[en] An attempt is made to systematize the data on the relaxation characteristics of liquid alkali metals (Li, Na, and K), which were investigated based on neutron-scattering data with the application of the two-time memory function formalism.

[en] The microstructure of Li-N melts with nitrogen impurity contents of 1.3 and 3.5 at % has been investigated by neutron diffraction. The main microstructural characteristic of the material (total structure factor) and the partial structure factors of the melt components and the radial distribution functions of particles have been obtained. It is established that there is no prepeak in the structure factor of Li-N melts, which indicates the existence of clusters of a certain size in the melt. Analysis of the partial structural characteristics suggests the existence of nitrogen impurity in Li-N melts in the form of lithium nitride Li₃N

[en] The features of the microscopic structure, as well as one-particle and collective dynamics of liquid gallium in the temperature range from T = 313 to 1273 K, are studied on the p = 1.0 atm isobar. Detailed analysis of the data on diffraction of neutrons and X-rays, as well as the results of atomic dynamics simulation, lead to some conclusions about the structure. In particular, for preset conditions, gallium is in the equilibrium liquid phase showing no features of any stable local crystalline clusters. The pronounced asymmetry of the principle peak of the static structure factor and the characteristic “shoulder” in its right-hand part appearing at temperatures close to the melting point, which are clearly observed in the diffraction data, are due to the fact that the arrangement of the nearest neighbors of an arbitrary atom in the system is estimated statistically from the range of correlation length values and not by a single value as in the case of simple liquids. Compactly located dimers with a very short bond make a significant contribution to the statistics of nearest neighbors. The temperature dependence of the self-diffusion coefficient calculated from atomic dynamics simulation agrees well with the results obtained from experimental spectra of the incoherent scattering function. Interpolation of the temperature dependence of the self-diffusion coefficient on a logarithmic scale reveals two linear regions with a transition temperature of about 600 K. The spectra of the dynamic structure factor and spectral densities of the local current calculated by simulating the atomic dynamics indicate the existence of acoustic vibrations with longitudinal and transverse polarizations in liquid gallium, which is confirmed by experimental data on inelastic scattering of neutrons and X-rays. It is found that the vibrational density of states is completely reproduced by the generalized Debye model, which makes it possible to decompose the total vibrational motion into individual contributions associated with the formation of acoustic waves with longitudinal and transverse polarizations. Comparison of the heights of the low-frequency component and of the high-frequency peak in the spectral density of vibrational states also indicates a temperature of T ≈ 600 K, at which the diffusion type of one-particle dynamics changes to the vibrational type upon a decrease in temperature. It is demonstrated that the modified Einstein–Stokes relation can be derived using the generalized Debye model

[en] The frequency spectra of vibrations of Li atoms at temperatures of 22, 227, 397, and 557 deg. C and the lithium-hydrogen melt (98 at % ⁷Li, 2 at % H) at 557 deg. C have been obtained from the experimental neutron inelastic scattering data. On the basis of the frequency spectra, the temperature dependences of the mean-square displacement of Li atoms, the mean-square amplitudes of atomic vibrations, and the velocity autocorrelation function of atoms have been calculated. The speed of sound in liquid lithium has been estimated within the Debye model. The frequency spectra of lithium-hydrogen melt and solid lithium hydride are compared. A generalized frequency spectrum of vibrations of hydrogen atoms in lithium-hydrogen melt is obtained

[en] The characteristics of the tripoli porous structure have been investigated by small-angle neutron scattering (SANS). Tripoli is a finely porous sedimentary rock formed by small spherical opal particles. Its main component is aqueous silica SiO₂ · nH₂O (80–90%). Tripoli is widely used in practice as a working medium for sorption filters and in some other commercial and construction technologies. The shape of the experimental SANS curves indicates the presence of small and large pores in tripoli. The small-pore size was estimated to be ∼100 Å. The size of large pores turned out to be beyond the range of neutron wave vector transfers Q that are available for the instrument used; however, their size was indirectly estimated to be ∼(2000–2500) Å. The pores of both groups behave as surfacetype fractal scatterers with the fractal dimension D ∼ 2.2‐2.6. The densities of pores of these two groups differ by approximately three orders of magnitude (∼10¹⁶ and ∼10¹³ cm⁻³ for small and large pores, respectively); the fraction of large pores amounts to 70–80% of the total pore volume. The found pore characteristics (their densities, sizes, and relative volumes) are in satisfactory agreement (when a comparison is possible) with the absorption data.

[en] The quasielastic neutron scattering experiments on liquid lithium (at 500 K and 830 K) and lithium-hydrogen melt (99 at.% Li⁷ and 1 at.% H at 830 K) were performed with the DIN-2PI time-of-flight spectrometer (FLNP, JINR, Dubna). The characteristics of the diffusion mobility for particles comprising the liquids studied are extracted from the experimental results and analyzed with the help of the phenomenological and theoretical models. The self-diffusion coefficient in liquid lithium obtained for both temperatures is in the agreement with the one known in literature. The questions connected to hydrogen diffusion in the liquid lithium are discussed

[en] Neutron quasielastic scattering experiments on liquid lithium (at 500 and 830 K) and a lithium-hydrogen melt (99 at.% Li⁷ and 1 at.% H at 830 K) have been performed. The characteristics of the diffusion mobility for lithium and hydrogen atoms have been extracted from the experimental results and analyzed with the use of phenomenological and theoretical models. The self-diffusion coefficient in liquid lithium obtained for both temperatures is in agreement with values in the literature. The mechanism of hydrogen diffusion mobility in liquid lithium is discussed. It has been concluded that the hydrogen in the liquid lithium exists and diffuses in the form of the hydride LiH