Numerical computation of critical properties and atomic basins from three-dimensional grid electron densities

Claudine Katan ‘s present address : CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceInteGriTy is a software package that performs topological analysis following the AIM (atoms in molecules) approach on electron densities given on three-dimensional grids. Tricubic interpolation is used to obtain the density, its gradient and the Hessian matrix at any required position. Critical points and integrated atomic properties have been derived from theoretical densities calculated for the compounds NaCl and TTF-(2,5)Cl(2)BQ (tetrathiafulvalene-2,5-dichlorobenzoquinone), thus covering the different kinds of chemical bonds: ionic, covalent, hydrogen bonds and other intermolecular contacts

Intramolecular Electronic Redistribution Coupled to Hydrogen Bonding: An Important Mechanism for the "Neutral-to-Ionic" Transition

International audienceThe part played by the electronic interactions in the uncommon "neutral-to-ionic" (N-I) structural transition occurring in some mixed stack organic compounds, such as tetrathiafulvalene-chloranil (TTF-CA), is analyzed by ab initio electronic structure calculations. It is shown that the charge-transfer variation occurring in the valence band along the mixed stacks of donor and acceptor molecules is coupled via an intramolecular mechanism to a deformation of the electronic cloud in lower bands. The lower bands affected by this redistribution are also those which are implicated in the interstack hydrogen bonds, and a charge-transfer increase produces a strengthening of these hydrogen bonds. This important mechanism, which associates the charge-transfer variation to the anisotropic lattice contractions in the crystal, has never been considered up to now

Designing a new two-dimensional molecular layout by hydrogen bonding

Claudine Katan ‘s present address : CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceDesigning a New Two-Dimensional Molecular Layout by Hydrogen Bondin

Theoretical Investigation of the Ground-State Properties of DMTTF−CA: A Step toward the Understanding of Charge Transfer Complexes Undergoing the Neutral-to-Ionic Phase Transition

International audienceA detailed theoretical study based on first-principles DFT calculations is reported for the charge transfer complex 2,6-dimethyltetrathiafulvalene-p-chloranil (DMTTF−CA). Charge transfer estimates reveal that no periodic ordering of neutral and ionic layers is obtained in the low-temperature phase of DMTTF−CA. Similarities and differences with other mixed-stack charge transfer complexes are discussed with the help of a topological analysis of the electron density. Our results also show that the most popular model in this field, which is based on the balance between the cost of ionization and the gain in Madelung energy, should be used with great care. These molecules are far from being point charges, and molecular deformation and polarization should not be ignored

Conformational change of tetrahydroxyquinone molecules deposited on Ag(111)

International audienc

Influence of stress on hydrogen-bond formation in a halogenated phthalocyanine network

International audienc

Inhomogeneous relaxation of a molecular layer on an insulator due to compressive stress

We discuss the inhomogeneous stress relaxation of a monolayer of hexahydroxytriphenylene (HHTP) which adopts the rare line-on-line (lol) coincidence on KCl(001) and forms Moiré patterns. The fact that the hexagonal HHTP layer is uniaxially compressed along the lol makes this system an ideal candidate to discuss the influence of inhomogeneous stress relaxation. Our work is a combination of noncontact atomic force microscopy experiments, of density functional theory and potential energy calculations, and of a thorough interpretation by means of the Frenkel-Kontorova model. We show that the assumption of a homogeneous molecular layer is not valid for this organic-inorganic heteroepitaxial system since the best calculated energy configuration correlates with the experimental data only if inhomogeneous relaxations of the layer are taken into account

Experimental and ab initio study of the O3_3 detection at the CuO (111) surface

International audienceCombining experiments and first-principles calculations, we present in this paper a detailed study of the O$_3$ detection mechanism on the CuO (111) surface. The exchange-correlation functional is treated within both the LDA and the GGA including the spin polarization. In order to better take into account the on-site electronic interactions between $3d$ electrons of Cu atoms a Hubbard term U has to be added in all calculations. We show that the O$_3$ molecule is reduced to a O$_2$ molecule with an enthalpy of reaction of −1.11 eV (−1.15 eV) within LDA+U (GGA+U). Along the reaction path, the O$_3$ molecules are first physisorbed with a large adsorption energy of −1.83 eV (−1.03 eV) and a significant charge transfer from the surface to the molecule. The p-doping strengthening is compared to the electrical response of a CuO based sensor under O$_3$ exposure

Ab initio study of oxygen point defects on tungsten trioxide surface

International audienceThe gas response of tungsten trioxide (WO 3) based sensors strongly depends on the surface properties. Reconstructed surfaces and oxygen point defects at the surface of the monoclinic WO 3 are studied using a self-consistent scheme based on first-principle. The oxygen vacancy is found to be the predominant defect independently of the oxygen partial pressure. Indeed, under rich oxygen atmosphere the formation enthalpies are found to be 1.45 eV in LDA (1.28 eV in GGA) for the oxygen vacancy instead of 2.70 eV (2.42 eV) for the oxygen adatom. When the oxygen partial pressure is lowered, the oxygen vacancy formation enthalpy decreases and becomes exothermic under very O-poor condition (-1.65 eV in LDA and-1.36 eV in GGA). On the other hand, the formation enthalpy of an oxygen adatom rises. Finally, the oxygen vacancy formation acts as a n–doping by introducing negative charge carriers at the bottom of the conduction band. All these results can be very helpful in order to explain the electrical resistivity measurements