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X-ray diffraction has been used to study the phase composition and determine the lattice parameter of the β- and α-phases in foil of a Pd–Cu solid solution with a composition that ensures reversibility of the β $$ \rightleftarrows $$ α transformations: with the structure of the β- and α-phases and a two-phase structure. The thermal expansion coefficient of the Pd–Cu solid solution has been determined for the first time.

We have studied the phase composition and texture of a Pd–Cu solid solution with a nearly equiatomic composition in different steps of the preparation of membrane foil by rolling to 300, 175, 100, and 20 μm and 7-μm-thick foil produced by magnetron sputtering of a target having the same composition as the foil. We have identified orientation relationships between the β- and α-phases in the as-prepared two-phase structures and demonstrated that, after heating to 600°C and subsequent cooling, the ordered solid solutions (β-phase) prepared by the two processes, have identical textures, which can be understood in terms of the transformation mechanism.

The effectiveness of flash lamp processing and ion beam sputtering in surface cleaning of membrane foil from a Pd–Cu solid solution produced by rolling has been assessed using cyclic voltammetry and atomic force microscopy. It has been shown that it is reasonable to use cyclic voltammetry for assessing the degree of foil surface cleaning and that combined surface processing of membrane foil is effective in foil surface cleaning. Ion beam processing reproducing the surface elemental composition corresponding to the original composition of the solid solution and increasing surface roughness is a factor of 1.3 more effective than combined surface processing.

The β $$ \rightleftarrows $$ α phase transformations in foil of the Pd–52 at % Cu solid solution prepared by rolling have been studied using X-ray diffractometry and resistivity measurements during thermal heating–cooling cycles or lamp processing (LP) using light from high-power pulsed xenon lamps, followed by cooling. The results demonstrate that complete ordering of the two-phase (α + β) as-prepared (as-rolled) foil follows the sequence (α + β) → β → α → β in the first heating–cooling cycle and β → α → β in the second and subsequent cycles. When a radiative energy critical for a given thickness of foil with an ordered structure is delivered to the foil surface, an irreversible β → α phase transformation occurs, whose rate can be three orders of magnitude higher than the rate characteristic of the disordering process during Joule heating. After LP, the reversibility of the β $$ \rightleftarrows $$ α phase transformations, inherent in the initial, ordered structure, is observed in a second thermal cycle: heating to 700°C and cooling. The sequence of phase transitions is α → β → α → β in the first cycle and β → α → β in the second and subsequent cycles. The localization of light in the skin layer and finite thermal conductivity offer the possibility of producing a structure with a phase composition gradient at subcritical irradiation times. The fact that the LP-stabilized α-phase persists up to 300°C makes it possible to compare the mechanical properties of foil samples having identical elemental compositions but different (ordered and disordered) structures.

In accordance with the orientation ratio (110), [001]β || (111), [$$1\bar {1}0$$]α established by fast electron diffraction between the ordered (β) and disordered (α) phases in the foil of a Pd + 57 at % Cu solid solution, the atomic structure of the interface is modeled by molecular dynamics. It is found that the structural and size discrepancies are compensated by interfacial dislocations with Burgers vectors a/2〈111〉 in coordinates of the β-phase.

