Search results for "Van der Waals radius"
showing 10 items of 24 documents
Dipole Moment Surface of the van der Waals Complex CH4–N2
2010
The interaction-induced dipole moment surface of the van der Waals CH(4)-N(2) complex has been calculated for a broad range of intermolecular separations R and configurations in the approximation of the rigid interacting molecules at the MP2 and CCSD(T) levels of theory using the correlation-consistent aug-cc-pVTZ basis set with the basis set superposition error correction. The simple model to account for the exchange effects in the range of small overlap of the electron shells of interacting molecules and the induction and dispersion interactions for large R has been suggested. This model allows describing the dipole moment of van der Waals complexes in analytical form both for large R, wh…
Size Dependence of Tracer Diffusion in Supercooled Liquids
1996
We have determined by forced Rayleigh scattering the diffusion coefficients D of several photochromic tracers with van der Waals radii between 0.38 and 8 nm (the largest ones being photolabeled polystyrene micronetworks) in 10 glass-forming liquids at temperatures between the glass temperature Tg and ∼1.2Tg. The results were analyzed in terms of power law plots, D(T) ∝ T/η(T)ξ, where η is the solvent shear viscosity, and temperature shifts, D(T) ∝ T/η(T + ΔT). The shift ΔT was related with the width of the rotational correlation time distribution via the time−temperature superposition principle.
New dimension indices for the characterization of the solvent-accessible surface
2001
van der Waals interactions between excited atoms in generic environments
2015
We consider the the van der Waals force involving excited atoms in general environments, constituted by magnetodielectric bodies. We develop a dynamical approach studying the dynamics of the atoms and the field, mutually coupled. When only one atom is excited, our dynamical theory suggests that for large distances the van der Waals force acting on the ground-state atom is monotonic, while the force acting in the excited atom is spatially oscillating. We show how this latter force can be related to the known oscillating Casimir--Polder force on an excited atom near a (ground-state) body. Our force also reveals a population-induced dynamics: for times much larger that the atomic lifetime the …
Metallophilic interactions in polymeric group 11 thiols
2016
Three polymeric group 11 transition metal polymers featuring metallophilic interactions were obtained directly via self-assembly of metal ions and 4-pyridinethiol ligands. In the cationic [Cu2(S-pyH)4]n2+ with [ZnCl4]n2− counterion (1) and in the neutral [Ag(S-py) (S-pyH)]n (2) 4-pyridinethiol (S-pyH) and its deprotonated form (S-py) are coordinated through the sulfur atom. Both ligands are acting as bridging ligands linking the metal centers together. In the solid state, the gold(I) polymer [Au(S-pyH)2]Cl (3) consists of the repeating cationic [Au(S-pyH)2]+ units held together by aurophilic interactions. Compound 1 is a zig-zag chain, whereas the metal chains in the structures of 2 and 3 a…
Very close I⋯As and I⋯Sb interactions in trimethylpnictogen-pentafluoroiodobenzene cocrystals
2022
The cocrystals (CH3)3As·C6F5I (1) and (CH3)3Sb·C6F5I (2) were generated in situ from equimolar mixtures of their components. 1 and 2 show very close I⋯As and I⋯Sb directional intermolecular interactions. They are 0.5 and 0.7 Å shorter than the sums of van der Waals radii, respectively, and are the shortest C–I⋯As and C–I⋯Sb halogen bonds of this type found for experimentally characterized molecular (co)crystals. Comparisons of the packing motifs and contacts in 1 and 2 with those in (CH3)3As (3), (CH3)3Sb (4) and C6F5I (5) illustrate the occurrence and hierarchy of the specific interactions. The heteromolecular components in 1 and 2 are assembled by I⋯As, I⋯Sb and F⋯H interactions. There ar…
Crystalline gas of 1,1,1-trichloroethane
2011
Isobaric freezing of 1,1,1-trichloroethane yields crystals where all the intermolecular contacts are much longer than the sums of the van der Waals radii and only in the structure compressed to ca. 1.2 GPa do the first Cl⋯Cl contacts become commensurate with this sum. This sheds new light on the range of intermolecular interactions that are capable of controlling molecular re-orientation and arrangement.
Van der Waals Interactions in a Magneto-Dielectric Medium
2007
The van der Waals interaction between two ground-state atoms is calculated for two electrically or magnetically polarizable particles embedded in a dispersive magneto-dielectric medium. Unlike previous calculations which infer the atom-atom interaction from the dilute-medium limit of the macroscopic, many-body van der Waals interaction, the interaction is calculated directly for the system of two atoms in a magneto-dielectric medium. Two approaches are presented, the first based on the quantized electromagnetic field in a dispersive medium without absorption and the second on Green functions that allow for absorption. We show that the correct van der Waals interactions are obtained regardle…
Electrochemical properties of crystallized dilithium squarate: insight from dispersion-corrected density functional theory.
2012
International audience; The stacking parameters, lattice constants, and bond lengths of solvent-free dilithium squarate (Li(2)C(4)O(4)) crystals were investigated using density functional theory with and without dispersion corrections. The shortcoming of the GGA (PBE) calculation with respect to the dispersive forces appears in the form of an overestimation of the unit cell volume up to 5.8%. The original Grimme method for dispersion corrections has been tested together with modified versions of this scheme by changing the damping function. One of the modified dispersion-corrected DFT schemes, related to a rescaling of van der Waals radii, provides significant improvements for the descripti…
Relations between the cohesive energy, atomic volume, bulk modulus and sound velocity in metals
2011
By analysing the experimental data available in the literature, it has been found that the bulk modulus B of metals is proportional to the cohesive energy density Ec/V. For metals which start to melt having the close packed structure A1 or A3 the proportionality factor in the forementioned correlation is distinctly greater than that for metals melting from the A2 type structure. The existence of the correlation between the bulk modulus and the cohesive energy density leads to another, hitherto unrevealed correlation between the sound velocity, cohesive energy and the molar mass of metals: u2 ~ Ec/μ.