Accurate static electric dipole polarizability calculation of +3 charged lanthanide ions

An accurate determination of the heavy element static atomic dipole polarizability is a challenge for theoretical methods. We present in this paper computed values of the dipole polarizability of the lanthanide ions from La3+ to Lu3+. The results were obtained by performing fully relativistic and pseudopotential calculations including the treatment of open-shell systems. We have shown that, in order to obtain accurate results, it is essential to take into account scalar relativistic effects, core polarization and flexibility of the basis sets. Finally, we present a database of reference values of dipole polarizability for the Ln3+ ions

Vibrational mode assignment of finite temperature infrared spectra using the AMOEBA polarizable force field †

International audienceThe calculation of infrared spectra by molecular dynamics simulations based on the AMOEBA polarizable force field has recently been demonstrated [Semrouni et al., J. Chem. Theory Comput., 2014, 10, 3190]. While this approach allows access to temperature and anharmonicity effects, band assignment requires additional tools, which we describe in this paper. The Driven Molecular Dynamics approach, originally developed by Bowman, Kaledin et al. [Bowman et al. J. Chem. Phys., 2003, 119, 646, Kaledin et al. J. Chem. Phys., 2004, 121, 5646] has been adapted and associated with AMOEBA. Its advantages and limitations are described. The IR spectrum of the Ac-Phe-Ala-NH 2 model peptide is analyzed in detail. In addition to differentiation of conformations by reproducing frequency shifts due to non-covalent interactions, DMD allows visualizing the temperature-dependent vibrational modes

Theoretical study of the hydrated Gd3+ ion: Structure, dynamics, and charge transfer

The dynamical processes taking place in the first coordination shells of the gadolinium (III) ion are important for improving the contrast agent efficiency in magnetic-resonance imaging. An extensive study of the gadolinium (III) ion solvated by a water cluster is reported, based on molecular dynamics simulations. The AMOEBA force field [P. Y. Ren and J. W. Ponder, J. Phys. Chem. B 107, 5933 (2003)] that includes many-body polarization effects is used to describe the interactions among water molecules, and is extended here to treat the interactions between them and the gadolinium ion. In this purpose accurate ab initio calculations have been performed on Gd3+-H2O for extracting the relevant parameters. Structural data of the first two coordination shells and some dynamical properties such as the water exchange rate between the first and second coordination shells are compared to available experimental results. We also investigate the charge transfer processes between the ion and its solvent, using a fluctuating charges model fitted to reproduce electronic structure calculations on [Gd(H2O)n]3+ complexes, with n ranging from 1 to 8. Charge transfer is seen to be significant (about one electron) and correlated with the instantaneous coordination of the ion

Electronic structure theory to decipher the chemical bonding in actinide systems

International audienceThe chemical bonding in actinide compounds is usually analysed by inspecting the shape and the occupation of the orbitals or by calculating bond orders which are based on orbital overlap and occupation numbers. However, this may not give a definite answer because the choice of the partitioning method may strongly influence the result possibly leading to qualitatively different answers. In this review, we summarized the state-of-the-art of methods dedicated to the theoretical characterisation of bonding including charge, orbital, quantum chemical topology and energy decomposition analyses. This review is not exhaustive but aims to highlight some of the ways opened up by recent methodological developments. Various examples have been chosen to illustrate this progress

The 32-electron principle: A new magic number

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Theoretical insights into the chemical bonding in actinide complexes

International audienceAbstract The chemical bonding in actinide compounds is usually analyzed by inspecting the shape and the occupation of the orbitals or by calculating bond orders which are based on orbital overlap and occupation numbers. However, this may not give a definite answer because the choice of the partitioning method may strongly influence the result leading sometimes to qualitatively different answers. This review highlights that the joint and complementary tools such as charge, orbital, quantum chemical topology and energy decomposition analyses are very powerful to understand chemical bonding in the field of actinide chemistry. However, understanding the actinide–ligand bond is not straightforward and requires caution in the use of these methods. This review is illustrated through applications to newly discovered bent actinocene compounds and actinide endohedral clusters fulfilling a 32-electron rule

Theoretical study of the bent U(η8-C8H8)2(CN)- complex

International audienceThe ground-state electronic structure of the cyanido complex [U(η8-C8H8)2(CN)]− as well as the thermodynamic properties and infrared spectrum are investigated using density functional theory including scalar relativistic effects. The complex is compared with the well-known uranocene U(η8-C8H8)2. Despite the broken symmetry, the gain in electrostatic interaction and a significant uranium-CN− orbital interaction is sufficient to stabilize the bent CN− complex with respect to uranocene. The formation of the CN− complex is exothermic justifying the recently experimentally reported compound.. © 2011 Springer-Verlag