The relaxational changes of me electrical capacitance of a system of grains poured abruptly into a vessel capacitor have been observed. Two power-law decays have been found. The faster relaxation at the beginning has been interpreted as being driven by independent-grain motion. The later slower process has been ascribed to the collective reorganization of the, granular system. The observations seem to be an experimental illustration of the computer simulation predictions of Mehta and Barker [Rep. Prog. Phys. 57, 383 (1994); Phys. Rev. A 45, 3435 (1992); Phys. Rev. Lett. 67, 394 (1991); Nature 364, 486 (1993); Phys. Rev. E 47, 184 (1993)].

The results of a large inelastic neutron scattering (INS) experiment performed for different kinds of the dispersed silicas are presented. The amplitude weighted density of states (AWDS) spectra are obtained from the INS spectra recorded at 10, 80 and 290 K. The two aerosil samples differing twice in specific areas (A380 and A175) as well as the two silica gels with the pore size of 20 and 100 Å (SG20 and SG100) are studied. The results obtained for the “A380-family” of samples consisting of aerosil A380 equilibrated with light and heavy water at relative humidity of 60–70%, dried at 700°C and sintered at 1200°C allowed to separate their AWDS spectra into the siloxan core spectra and spectra of the OH + H2O, H2O and OH shells. These sorts of spectra are got for the silica gels. The AWDS spectra for the aerosils and the silica gels are quite different indicating a big difference in the structure of cores and shells of both the silicas as well as in the water molecule arranging on them. The possibility to tackle the results in terms of the computation chemistry is discussed.

Neutron scattering investigations under high pressure (h.p.) give qualitatively new information about studied materials, especially on the pressure induced changes in the structure and dynamics. Making use of the experimental facilities at the IBR-2(1) pulsed reactor, a h.p. setup has been successfully created. Gaseous helium has been chosen as a pressure transmitting medium to allow experiments down to a few Kelvin with 0.1 < p < 400 MPa.

The inelastic neutron scattering (INS) and neutron diffraction (ND) spectra from the H x YBa 2 Cu 3 O 7 superconducting ceramics (x= 0.05, 0.20, 0.60) are investigated at 290, 80 and 10 K. Vibrational spectra of hydrogen atoms show three wide bands at about 10, 28 and 85 meV. Intensities of them are proportional to the hydrogen concentration. From the temperature behaviour of the INS spectra and from the X-ray and ND results for different hydrogen concentrations we can conclude that this bands correspond to an amorphous, not superconducting precipitations which are formed during hydration of Y-123 superconducting ceramics. From the concentration dependence of the INS spectra we can conclude that the solubility of hydrogen in Y-123 superconducting phase is in order of few percent. It seems that H atoms in solid solution are located in the octahedral position formed by four Y and two Cu(2) atoms.