Structure and EPR parameters of CuC2H2 from a density functional approach

Barone, Vincenzo; Fournier, René; Mele, Franca; Russo, Nino; Adamo, Carlo

doi:10.1016/0009-2614(95)00323-v

Cited by 20 publications

(22 citation statements)

References 32 publications

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“…As in the case of the CuO 2 complex, two energy minima are, in principle, possible for CuC 2 H 2 (see Figure 3). In this case EPR experiments 30,31 seem to be compatible only with the C 2V side-on structure, whereas previous DF studies, 46 carried out with a standard GGA model, suggest that an end-on C s structure is more stable. The results obtained in the present study for the two different structures of CuC 2 H 2 are summarized in Tables 5 and 6.…”

Section: Resultscontrasting

confidence: 65%

“…In this first study we have selected a transition metal, i.e. copper, without nearly degenerate electronic states and for which several experimental − and conventional quantum-mechanical − studies are available. Furthermore, the binding energies ( D e ) of the studied complexes cover a wide range, going from strong covalent bonds ( D e > 50 kcal/mol) to weak noncovalent interactions ( D e < 15 kcal/mol).…”

Section: Introductionmentioning

confidence: 99%

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Validation of Hybrid Density Functional/Hartree−Fock Approaches for the Study of Homogeneous Catalysis

Barone

Adamo

1996

J. Phys. Chem.

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The potentialities of a hybrid density functional/Hartree-Fock approach in the study of homogeneous catalysis have been investigated by a comprehensive study of binary adducts of copper atom characterized by strong (Cu 2 , CuH, CuCH 3 ) or weak (CuCO, CuNO, CuO 2 , CuC 2 H 2 ) metal-ligand interactions. The results confirm that this approach describes with good accuracy several properties of transition metal complexes, giving in particular binding energies close to the best available post-Hartree-Fock and experimental results. Besides the reasonable computation times, the possibility of avoiding high angular momentum basis functions, and the negligible basis set superposition error, the strength of hybrid approaches is their remarkably constant accuracy for closed-and open-shell systems and for strong covalent or weak donor-acceptor interactions. Furthermore, the ease of interpretation of single-determinant methods is retained. This allows the use of powerful energy decomposition tools for gaining further insight into the origin of different bonding patterns.

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Section: Resultscontrasting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Validation of Hybrid Density Functional/Hartree−Fock Approaches for the Study of Homogeneous Catalysis

Barone

Adamo

1996

J. Phys. Chem.

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“…DFT Calculations . Density functional theory, in its modern LCAO form, has only recently been employed in hfcc calculations of small radical systems. ,− ,,, Barone has investigated the performance of the functionals employed in the present study, using a larger, partly modified, TZP basis set. 56a,f He concluded that B3-LYP generally provides the most accurate hfcc's, and that these are comparable in accuracy to high-level CI-based methods (MRCI, QCISD). In previous work, it has also been shown that the gradient corrections according to Perdew and Wang for the exchange (PW) 58 and by Perdew for the correlation (P86), together with the IGLO-III basis set, provide a very effective combination for calculating radical properties to reasonable accuracy.…”

Section: Resultsmentioning

confidence: 99%

“…The best overall accuracy of the DFT approaches tested here is found for B3-LYP using either of these two basis sets, for which the results are better than QCID but not nearly as good as QCISD, as reflected in the tabulated mean absolute deviations. Some improvement might be achieved with even larger basis sets 56a. Due to the cost effectiveness of the DFT-based methods, increasing the basis set sizes is still possible without the calculations becoming intractable from a computational point of view.…”

Section: Resultsmentioning

confidence: 99%

Assessment of Procedures for Calculating Radical Hyperfine Structures

1997

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The effects of different basis sets and computational methods on calculated isotropic hyperfine couplings have been investigated for a set of representative small radicals (OH, H2O+, CN, HCN-, FCN-, HCCH-, CH3, CH4 +, NH2, NO2, and H2CO+). Particular emphasis has been placed on the performance of the QCISD approach, when used in combination with moderately large basis sets. It is found that the 6-311+G(2df,p) basis set generally gives good results and that the IGLO-III basis set performs nearly as well. The cc-pVXZ and aug-cc-pVXZ basis sets, on the other hand, display large and unpredictable fluctuations in hyperfine couplings even at the cc-pVQZ level. As noted previously, the reason for this erroneous behavior can be traced to the contraction of the s-shell. The error due to the unbalanced nature of the pVXZ basis sets is greatly reduced on going to the core-valence correlated aug-cc-pCVXZ sets. The calculated hyperfine coupling constants are very sensitive to changes in geometry. In turn, the geometries of radical anion systems in particular are sensitive to level of theory. The 6-311+G(2df,p) basis set has also been tested with other spin-unrestricted methods (UHF, UMP2, UQCID, and five DFT functionals), but none of these are found to perform comparably to QCISD. Inclusion of triple excitations (QCISD(T)) leads to hyperfine couplings that generally lie within 2−3 G of the QCISD results.

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“…Thus, the situation resembles more that known for main-group π-type radicals, with the (slight) difference that we have a very polarizable M-shell below the 4p ztype SOMO. The description for [Cu(CO) 3 ] is thus considerably more difficult than for Cu(C 2 H 2 ) or Cu(CO) studied previously with DFT methods by Barone et al,14,15 where large positive direct contributions from a metal 4s-type SOMO dominate.…”

Section: H] and [Co(co) 4 ]mentioning

confidence: 98%

A Critical Validation of Density Functional and Coupled-Cluster Approaches for the Calculation of EPR Hyperfine Coupling Constants in Transition Metal Complexes

1999

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The performance of various density functional approaches for the calculation of electron paramagnetic resonance (EPR) hyperfine coupling constants in transition metal complexes has been evaluated critically by comparison with experimental data and high-level coupled-cluster results for 21 systems, representing a large variety of different electronic situations. While both gradient-corrected and hybrid functionals allow the calculation of isotropic metal hyperfine coupling constants to within ca. 10-15% for the less critical cases (e.g., ScO, TiN, TiO, VO, MnO, MnF), none of the functionals investigated performs well for all complexes. Gradient-corrected functionals tend to underestimate the important core-shell spin polarization. While this may be improved by exact-exchange mixing in some cases, the accompanying spin contamination may even lead to a deterioration of the results for other complexes. We also identify cases, where essentially none of the functionals performs satisfactorily. In the absence of a "universal functional", the functionals to be applied to the calculation of hyperfine couplings in certain areas of transition metal chemistry have to be carefully selected. Desirable, improved functionals should provide sufficiently large spin polarization for core and valence shells without exaggerating it for the latter (and thus introducing spin contamination). Coupling anisotropies and coupling constants for ligand nuclei are also discussed. The computationally much more demanding coupled cluster (CCSD and CCSD(T)) methods, which have been applied to a subset of complexes, show good performance, even when a UHF reference wave function is moderately spin-contaminated.

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Structure and EPR parameters of CuC2H2 from a density functional approach

Cited by 20 publications

References 32 publications

Validation of Hybrid Density Functional/Hartree−Fock Approaches for the Study of Homogeneous Catalysis

Validation of Hybrid Density Functional/Hartree−Fock Approaches for the Study of Homogeneous Catalysis

Assessment of Procedures for Calculating Radical Hyperfine Structures

A Critical Validation of Density Functional and Coupled-Cluster Approaches for the Calculation of EPR Hyperfine Coupling Constants in Transition Metal Complexes

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