Powder x-ray diffractometry was used to study the effect of intercalating C60 fullerite with helium and argon atoms on the fullerite structure. The samples were saturated at room temperature and normal pressure. The dependences obtained for the lattice parameter and half-width of certain reflections on the intercalation time with helium atoms showed that the voids in the C60 lattice were filled in two stages. Helium filled the octahedral voids relatively rapidly first and then the tetrahedral subsystem, but much more slowly. Both intercalants affected the half-width and intensity of the reflections, the matrix lattice parameters, the phase transition temperature, the volume jump at the transition, and the thermal expansion coefficients of C60 fullerite.
X-Ray investigations of vacuum condensates of the binary mixtures Ne–nD2 at temperatures from 6 K to the melting point of the solutions are performed. A diagram of phase equilibrium of the liquid and solid mixtures is proposed on the basis of the experimentally obtained and published data on the phase composition and mutual solubility of the components. The isotopic effect in the mutual solubility of the components is determined. A long-lived but metastable hexagonal phase is found, and the conditions for the formation and decomposition of this phase are determined.
X-Ray investigations of solid solutions formed by condensation of mixtures of normal hydrogen and neon gases are performed for concentrations ranging from 2 to 60 mol.% nH2 and temperatures ranging from 5 K to the melting temperature of the sample. The structure of the vacuum condensates Ne-nH2 immediately after the samples are obtained is investigated. The boundary of single-phase solutions of hydrogen in neon is established to be 2 mol.%. At high H2 concentrations a hexagonal hcp2 phase forms in addition to a cubic fcc phase. The lattice volumes of these phases are somewhat larger but close to the volume of a pure-neon cell. The hexagonal hcp2 phase vanishes when the condensates are heated to a temperature of the order of the melting temperature of neon. This metastable hexagonal phase in the neon-rich mixtures studied is probably identical in nature to the previously observed hcp2 phase in hydrogen-rich solid mixtures. Both phases have one symmetry and the same cell volume. Information on the phase composition of the condensates is obtained from data on the concentration and temperature variations of the x-ray reflection intensities. It is shown that as the concentration of hydrogen molecules in the initial gas mixtures increases, the amount of the fcc phase in the condensates decreases almost linearly and the amount of the hcp2 phase increases. A combined analysis of the data obtained in the present work and previous measurements established the phase boundaries in the entire concentration range of the condensates. Evidently, because the molecular parameters of the components are close the Ne-nH2 mixtures do not form gel-like states, which are characteristic for quench-condensed Kr–H2 condensates.
Articles you may be interested inVoids and Mn-rich inclusions in a (Ga,Mn)As ferromagnetic semiconductor investigated by transmission electron microscopy The structure of the cryoalloys CO 2 -Kr has been studied in the entire range of relative concentrations by means of transmission electron diffraction. Gaseous samples were deposited from a tank at room temperature onto substrates cooled to 30 K. The filling channel was thermally insulated from the cryogenic screens. An anomalous dependence of the lattice parameter a on the molar content x of krypton in the initial gas mixture was observed; specifically, the function a͑x͒ contains a section which can be regarded as a minimum to within the limits of error. The maximum solubility of the krypton in the carbon dioxide crystal is 38 mol. %, and the solubility of CO 2 in a Kr crystal is low. The experimental data taken together give us a basis for supposing that the phase composition as a function of x has the following regions: 1͒ 0 ഛ x ഛ 0.38-regular solution of Kr in CO 2 ; 0.38ഛ x ഛ 0.6-mixture of a regular solution with critical concentration x cr = 0.38 and nano inclusions of almost pure Kr; 3͒ 0.6ഛ x ഛ 1-mixture of almost pure Kr with nano inclusions of a solution with x cr . A theoretical explanation is given for the anomalous behavior of the function a͑x͒ for x Շ 20 mol. %; the explanation is based on a cluster model and takes account of three mechanisms of interaction of Kr clusters with the crystalline environment of CO 2 . FIG. 1. Electron diffraction patterns of the solid mixtures CO 2 -Kr on a substrate consisting of amorphous carbon at T = 30 K: 2.5 mol. % Kr ͑a͒; 10 mole % Kr ͑b͒; 59 mol. % Kr ͑c͒; 70 mol. % Kr ͑d͒. Low Temp. Phys. 36 ͑3͒, March 2010 Danchuk et al. 255
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