В настоящей работе представлена новая методика построения решетки совпадающих узлов для кристаллов простой кубической, ОЦК, ГЦК структур, имеющих моноэлементные и полиэлементные составы. Разработан метод нахождения атомов различных элементов в межкристаллитных границах на основе специально построенной кристаллографической группы. Указаны возможные элементные составы специальных межкристаллитных границ, зарядовые состояния сопрягающихся плоскостей ЛИТЕРАТУРА1. Bollmann W. On the geometry of grain and phase boundaries // Phil. Mag., 1967, v. 16(140), pp. 363–381.DOI: https://doi.org/10.1080/147864367082297482. Bollmann W. On the geometry of grain and phase boundaries // Phil. Mag., 1967, v. 16(140), pp. 383–399.https://doi.org/10.1080/147864367082297493. Grimmer H. A method of determining the coincidence site lattices for cubic crystals // Acta Cryst. A,1974, v. 30(2), pp. 680–680. DOI: https://doi.org/10.1107/s056773947400163x4. Grimmer H., Bollmann W., Warrington D. T. Coincidence-site lattices and complete pattern-shiftin cubic crystals // Acta Cryst. A, 1974, v. 30(2), pp. 197–207. DOI : https://doi.org/10.1107/s056773947400043x5. Орлов А. Н., Перевезенцев В. Н., Рыбин В. В. Границы зерен в металлах. М.: Металлургия, 1980, 224 с.6. Глейтер Г., Чалмерс Б. Большеугловые границы зерен. М.: Мир, 1975, 376 с.7. Страумал Б. Б., Швиндлерман Л. С. Термическая стабильность и области существования специальных границ зерен // Поверхность. Физика, химия, механика, 1986, т. 10, с. 5–14.8. Fortes M. A. Coincidence site lattices in noncubic lattices // Phys. Stat. Sol. B, 1977, v. 82(1).pp. 377–382. DOI: https://doi.org/10.1002/pssb.22208201439. Bonnet R., Durand F. A general analytical method to fi nd a basis for the DSC lattice // ScriptaMet., 1975, v. 9(9), pp. 935–939. DOI: https://doi.org/10.1016/0036-9748(75)90548-710. Bonnet R. Note on a general analytical method to fi nd a basis for the DSC lattice. Derivation of a basisfor the CSL // Scripta Met., 1976, v. 10(9), pp. 801–806. DOI: https://doi.org/10.1016/0036-9748(76)90297-011. Bonnet R., Cousineau E. Computation of coincident and near-coincident cells for any two lattices– related DSC-1 and DSC-2 lattices // Acta Cryst. A, 1977, v. 33(5), pp. 850–856. DOI: https://doi.org/10.1107/s056773947700205812. Рыбин В. В., Перевезенцев В. Н. // ФТТ, 1975,т. 17, c. 3188–3193.13. Андреева А. В., Фионова Л. К. Анализ межкристаллитных границ на основе теории решетоксовпадающих узлов // ФММ, 1977, т. 44, с. 395–400.14. Кайбышев О. А., Валиев Р. З. Границы зерен и свойства металлов. М.: Металлургия, 1987, 214 c.15. Копецкий Ч. В., Орлов А. Н., Фионова Л. К. Границы зерен в чистых материалах. М.: Наука, 1987,160 c.16. Бокштейн Б. С. Структура и свойства внутренних поверхностей раздела в металлах. М.: Металлургия, 1988, 272 с.17. Kobayashi S., Tsurekawa S., Watanabe T. A new approach to grain boundary engineering for nanocrystallinematerials // Beilstein J. Nanotechnol., 2016, v. 7, pp. 1829–1849. DOI: https://doi.org/10.3762/bjnano.7.17618. Сухомлин Г. Д. Специальные границы в феррите низкоуглеродистых сталей // Металлофизика, новейшие технологии, 2013, т. 35, с. 1237–1249.19. Watanabe T. Grain boundary engineering: historical perspective and future prospects // Journalof Materials Science, 2011, v. 46, pp. 4095–4115. DOI: https://doi.org/10.1007/s10853-011-5393-z20. Waser R. Electronic properties of grain boundaries in SrTiO3 and BaTiO3 ceramics // Solid State Ionics,1995, v. 75, pp. 89–99. DOI: https://doi.org/10.1016/0167-2738(94)00152-i21. Daniels J., Wemicke R. New Aspects of an Improved PTC Model // Philips Res. Rep., 1976, v. 31,pp. 544–559.22. Vikrant K. S. N., Edwin G. R. Charged grain boundary transitions in ionic ceramics for energy applications// Computational Materials, 2019, v. 5(1), pp. 24. DOI: https://doi.org/10.1038/s41524-019-0159-223. Kim M., Duscher G., Browning N.D., Sohlberg K., Pantelides S. T., Pennycook S. J. Nonstoichiometryand the electrical activity of grain boundaries in SrTiO3 // Physical Review Letters, 2001, v. 86,pp. 4056–4059. DOI: https://doi.org/10.1103/physrevlett.86.405624. Oyama T., Wada N., Takagi H. Trapping of oxygen vacancy at grain boundary and its correlationwith local atomic confi guration and resultant excess energy in barium titanate: A systematic computationalanalysis // Physical Review B, 2010, v. 82, pp. 134107. DOI: https://doi.org/10.1103/physrevb.82.13410725. Duffy D.M., Tasker P.W. Space-charge regions around dipolar grain boundaries // Journal of AppliedPhysics, 1984, v. 56, pp. 971–977. DOI: https://doi.org/10.1063/1.33403726. Даринский Б. М., Ефанова Н. Д., Прижимов А. С. Систематика решеток совпадающих узловдля ОЦК и ГЦК кристаллов // Конденсированные среды и межфазные границы, 2018, т. 20(4), с. 581–586. DOI: https://doi.org/10.17308/kcmf.2018.20/632

В настоящей работе предложена новая методика построения решетки совпадающих узлов для ОЦК и ГЦК кристаллов. Получены условия образования орторомбической, тетрагональной и кубической решетки совпадений и указаны конкретные решетки этих сингоний. Показаны возможные поликристаллические структуры, имеющие общую решетку совпадающих узлов.

