52 research outputs found
Stable crystalline lattices in two-dimensional binary mixtures of dipolar particles
The phase diagram of binary mixtures of particles interacting via a pair
potential of parallel dipoles is computed at zero temperature as a function of
composition and the ratio of their magnetic susceptibilities. Using lattice
sums, a rich variety of different stable crystalline structures is identified
including structures. [ particles correspond to large (small)
dipolar moments.] Their elementary cells consist of triangular, square,
rectangular or rhombic lattices of the particles with a basis comprising
various structures of and particles. For small (dipolar) asymmetry
there are intermediate and crystals besides the pure and
triangular crystals. These structures are detectable in experiments on granular
and colloidal matter.Comment: 6 pages - 2 figs - phase diagram update
Crystal nuclei and structural correlations in two-dimensional colloidal mixtures: experiment versus simulation
We examine binary mixtures of superparamagnetic colloidal particles confined
to a two-dimensional water-air interface both by real-space experiments and
Monte-Carlo computer simulations at high coupling strength. In the simulations,
the interaction is modelled as a pairwise dipole-dipole repulsion. While the
ratio of magnetic dipole moments is fixed, the interaction strength governed by
the external magnetic field and the relative composition is varied. Excellent
agreement between simulation and experiment is found for the partial pair
distribution functions including the fine structure of the neighbour shells at
high coupling. Furthermore local crystal nuclei in the melt are identified by
bond-orientational order parameters and their contribution to the pair
structure is discussed
Structural investigation of a new cadmium coordination compound prepared by sonochemical process: Crystal structure, Hirshfeld surface, thermal, TD-DFT and NBO analyses
The final publication is available at Elsevier via https://doi.org/10.1016/j.ultsonch.2018.11.024. © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/A new nanostructured cadmium complex containing a tridentate Schiff base ligand was sonochemically synthesized and characterized by XRPD, FT/IR, NMR, and single crystal X-ray crystallography. Structural data showed that cadmium(II) ion is surrounded by three nitrogen atoms of Schiff base ligand and two iodide anions. The crystal packing was contained the intermolecular interactions such as CH⋯O, CH⋯I and π⋯π interactions organizing the self-assembly process. Hirshfeld surfaces and corresponding fingerprint plots have been used for investigation of the nature and proportion of interactions in the crystal packing. FT/IR, NMR and XRD data were in agreement with the X-ray structure and confirm the phase purity of the prepared sample. The molecular structure of the complex was optimized by density functional theory (DFT) calculation at the B3LYP/LANL2DZ level of theory and the results were compared with experimental ones. For more concise study of structure and spectral aspects of the complex, natural bond orbital (NBO) analysis and time-dependent density functional theory (TD-DFT) have been also performed. Thermal stability of the cadmium iodide complex was investigated by thermogravimetric analysis (TGA). Finally, cadmium oxide nanoparticles was prepared by direct calcination of CdLI2 complex as a new precursor.Partial support of this work by Yasouj University is appreciated
Dynamical correlations and collective excitations of Yukawa liquids
In dusty (complex) plasmas, containing mesoscopic charged grains, the
grain-grain interaction in many cases can be well described through a Yukawa
potential. In this Review we summarize the basics of the computational and
theoretical approaches capable of describing many-particle Yukawa systems in
the liquid and solid phases and discuss the properties of the dynamical density
and current correlation spectra of three- and two-dimensional strongly coupled
Yukawa systems, generated by molecular dynamics simulations. We show details of
the dispersion relations for the collective excitations in these
systems, as obtained theoretically following the quasilocalized charge
approximation, as well as from the fluctuation spectra created by simulations.
The theoretical and simulation results are also compared with those obtained in
complex plasma experiments.Comment: 54 pages, 31 figure
Heterogeneous nucleation and microstructure formation: Steps towards a system and scale bridging understanding
Ionic mixtures in two dimensions: From regular to empty crystals
The ground state of a two-dimensional ionic mixture at zero pressure composed of oppositely charged spheres is determined as a function of the size asymmetry by using a penalty method. The cascade of stable structures includes square, triangular and rhombic crystals as well as “empty” crystals made up of dipoles and chains, which have a vanishing number density. Thereby we confirm the square structure, found experimentally on charged granulates, and predict new phases detectable in experiments on granular and colloidal matter
Structures and Physical Properties of New Semiconducting Polyselenides Ba2CudAg4-dSe5 with Unprecedented Linear Se34- Units
Not Too Big and Not Too Small: “Goldilocks” Anion Size for Three-Dimensional Metal–Organic Frameworks Containing Oligothiophene Dinitrile Ligands (C<sub>4</sub>H<sub>2</sub>S)<sub><i>n</i></sub>(CN)<sub>2</sub> (<i>n</i> = 1, 2, 3) Bridging Silver(I) Cations
A series of oligothiophene dinitriles,
containing one, two, or
three oligothiophene rings between nitrile donors NC-(C<sub>4</sub>H<sub>2</sub>S)<sub><i>n</i></sub>-CN are reacted with
silverÂ(I) salts to form coordination compounds. In most cases, the
resulting metal–organic frameworks are one-dimensional coordination
polymers containing roughly linear divalent AgÂ(I) centers. However,
in the case of bithiophene (<i>n</i> = 2) and terthiophene
(<i>n</i> = 3) bridges, a three-dimensional structure is
also possible if the silverÂ(I) counterion is just the right size to
fit into the diamondoid pores that form with four-coordinate tetrahedrally
oriented AgÂ(I) centers. Thus, only ClO<sub>4</sub><sup>–</sup> and BF<sub>4</sub><sup>–</sup> form three-dimensional structures
with the bithiophene-bridged ligands, while the larger CF<sub>3</sub>SO<sub>3</sub><sup>–</sup> and SbF<sub>6</sub><sup>–</sup> anions will support a three-dimensional structure for the terthiophene-bridged
ligand. Any counterion larger or smaller than the “just right”
size will result in the one-dimensional structure instead
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