Dielectric and13C NMR studies of sulfur dioxide-hydroquinone clathrates

Dielectric measurements of SO₂ quinol clathrates show that the reorientation of encaged SO₂ molecules is very rapid and depends greatly on the degree of cage occupancy. For a-quinol sample of cage occupancy = 0.57, the reorientation rate was 1 MHz at 6 K, with a reorientational activation energy of 673 J/mol. For a sample identified by¹³C NMR as-quinol, and for a-quinol sample with most cages filled with Xe, SO₂ reorientation rates are even greater, with activation energies of only some tens of J/mol. The low temperature dielectric studies show that some ethanol may be enclathrated in-quinol recrystallized from this solvent. The¹³C NMR spectra confirm the X-ray results that the lattice becomes distorted with increased SO₂ content.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

Heat capacity and glass transition of ethylene oxide clathrate hydrate

The heat capacity of structure I ethylene oxide clathrate hydrate EO-6.86 H₂O was measured in the temperature range 6–300 K with an adiabatic calorimeter. The temperature and enthalpy of congruent melting were determined to be (284.11 ± 0.02) K and 48.26 kJ mol^–1, respectively. A glass transition related to the proton configurational mode in the hydrogen-bonded host was observed around 90 K. This glass transition was similar to the one observed previously for the structure II tetrahydrofuran hydrate but showed a wider distribution of relaxation times. The anomalous heat capacity and activation enthalpy associated with the glass transition were almost the same as those for THF-hydrate.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.Author for correspondence.     

Lattice dynamics study of low energy guest-host coupling in clathrate hydrate

Our lattice dynamics simulation of Xe-hydrate with four-site TIP4P oxygen-shell model can accurately reproduce each peak position in the inelastic incoherent neutron scattering spectrum at the acoustic band （below 15 meV） and yield correct relative intensity. Based on the results, the uncertain profile at ～6 meV is assigned to anharmonic guest modes coupled strongly to small cages. Blue shift is proposed in phonon dispersion sheet in the case of anticrossing and found to be an evident signal for guest-host coupling that explains the anomalous thermal conductivity of clathrate hydrate.     

Study of the Deflection Angle and Shadow of Black Hole Solutions in Non-Plasma and Plasma Mediums Under the Effect of Einstein–Gauss–Bonnet Gravity

In this paper, the Gibbons and Werner technique is used to calculate the weak deflection angle for the black hole solution under the effects of Einstein–Gauss–Bonnet gravity. The Gauss–Bonnet theorem in the limits of weak field is used to evaluate the Gaussian optical curvature in order to obtain the results. The visual effects of the deflection angle on the impact parameter is also looked at and the smallest radius in the non-plasma/plasma medium. Moreover, in order to check the consistency of the results concerning the weak deflection angle, the Keeton and Petters approach is applied to study the deflection angle, which is the expansion of series with a single mass variable, which can be directly addressed by using the post–post Newtonian framework. Furthermore, the deflection angle and shadow under the influence of the plasma is examined by using the motion of particle in a non-magnetized plasma and pressure-free plasma medium as described by the new ray-tracing algorithm. It is shown that plasma as well as Einstein–Gauss-Bonnet gravity corrections are affected by shadows.     

Structural study of the 1:1 clathrate of an asymmetric calix[4]arene and acetone

The crystal and molecular structure of the 1:1 clathrate of the asymmetric calix[4]arene,1, and acetone has been determined by X-ray analysis. The crystal data are: tetragonal, space groupP4/n,a=b=12.574(6),c=12.572(6) Å,V=1988(2) ų,Z=2,D _x =1.111 g cm^–3,D _m =1.108 g cm^–3. Least-squares refinement based on 1131 observed reflections withF ₀>3(F ₀) and anisotropic temperature factors led toR=0.096. In spite of the molecular asymmetric calixarene1 the crystal structure has high symmetry, because a part of the host and guest molecules are in disordered states.     

Gas Hydrate Frameworks of Allen's Polyhedra. 3. Chemical and Structural Implications of the Topological Properties of the Frameworks

The topology of frameworks of 5¹²(D), 5¹²6² (T) 5¹²6³ (P), and 5¹²6⁴ (H) polyhedra, belonging to the most widespread class of gas hydrate frameworks, is discussed. The frameworks of formula (D₃T₂P₂)_x (D₄H₂)_y (D₂T₆)_z, where x, y, and z are integers, have low strain energies of hydrogen bonds. For these frameworks, formulas relating their topological characteristics (the number of water molecules and hydrogen bonds in the unit cell, etc.) to x, y, and z are given. The tendencies of variation of hydration numbers in clathrate and semiclathrate hydrates are considered. Compounds with new structures of water frameworks are predicted, and approaches to selection of possible chemical systems with such compounds are discussed. The structural regularities found for the frameworks and the relationships between their topological characteristics may be used for analyzing Frank–Kasper structures of intermetallic compounds that are dualists of the polyhedral frameworks under study.     

The Intermetallic Type-I Clathrate Na8Zn4Ge42

The new intermetallic type-I clathrate Na₈Zn₄Ge₄₂ was obtained by direct reaction of the elements, and its crystal structure was determined by means of single-crystal X-ray diffraction methods. The structure is described in space group Pm3 n (no. 223) with a = 10.6982(1) Å. A mixed Zn/Ge occupancy is found for one of the network sites (6c). Na₈Zn₄Ge₄₂ represents an air-stable electron-precise Zintl phase with exclusively Na cations located in the cavities of a polyanionic host network of four-connected Zn and Ge atoms.     

An infrared and Raman spectroscopic study of Td-type 4,4′-bipyridylcadmium(II) tetracyanometallate (II) benzene (1/2) clathrates: Cd(C10H8N2)Cd(CN)4 · 2C6H6 and Cd(C10H8N2)Hg(CN)4 · 2C6H6

Two new benzene clathrates of the form Cd(4,4-bipyridyl)M(CN)₄ · 2C₆H₆, (M=Cd or Hg) have been prepared in powder form. Their spectral data were compared with those of the corresponding host complexes and found to be consistent with the host structure found in Td-type clathrates.