Theoretical studies on the electronic properties and the chemical bonding of transition metal complexes using dft and ligand field theory

The research activity within our laboratory of computational chemistry at the University of Fribourg is presented. In this review, a brief outline of a recently proposed Ligand Field Density Functional Theory (LFDFT) model for single nuclear and its extension to dimer transition metal complexes is given. Applications of the model to dinuclear complexes are illustrated for the interpretation of exchange coupling in the bis-μ- hydroxo-bridged dimer of Cu(II) and to the description of the quadruple metal-metal bond in Re₂Cl₈²⁻. The analysis of the chemical bonding is compared with results obtained using other approaches, i.e. the Extended Transition State model and the Electron Localization Function. It is shown that the DFT supported Ligand Field Theory provides consistent description of the ground and excited state properties of transition metal complexes

Multiplets of free d- and f-metal ions: A systematic DFT study

In this work we apply in a systematic way our multi-determinantal model to calculate the fine structure of the whole atomic multiplet manifold. The key feature of this approach is the explicit treatment of near-degeneracy correlation using ad hoc configuration interaction (CI) within the active space of Kohn–Sham (KS) orbitals with open d- or f-shells. The calculation of the CI-matrices is based on a central symmetry decomposition of the energies of all single determinants (micro-states) calculated according to Density Functional Theory (DFT) for frozen KS-orbitals corresponding to the averaged configuration, eventually with fractional occupations, of the d- or f-orbitals and/or the direct calculation of the electrostatic reduced matrix elements (Racah or Slater–Condon parameters) occurring in the corresponding active space. We performed DFT calculations on all divalent and trivalent d²–d⁸ metal ions, as well as the f²–f¹² lanthanide(III) ions. We compare the results of both variants of the method with the data available in the literature. Both procedures yield multiplet energies with an accuracy of about hundred wave numbers and fine structure splitting accurate to less than a tenth of this amount

Improved coupled perturbed Hartree–Fock and Kohn–Sham convergence acceleration

A derivative version of the well-known direct inversion in the iterative subspace (DIIS) algorithm is presented. The method is used to solve the coupled perturbed Hartree–Fock (CPHF) equation to obtain the first and second derivatives of the density matrix with respect to an external electric field which, in this case, leads to the electric molecular polarizability and hyperpolarizability. Some comparisons are presented and the method shows good convergences in almost all cases

Reference 360: A Holistic Approach to Reference Instruction

Knowledge of the Reference and User Services Association (RUSA) Guidelines for Behavioral Performance of the Reference and Information Service Providers and an awareness of the books, databases, and other resources generally available in library reference collections are excellent pathways to train confident practitioners in reference service. Procedural knowledge of RUSA guidelines and intellectual ability are the basic skills required to answer a reference question. Yet at times, the reference interview is a labyrinthine process laden with confusion and emotion. Tacit knowledge – unwritten, unspoken knowledge based on experience, insights, and intuition – is a skill that allows librarians to navigate the reference transaction labyrinth and leave the patron feeling validated and confident in their research experience. Library patrons today are typically not looking for a finite piece of information, but rather are trying to sift through and interpret the massive amount of unmediated information available to them. This means patrons are operating under a high cognitive load before they begin their library research, often leaving them anxious and unmoored before they venture to the reference desk for advice. Because of this, it is essential that library students view the reference transaction holistically, as they interact with the patron. In order to create an environment conducive to the holistic reference transaction, empathy, communication, and critical thinking should be at the forefront of a new librarian’s skillset. Emotional intelligence should be studied and practiced to ensure library students leave a reference course with the ability to not only meet their patrons’ information needs, but also to help their patrons feel comfortable navigating the library and its resources. The practice of mindfulness ensures self-awareness and openness to new information and promotes calm, clear interactions with patrons. Finally, critical reflection upon one’s reference training and practice while in the classroom and beyond is key to incorporating the ideals of emotional intelligence and mindfulness into a comprehensive reference librarian’s skillset

Reference 360: A Holistic Approach to Reference Instruction

Reference 360: A Holistic Approach to Reference Instruction is a chapter in the book Teaching Reference Today : New Directions, Novel Approaches. The book is edited by L. A. Ellis, Editor, (pp.98-117), Rowman & Littlefield, 2016. Publisher\u27s description: Reference and Information Services, if it may still be referred to by this term, is an evolving outreach service in libraries. This is not only due to Google and the Internet, but also other technological advances afford users online access to a plethora of content, free and proprietary. This evolution has also caused a shift in the theories and practices (especially, core functions and values) of reference and information services as library schools seek greater alignment with practitioners and libraries on the forefront of these changes.As academics and practitioners work together to educate library students on the kinds of changes happening in reference and information services, they are rethinking their curriculum and assignments to incorporate real-world challenges adaptive to user needs. Likewise, libraries may work through their regional library consortia to plan professional development workshops or training sessions to teach new skills and methods of approach required for such changing services.Here’s a tool for library school instructors, library students, professional development instructors, and current librarians poised to change, which specifically addresses the pedagogy of reference and information services in flux.https://openriver.winona.edu/libraryfacultyworks/1001/thumbnail.jp

Chemical Bonding in Molecules and Complexes Containing d-Elements Based on DFT

Summary.: Metal-ligand bonding in transition metal halide molecules and complexes with different central ions, oxidations states, and coordination numbers: CrIIIX63−, CrIVX4, CrIIX2 (X = F,Cl,Br,I), MIIICl63−(M = Mo,W), MIII(H2O)63+(M = Cr,Co) and Re2Cl82− has been studied in terms of the Extended Transition State (ETS) energy patitioning scheme within the DFT and electron density analysis (the Laplacian of the electron density and the electronic localization function). Bonding is found to be dominated by ionicity in all cases, especially so for complexes with higher coordination numbers. Covalent contributions to the metal-ligand bond are found to be mainly due to the nd-electrons and to lesser extent due to the metal (n + 1)s and (n + 1)p-orbitals, contributions from (n+1)s increasing when going to lower coordination numbers. Metal-ligand bonding analysis have been used in order to check some concepts emerging from ligand field theory when applied to the spectroscopy and magnetism of transition metal complexes. It is pointed out that for complexes of high symmetry (MX6, Oh, MX4, Td, and MX2, D∞h) electron density analyses gain interpretative power when partitioned into contributions from occupied orbitals of different symmetr

Frustrated Hubbard ladders and superconductivity in κ\kappa-BEDT-TTF organic compounds

Half-filled two-leg Hubbard ladders have spin-gapped short-range antiferromagnetic correlations while three-leg ladders have power law antoferromagnetic correlations, and both systems have d_{x^2-y^2}-power law pairing correlations when they are doped. Thus these ladders exhibit some of the phenomenology seen in the layered cuprates. Here we report results for half-filled frustrated Hubbard ladders, based upon ladder segments taken from a tight-binding model of kappa-BEDT-TTF. Although these ladders are half-filled, varying the degree of frustration can drive them across an insulator-metal transition. We suggest that the spin, charge and pairing correlations of these frustrated ladders near the insulator-metal transition provide support for the notion that kappa-BEDT-TTF is a strongly correlated superconductor

Optical properties of germanium dioxide in the rutile structure

We present first-principles calculations for the optical properties of germanium dioxide in the rutile structure. The electronic band structure has been calculated self-consistently within the local density approximation using the full-potential linearized augmented plane wave method. The electronic band structure shows that the fundamental energy gap is direct at the center of the Brillouin zone. The determinant role of a band structure computation with respect to the analysis of the optical properties is discussed