Density‐functional thermochemistry. III. The role of exact exchange

1993 ◽  
Vol 98 (7) ◽  
pp. 5648-5652 ◽  
Author(s):  
Axel D. Becke
Keyword(s):  
Density Functional ◽  
Exact Exchange

Structure of Electronically Reduced N-Donor Bidentate Ligands and Their Heteroleptic Four-Coordinate Zinc Complexes: A Survey of DFT Results

2018 ◽  
Author(s):  
Madanakrishna Katari ◽  
Duncan Carmichael ◽  
Denis Jacquemin ◽  
Gilles Frison
Keyword(s):  
Density Functional ◽  
Structural Changes ◽  
Density Functional Theory Calculations ◽  
Small Degree ◽  
Zinc Complexes ◽  
Hartree Fock ◽  
Exact Exchange ◽  
The Difference ◽  
Geometric Changes

The role of Hartree-Fock exchange in describing the structural changes occurring upon reduction of bipyridine-based ligands and their complexes is investigated in the framework of density functional theory calculations. A set of 4 free ligands in their neutral and radical anionic forms, and 2 of their zinc complexes in their dicationic and monocationic radical forms, is used to compare a large panel of pure, conventional, and long-range corrected hybrid DFT functionals; coupled cluster single and double calculations are used alongside experimental results as benchmarks. Particular attention has been devoted to the magnitude of the change, upon reduction, of the D-parameter, which measures the difference between the Cpy-Cpy and the C-N bond lengths in bipyridine ligand and is known to experimentally correlate with the charge of the ligands. Our results indicate that the structural changes significantly depend on the amount of exact exchange included in the functional. A progressive evolution is observed for the free ligands, whereas two distinct sets of results are obtained for the complexes. Functionals with a small degree of HF exchange, e.g., B3LYP, do not adequately describe geometric changes for the considered species and, quite surprisingly, the same holds for the CC2 method. The best agreement to experimental and CCSD values is obtained with functionals including a significant but not excessive part of exact exchange, e.g., CAM-B3LYP, M06-2X, and wB97X-D. The location of the added electron upon reduction, which depends on the self-interaction error, is used to rationalize these outcomes.<br>

Antiferromagnetic vs. non-magnetic ε phase of solid oxygen. Periodic density functional theory studies using a localized atomic basis set and the role of exact exchange

2017 ◽  
Vol 19 (4) ◽  
pp. 2826-2833 ◽  
Author(s):  
A. Ramírez-Solís ◽  
C. M. Zicovich-Wilson ◽  
R. Hernández-Lamoneda ◽  
A. J. Ochoa-Calle
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Basis Set ◽  
Functional Theory ◽  
Solid Oxygen ◽  
Ε Phase ◽  
Exact Exchange

The question of the non-magnetic (NM) vs. antiferromagnetic (AF) nature of the ε phase of solid oxygen is a matter of great interest and continuing debate.

Density-functional theory (hyper)polarizabilities of push-pull π-conjugated systems: Treatment of exact exchange and role of correlation

2005 ◽  
Vol 123 (1) ◽  
pp. 014319 ◽  
Author(s):  
Felipe A. Bulat ◽  
Alejandro Toro-Labbé ◽  
Benoît Champagne ◽  
Bernard Kirtman ◽  
Weitao Yang
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Functional Theory ◽  
Conjugated Systems ◽  
Exact Exchange

Structure of Electronically Reduced N-Donor Bidentate Ligands and Their Heteroleptic Four-Coordinate Zinc Complexes: A Survey of DFT Results

2018 ◽  
Author(s):  
Madanakrishna Katari ◽  
Duncan Carmichael ◽  
Denis Jacquemin ◽  
Gilles Frison
Keyword(s):  
Density Functional ◽  
Structural Changes ◽  
Density Functional Theory Calculations ◽  
Small Degree ◽  
Zinc Complexes ◽  
Hartree Fock ◽  
Exact Exchange ◽  
The Difference ◽  
Geometric Changes

The role of Hartree-Fock exchange in describing the structural changes occurring upon reduction of bipyridine-based ligands and their complexes is investigated in the framework of density functional theory calculations. A set of 4 free ligands in their neutral and radical anionic forms, and 2 of their zinc complexes in their dicationic and monocationic radical forms, is used to compare a large panel of pure, conventional, and long-range corrected hybrid DFT functionals; coupled cluster single and double calculations are used alongside experimental results as benchmarks. Particular attention has been devoted to the magnitude of the change, upon reduction, of the D-parameter, which measures the difference between the Cpy-Cpy and the C-N bond lengths in bipyridine ligand and is known to experimentally correlate with the charge of the ligands. Our results indicate that the structural changes significantly depend on the amount of exact exchange included in the functional. A progressive evolution is observed for the free ligands, whereas two distinct sets of results are obtained for the complexes. Functionals with a small degree of HF exchange, e.g., B3LYP, do not adequately describe geometric changes for the considered species and, quite surprisingly, the same holds for the CC2 method. The best agreement to experimental and CCSD values is obtained with functionals including a significant but not excessive part of exact exchange, e.g., CAM-B3LYP, M06-2X, and wB97X-D. The location of the added electron upon reduction, which depends on the self-interaction error, is used to rationalize these outcomes.<br>

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

2020 ◽  
Author(s):  
Tulin Okbinoglu ◽  
Pierre Kennepohl
Keyword(s):  
Density Functional ◽  
Chemical Properties ◽  
Functional Theory ◽  
Rotational Barriers ◽  
Td Dft ◽  
Nitrogen Bonds ◽  
X Ray Absorption ◽  
Related Compounds ◽  
And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

Sign in / Sign up

Export Citation Format

Share Document