxygen species (ROS). A detailed knowledge of the electronic and molecular structure of Cu2+-Aβ complexes is thus important to get a better understanding of the role of these complexes in the development and progression of the AD disease. The computational treatment of these systems requires a combination of several available computational methodologies, because two fundamental aspects have to be addressed: the metal coordination sphere and the conformation adopted by the peptide upon copper binding. In this paper we review the main computational strategies used to deal with the Cu2+-Aβ coordination and build plausible Cu2+-Aβ models that will afterwards allow determining physicochemical properties of interest, such as their redox potential.

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Section: A Electronic Structure Methodssupporting

confidence: 55%

Modeling Cu2+-Aβ complexes from computational approaches

et al. 2015

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“…Second, on the basis of B3LYP/6-311ϩG* optimized structures, single point calculations have been carried out at the BHLYP/6-311ϩG* ͑with 50% exchange mixing͒ level, because it is comparable to post-Hartree-Fock and is better than the former. 12,27,28 In comparison to the binding energy of 233.2 kcal/mol obtained at the MP2/6-311ϩG(2d,2p)//MP2/6-31G* level in Ref. 15, the binding energy for ͑ϩ2͒-OO at the BHLYP/6-311ϩG*//B3LYP/6-311ϩG* level is 234.4 kcal/ mol ͑see Table VIII͒, only slightly higher than the former.…”

Section: Binding Energymentioning

confidence: 76%

Glycine-Zn+/Zn2+ and their hydrates: On the number of water molecules necessary to stabilize the switterionic glycine-Zn+/Zn2+ over the nonzwitterionic ones

Ai¹,

Han

2003

The Journal of Chemical Physics

101

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Several interaction modes of glycine with one Zn ϩ or Zn 2ϩ and further with one and even two H 2 O molecules in the gas phase are studied at the hybrid three-parameter B3LYP and Hartree-Fock level, respectively. On the basis of these optimized geometries, single point calculations are performed using different theoretical methods and larger basis sets. The calculated results imply that the most stable glycine-Zn ϩ isomer is a five-membered ring with Zn ϩ bound to both amino nitrogen and carbonyl oxygen ͑NO͒ of glycine, and the next most stable glycine-Zn ϩ species is a four-membered ring with Zn ϩ coordinated at both oxygen ends ͑OO͒ of the zwitterionic glycine. The binding energy of the most stable glycine-Zn ϩ is 68.5 kcal/mol calibrated at the BHLYP/6-311ϩG*//6-311ϩG* level. On the contrary with glycine-Zn ϩ isomers, the most stable glycine-Zn 2ϩ species holds the similar coordination mode to that of next most stable glycine-Zn 2ϩ complex, while the next most stable glycine-Zn 2ϩ exhibits the similar coordination mode to that of the most stable glycine-Zn ϩ . The binding strength of these glycine-Zn 2ϩ isomers are all far more than those of their corresponding counterparts of glycine-Zn ϩ isomers, such as the binding energy of the most stable glycine-Zn 2ϩ being 234.4 kcal/mol, showing stronger electrostatic interaction. The reoptimization for the two most stable modes with the different valent states ͑ϩ1,ϩ2͒ to combine a H 2 O molecule at their each end of Zn ion show that the relative energy ordering does not change, and also resembles their no-H 2 O-combined counterparts. However, an interesting and important observation has been first obtained that single hydration effect can strikingly strengthen the stability of the monovalent OO form though it is still higher by 0.1 kcal/mol in energy than the NO counterpart. Hydration effect of double waters can reverse their relative stability due to the strong hydrogen bond effect in the OO form. Different from the case of the two monovalent hydrated complexes, calculated results for the divalent zinc ion chelated complexes show that with or without single hydration hardly change the value of their relative energy, and hydration strength and glycine deformation difference induced with or without hydration in the two different modes display surprising similarity. So we predict that the further hydration basically do not yield any effect on the relative stability. The prediction for the hydration effect on the glycine-Zn ϩ /Zn 2ϩ system would be also suitable for its analogs, such as glycine-Cu ϩ /Cu 2ϩ and glycine-Ni ϩ /Ni 2ϩ systems, and even suitable for other similar transition metal ion-chelated glycine systems.

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“…Recently, this system was discussed in the literature in connection with the failure of GGA for weak three-electron twocenter bonds. 47 We here propose an alternative remedy, which is based on our observation 16,17 that the present GGA ''exchange'' functionals do not in fact describe ''exact exchange'' very well, but describe the exchange plus nondynamical correlation quite accurately. Since this also appears to hold in the HϩH 2 transition state, that leaves the GGA ''correlation'' functional as the only functional to be corrected for its overestimation of the dynamical correlation in cases of intermediate spin polarization.…”

Section: Comparison Of the Ks And Gga Results For H؉hmentioning

confidence: 99%

Benchmark calculations of chemical reactions in density functional theory: Comparison of the accurate Kohn–Sham solution with generalized gradient approximations for the H2+H and H2+H2 reactions

Schipper

Gritsenko

Baerends

1999

The Journal of Chemical Physics

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101

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The Kohn-Sham ͑KS͒ solution is constructed from an accurate CI density and the KS exchange and correlation energies E x and E c , as well as the corresponding exchange and exchange-correlation energy densities ⑀ x (r) and ⑀ xc (r), which are obtained for the hydrogen abstraction reaction HϩH 2 and the symmetrical four-center exchange reaction H 2 ϩH 2 . The KS quantities are compared with those of the standard GGAs. Comparison shows that the GGA exchange functional represents both exchange and molecular nondynamical left-right correlation, while the GGA correlation functional represents only the dynamical part of the correlation. This role of the GGA exchange functional is especially important for the transition states ͑TS͒ of the reactions where the left-right correlation is enhanced. Standard GGAs tend to underestimate the barrier height for the reaction HϩH 2 and to overestimate it for the reaction H 2 ϩH 2 . For H 2 ϩH 2 the Kohn-Sham orbital degeneracy in the square TS is represented with an equi-ensemble KS solution for both accurate KS/CI and GGA, while near the TS ensemble solutions with unequal occupations of the degenerate highest occupied orbitals are obtained. For the GGA ensemble solution a special ensemble formula for the GGA exchange functional is proposed. Application of this formula to the H 2 ϩH 2 reaction reduces appreciably the reaction barriers calculated with GGAs and leads to much better agreement with the accurate value. The too low GGA barriers for the HϩH 2 reaction are attributed to overestimation of the dynamical correlation in the TS by the GGA correlation functionals. In order to correct this error, it is recommended to modify the dependence of the approximate correlation functionals on the local polarization with the purpose of reducing the approximate correlation energy for intermediate values, which are expected to characterize the TS's of radical abstraction reactions.

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Ground State of the (H₂O)₂⁺ Radical Cation: DFT versus Post-Hartree−Fock Methods

Cited by 238 publications

References 25 publications

Modeling Cu2+-Aβ complexes from computational approaches

Modeling Cu2+-Aβ complexes from computational approaches

Glycine-Zn+/Zn2+ and their hydrates: On the number of water molecules necessary to stabilize the switterionic glycine-Zn+/Zn2+ over the nonzwitterionic ones

Benchmark calculations of chemical reactions in density functional theory: Comparison of the accurate Kohn–Sham solution with generalized gradient approximations for the H2+H and H2+H2 reactions

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