Z. A. Matysina

Hydrogen in fullerites

The peculiar kind of fullerene molecule structure is also reflected in the crystal structure of fullerites. The cubic lattices of metal fullerides and hydrofullerenes behave similarly to the cubic lattices of different metals and alloys. They form interstitial solid solutions when impurity elements are distributed in octahedral and tetrahedral interstitial sites. By replacement of C60 and C70 molecules in lattice sites they make up substitution solid solutions. Forming exo- and endohedral compounds, the fullerene molecules, located in sites of the crystal lattice, can modify greatly the crystal properties with no change of crystalline structure. Some peculiarities of fullerite crystalline structures will be discussed in the present paper.

Surface structure, roughness, energy and texture of crystals

Abstract The energy of the boundary between crystal and melt is calculated in a quasi-chemical approximation taking into consideration the correlation in the substitution of lattice sites by the atoms and the atomic interaction anisotropy. The molecular roughness of the interface is determined. The influence of correlation and anisotropy on the crystal surface roughness is ascertained. The numerical analysis for bismuth permitted one to obtain some information about the atomic interaction in solid, liquid and different phases. The energy of different lattice sites planes of monocrystals was calculated using the broken bonds method and its angular relation defined. The calculations are carried out for relative surface energies of lattice site planes which make up the various angles with plane (0001) of Be, Hf, Ti, Zr, Mg, Co, Zn and Cd monocrystals. A comparison between theoretical calculations and experimental data is carried out.

Hydrogen in lanthan-nickel storage alloys

Abstract A theoretical study of hydrogen solubility in lanthan–nickel storage alloys of D2d structure and CaZn 5 type was carried out taking into account the possible arrangement of hydrogen atoms in interstitial sites of two types. The equilibrium state equation determining the P – T – c diagram was determined and hydrogen solubility isotherms were constructed. The calculation results were compared with experimental data for hydrogen solubility in binary LaNi 5 , LaCu 5 and LaCo 5 alloys and various ternary phases of the examined structure.

The peculiarities of carbon interaction with catalysts during the synthesis of carbon nanomaterials

Abstract Catalysts based on metals of the iron group (Fe, Ni, Co) and their alloys are used in different methods of carbon nanomaterial production. The selection of optimal regimes for these processes calls for fundamental consideration of processes on the catalyst. An investigation of the distribution and thermally activated redistribution of interstitial carbon atoms in the volume and surface of crystalline films has been carried out. These crystals have a b.c.c. lattice and various types of free facets. The kinetic curves of interstitial atom redistribution under changes of temperature have been studied. Correlation has been made between theoretical calculations and experimental data for the graphitization of Fe–C, Ni–C, Co–C alloys and Fe–C alloy with V, Cu, Ti, Co or Ni impurities. The energetic conditions and possibility of macroscopic surface segregation of interstitial atoms have been established.

The surface energy of crystalline CuZn and FeAl alloys

Abstract The computer-aided calculation of the surface energy of disordered and completely ordered CuZn and FeAl alloys is performed. The broken-bond method and the stepped microrelief model of crystal faces are used in the calculations. The computations are based on the molecular-kinetic theory.

Impurities in Ni3Fe magnetic alloys

Abstract The theoretical—in terms of the classical theory of ordering—and the experimental—with neutron diffraction analysis—investigations of the influence of the third component impurities on structural and magnetic ordering of Ni 3 Fe alloys have been carried out. Comparison of theoretical results with the experimental data, revealing the effect of the third component impurities of W, Mo, Cr and Mn atoms on the degree of atomic ordering and magnetization in Ni 3 Fe binary alloys, on order-disorder and Curie temperatures, and on the interrelation between atomic and magnetic ordering phenomena, shows good qualitative agreement between theory and experiments for all the systems chosen.

Hydrogen solubility in alloys under pressure

The influence of external pressure on the solubility of interstitial impurities in alloys has been investigated. The thermodynamic potential of the system has been calculated, allowing for the change, due to pressure, in crystal volume, lattice parameter, interstitial atom activity and therefore in impurity atom energies determined by the sum of interaction energies between interstitial atoms and the nearest matrix atoms. The cause of the non-linear solubility dependence on pressure has been ascertained. The possible change of the dependence character of hydrogen solubility on pressure at the expense of magnetic and other phase transformations has been identified.

The solubility of interstitial impurities

Abstract A theoretical investigation on the solubility of interstitial impurities in alloys with various crystalline structures was carried out. Comparison of the theoretical results with the experimental data on the concentration and temperature dependence of hydrogen, oxygen and carbon solubility shows good agreement between theory and experiment for PdPt-H, PdNi-H, FeV-H, Ni 3 Fe-H, AgAu-O and FeNi-C alloys.

THE SPECIAL FEATURES OF FORMATION OF CARBON NANOSTRUCTURES, THEIR CLASSIFICATION AND SITE ON THE STATE DIAGRAM OF CARBON

The peculiarities of possible formation of low-temperature carbon structures (fullerite F, crystalline carbyne CC, nanotubes crystals NTC) in the area of graphite G realization in the state diagram P-T have been described in the present paper. In addition, the regions of existence of high-temperature structures (molecular carbyne C, graphene Gr, molecules of nanotubes NT, fullerene molecules Fn, pent- and sixatomic cyclic molecules) in the area of gaseous carbon have been marked.

Hydrogen-sorption properties of magnesium and its intermetallics with Ca7Ge-Type structure

The statistical theory of the hydrogenation of magnesium and its alloys Mg6M′M″(with M′ = Mg, Ti, V, Nb, Zr; M″ = Mg, Al, Zn) has been developed. The energies of crystals have been calculated, and equations for their thermodynamic equilibrium state have been found. Equations for determining the P-T-c diagram have been obtained. Curves that determine the temperature dependences of the concentration of hydrogen desorbed from crystals were studied. The maximum hydrogen-desorption temperature and its dependence on interatomic-interaction energy parameters and the activity of hydrogen atoms were estimated. Isopleths of hydrogen solubility were calculated for different concentrations of hydrogen. The level of the curves for different coefficients of activity and slope for different hydrogen contents were found. Isotherms of hydrogen solubility in crystals were studied. The possibility of achieving the sorption hysteresis effect was clarified, and the length and width of the hysteresis loop at different temperatures were estimated. The aforementioned functional dependences were plotted. The calculated data were compared with experimental results available in the literature. The theoretical and experimental data agree qualitatively.