various coordination environments. In this spirit, the following chapters are not
strictly ordered either according to the level of theory or along formal distinction
with respect to the branch of chemistry or physics, but cover rather related fields,
combining various levels of theory and experiment.
The initial batch of five chapters deals with magnetic interactions, untypical
systems, and related dedicated theoretical approaches. Chapter “The Electronic
Determinants of Spin Crossover Described by Density Functional Theory” by
Kasper P. Kepp deals with spin crossover (SCO) phenomenon which plays a vital
role in living systems and in many emerging technologies. In line with the introductory paragraphs, the accurate prediction and design of SCO systems are of high
current priority, while SCO tendency is extremely sensitive not only to the level
of theory but also to its ability to cover such physical effects as dispersion, relativistic effects, and vibrational entropy for large molecular systems. It is shown that
the density functional theory (DFT) is the tool of choice that can be predictive for
this purpose only if the study is carried out scrupulously. A similar approach is
taken in Chapter “Anisotropic Magnetic Spin Interactions of Transition Metal
Complexes and Metalloenzymes from Spectroscopy and Quantum Chemistry”
where Matthias Stein on example of transition metal-containing model complexes
and metalloenzymes discusses the advancement of DFT computational approaches
to calculate the parameters of the effective Spin Hamiltonian such as the electronic
g- and hyperfine tensors in order to support the analysis and interpretation of
complex magnetic resonance spectra. Chapter “Non-covalent Interactions in
Selected Transition Metal Complexes” by Filip Sagan and Mariusz P. Mitoraj
discusses how DFT is able to describe non-covalent chemical interactions in
transition metal complexes where routine DFT methods have been known to
occasionally fail. The authors illustrate on several examples of nonstandard bonds
that good separation of donation (ligand to metal) and back-donation (metal to
ligand) charge transfer processes, which govern this type of bonding, may be done
by proper analysis of the deformation density.
Different approach is taken by Vera Krewald and Dimitrios A. Pantazis (Chapter
“Applications of the Density Matrix Renormalization Group to Exchange-Coupled
Transition Metal Systems”). This chapter deals with inherently multireference
problem, like oligonuclear transition metal complexes containing magnetically
coupled open-shell ions, not always tractable by broken-symmetry DFT. In such
cases, the use of multireference methods remains the deal to treat the exchange
coupling. However, the applicability of these methods has been severely restricted
due to their computational cost, and only in recent years, the introduction of the
density matrix renormalization group (DMRG) to quantum chemistry has enabled
the multireference treatment of exchange-coupled transition metal systems. The first
detailed applications of DMRG-based methods to exchange-coupled systems are
reviewed, and the lessons learned so far regarding the applicability, apparent limitations, and future promise of this approach are discussed. In the same spirit,
Chapter “New Strategies in Modeling Electronic Structures and Properties with
Applications to Actinides” is written by Aleksandra Leszczyk, Paweł Tecmer, and
Katharina Boguslawski. After a short overview of relativistic Hamiltonians,
vi
Preface
strictly ordered either according to the level of theory or along formal distinction
with respect to the branch of chemistry or physics, but cover rather related fields,
combining various levels of theory and experiment.
The initial batch of five chapters deals with magnetic interactions, untypical
systems, and related dedicated theoretical approaches. Chapter “The Electronic
Determinants of Spin Crossover Described by Density Functional Theory” by
Kasper P. Kepp deals with spin crossover (SCO) phenomenon which plays a vital
role in living systems and in many emerging technologies. In line with the introductory paragraphs, the accurate prediction and design of SCO systems are of high
current priority, while SCO tendency is extremely sensitive not only to the level
of theory but also to its ability to cover such physical effects as dispersion, relativistic effects, and vibrational entropy for large molecular systems. It is shown that
the density functional theory (DFT) is the tool of choice that can be predictive for
this purpose only if the study is carried out scrupulously. A similar approach is
taken in Chapter “Anisotropic Magnetic Spin Interactions of Transition Metal
Complexes and Metalloenzymes from Spectroscopy and Quantum Chemistry”
where Matthias Stein on example of transition metal-containing model complexes
and metalloenzymes discusses the advancement of DFT computational approaches
to calculate the parameters of the effective Spin Hamiltonian such as the electronic
g- and hyperfine tensors in order to support the analysis and interpretation of
complex magnetic resonance spectra. Chapter “Non-covalent Interactions in
Selected Transition Metal Complexes” by Filip Sagan and Mariusz P. Mitoraj
discusses how DFT is able to describe non-covalent chemical interactions in
transition metal complexes where routine DFT methods have been known to
occasionally fail. The authors illustrate on several examples of nonstandard bonds
that good separation of donation (ligand to metal) and back-donation (metal to
ligand) charge transfer processes, which govern this type of bonding, may be done
by proper analysis of the deformation density.
Different approach is taken by Vera Krewald and Dimitrios A. Pantazis (Chapter
“Applications of the Density Matrix Renormalization Group to Exchange-Coupled
Transition Metal Systems”). This chapter deals with inherently multireference
problem, like oligonuclear transition metal complexes containing magnetically
coupled open-shell ions, not always tractable by broken-symmetry DFT. In such
cases, the use of multireference methods remains the deal to treat the exchange
coupling. However, the applicability of these methods has been severely restricted
due to their computational cost, and only in recent years, the introduction of the
density matrix renormalization group (DMRG) to quantum chemistry has enabled
the multireference treatment of exchange-coupled transition metal systems. The first
detailed applications of DMRG-based methods to exchange-coupled systems are
reviewed, and the lessons learned so far regarding the applicability, apparent limitations, and future promise of this approach are discussed. In the same spirit,
Chapter “New Strategies in Modeling Electronic Structures and Properties with
Applications to Actinides” is written by Aleksandra Leszczyk, Paweł Tecmer, and
Katharina Boguslawski. After a short overview of relativistic Hamiltonians,
vi
Preface