Communication: Density functional theory model for multi-reference systems based on the exact-exchange hole normalization

Laqua, Henryk; Kussmann, Jörg; Ochsenfeld, Christian

doi:10.1063/1.5025334

Cited by 6 publications

(7 citation statements)

References 33 publications

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“…Such molecules usually pose problems for traditional DFT methods, which so far are restricted in the wave function picture to single determinant variants. Fractional occupation numbers can be, however, used and, similar to wave function based methods, multideterminant DFT methods are being developed to solve problems such as double-counting electron correlation. − These are interesting developments, but they have not yet reached the stage of routine methods. Accurate wave function based MO methods still play an important role for checking the reliability of DFT calculations for physical properties, particularly in molecules that are not well described with one Lewis structure.…”

Section: Quantum Chemical Methods For Calculating Molecular Structure...mentioning

confidence: 99%

Chemical Bonding and Bonding Models of Main-Group Compounds

et al. 2019

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The focus of this review is the presentation of the most important aspects of chemical bonding in molecules of the main group atoms according to the current state of knowledge. Special attention is given to the difference between the physical mechanism of covalent bond formation and its description with chemical bonding models, which are often confused. This is partly due to historical reasons, since until the development of quantum theory there was no physical basis for understanding the chemical bond. In the absence of such a basis, chemists developed heuristic models that proved extremely valuable for understanding and predicting experimental studies. The great success of these simple models and the associated rules led to the fact that the model conceptions were regarded as real images of physical reality. The complicated world of quantum theory, which eludes human imagination, made it difficult to link heuristic models of chemical bonding with quantum chemical knowledge. In the early days of quantum chemistry, some suggestions were made which have since proved untenable. In recent decades, there has been a stormy development of quantum chemical methods, which are not limited to the quantitative accuracy of the calculated properties. Also, methods have been developed where the experimentally developed models can be quantitatively expressed and visually represented using mathematically well-defined terms that are derived from quantum chemical calculations. The calculated numbers may however not be measurable values. Nevertheless, as orientation data for the interpretation and classification of experimental findings as well as a guideline for new experiments, they form a coordinate system that defines the multidimensional world of chemistry, which corresponds to the Hilbert space formalism of physics. The nonmeasurability of model values is not a weakness of chemistry but a characteristic by which the infinite complexity of the material world becomes scientifically accessible and very useful for chemical research. This review examines the basis of the commonly used quantum chemical methods for calculating molecules and for analyzing their electronic structure. The bonding situation in selected representative molecules of main-group atoms is discussed. The results are compared with textbook knowledge of common chemistry. CONTENTS1. Introduction 8782 2. The Physical Nature of the Chemical Bond 8783 3. Historical Development and Present Situation of Bonding Models for Main-Group Compounds: The Lewis Paradigm 8786 4. Quantum Chemical Methods for Calculating Molecular Structures and Properties 8787 4.1. Molecular Orbital (MO) Theory 8788 4.2. Density Functional Theory (DFT) 8789 4.3. Valence-Bond (VB) Theory 8790 5. Quantum Chemical Methods for Analyzing the Chemical Bond in Molecules 8790 5.1. Natural Bond Orbital Method (NBO) 8790 5.2. Quantum Theory of Atoms in Molecules (QTAIM) 8791 5.3. Energy Decomposition Analysis and Natural Orbitals for Chemical Valence (EDA-NOCV) 8792 6. Physical Reality and Chemical Bondi...

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Section: Quantum Chemical Methods For Calculating Molecular Structure...mentioning

confidence: 99%

Chemical Bonding and Bonding Models of Main-Group Compounds

et al. 2019

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“…Kohn–Sham density functional theory (KS-DFT) makes use of noninteracting auxiliary orbitals that are described by a single Slater determinant when constructing the one-electron probability density and therefore suffers from this kind of error. Most forms of KS-DFT have been found to perform poorly for systems that have are known to have “multireference” character, and attempts have been made to overcome this limitation. − Thermally-assisted-occupation density functional theory (TAO-DFT) enables the calculation of static correlation within DFT through the use of fractional orbital occupations maintained with a fictitious temperature, θ. ,− The complexity of this method scales similarly to KS-DFT when increasing the number of electrons in the system, and yet it has been shown to give a similar accuracy to computationally more expensive wave function based methods − which scale very rapidly with increasing numbers of electrons. − …”

Section: Introductionmentioning

confidence: 99%

Static Electron Correlation in Anharmonic Molecular Vibrations: A Hybrid TAO-DFT Study

Hanson‐Heine

2022

J. Phys. Chem. A

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Hybrid thermally-assisted-occupation density functional theory is used to examine the effects of static electron correlation on the prediction of a benchmark set of experimentally observed molecular vibrational frequencies. The B3LYP and B97-1 thermally-assisted-occupation measure of static electron correlation is important for describing the vibrations of many of the molecules that make up several popular test sets of experimental data. Shifts are seen for known multireference systems and for many molecules containing atoms from the second row of the periodic table of elements. Several molecules only show significant shifts in select vibrational modes, and significant improvements are seen for the prediction of hydrogen stretching frequencies throughout the test set.

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“…While DFT has improved vastly since its foundation in the 1960s by Hohenberg and Kohn, it is still known to struggle with or fail for highly correlated systems. , Specifically, overall, DFT has shortcomings in treating static correlation that arises in situations with degeneracy or near-degeneracy; this makes it less than ideal for treating species containing f -elements. Though much work has been done and significant progress has been made toward treating multireference systems using DFT, − the efficacy of these methods for f -block elements has not been demonstrated and varies widely depending on the density functional chosen. Rigorous wavefunction-based calculations are therefore important for the understanding of f -block elements, with their low-lying electronic states, many of which are near-degenerate from the highly open-shell nature of most of these elements and from the strong relativistic effects that become significant in heavy elements.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Composite Approaches for Heavy Element Energetics: Ionization Potentials for the Actinide Series of Elements

North

Wilson

2022

J. Phys. Chem. A

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The first, second, and third gas-phase ionization potentials have been determined for the actinide series of elements using an ab initio composite scalar and fully relativistic approach, employing the coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) and Dirac Hartree–Fock (DHF) methods, extrapolated to the complete basis set (CBS) limit. The impact of electron correlation and basis set choice within this framework are examined. Additionally, the first three ionization potentials were obtained using an ab initio heavy element correlation-consistent Composite Approach (here referred to as α-ccCA). This is the first utilization of a ccCA for actinide species.

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Communication: Density functional theory model for multi-reference systems based on the exact-exchange hole normalization

Cited by 6 publications

References 33 publications

Chemical Bonding and Bonding Models of Main-Group Compounds

Chemical Bonding and Bonding Models of Main-Group Compounds

Static Electron Correlation in Anharmonic Molecular Vibrations: A Hybrid TAO-DFT Study

Ab Initio Composite Approaches for Heavy Element Energetics: Ionization Potentials for the Actinide Series of Elements

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