Hydrogen diffusion in palladium bicrystals containing a small-angle twist or tilt boundary or a large-angle boundary similar to a special boundary is investigated using molecular dynamics simulation. We assess the effect of grain boundaries on the hydrogen diffusion process. The types of grain boundaries considered here are shown to differ in their absorption activity for hydrogen. The temporal grain-boundary segregation of hydrogen atoms can be accounted for in terms of their coordination, which differs significantly from that in the grain bulk.

The object of this study is polycrystalline materials containing intercrystalline boundaries as one of the accompanying components of the defective structure. A wide variety of geometric characteristics that determine the atomic structure and physical properties of intergranular boundaries, gives rise to the expediency of systematization of the entire set of possible intergranular boundaries. The intercrystalline boundaries obtained on the basis of the coincidence of nodes are an important family of defects in polycrystals, so these defects are given a lot of research, but currently there is no complete systematization. The construction of such systematization was the purpose of this paper. The basis of classification is the coordination polyhedron of the simple cubic lattice. Seven different polytopes with different topological characteristics are given. As parameters defining the geometry of the lattice matching of the nodes of the selected pair of vectors the vertices of these polyhedra and the lattice vector that defines the axis of rotation was used. Using algebraic methods used in studies of solid rotation, formulas are obtained for the crystallographic plane in which all possible axes of turns and vectors of the lattice cell of matching nodes should lie. As a result, it was shown that the coincidence lattices of General form belong to monoclinic crystal structure. In particular cases they may belong to orthorhombic and tetragonal crystal structure. It is shown that such lattices of coinciding nodes are possible, which are obtained at different parameters of rotation, so polycrystals on the basis of the common lattice of coincidences are possible. A table is constructed in which the data are systematized for the vectors of the cell of the lattice of coincidences, rotation angles, the number of atoms in the cell at different initial characteristics of rotation. ACKNOWLEDGMENTS The work was carried out within the framework of the state task of the Ministry of Education and Science of Russia to higher educational institutions and scientific organizations in the field of scientific activity (project No. 4.7972.2017 / 8.9).

The present review details the results of studies that showcase the capacity of the molecular dynamics method to analyze the atomic structure of small-sized metallic objects: nanoparticles, thin films, and film heterostructures.

The specific features of the heteroepitaxial growth of Cu-Pd solid solution films on the (001) surface of a Pd crystal at temperatures of 600 and 1000 K have been investigated using the molecular dynamics simulation. The condensation from a two-component flow has been simulated by a sequential deposition of Cu and Pd atoms with concentrations of 60 at % Cu and 40 at % Pd by portions of 0.1 ML, which corresponds to an effective deposition rate of ∼3.3 × 109 ML/s. It has been established that there is a coherent conjugation of the crystal lattices of the film and the substrate. The growth is accompanied by the formation of an intermediate solid solution monolayer phase: the phase is formed in the first layer of the film at a temperature of 600 K and in the upper layer of the substrate at 1000 K.

The structure of an fcc(001)/fcc(001) interphase boundary in a “nickel hemispherical crystal nanoparticle-palladium crystal substrate” system is investigated using molecular dynamics simulation with multiparticle potentials calculated in the framework of the embedded-atom method as a function of the angle of rotation of the nanoparticle. Relaxation transformations are found to occur in a component of the system under investigation with a larger lattice parameter. It is demonstrated that, under given annealing conditions, the system is characterized by a size dependence of the angle of rotation of a nanoparticle: the annealing leaves the location of large islands virtually unchanged but brings about a rotation of small nanoparticles into a parallel orientation or an orientation with a local energy minimum.

Molecular-dynamics simulation based on many-particle potentials calculated in terms of the embedded-atom method was performed to study growth of Ni films on singular (001), (110), and (111) surfaces of a Pd single crystal at a temperature T = 1000 K. Upon the growth of a Ni film on (001)Pd and (110)Pd surfaces, there is formed a heterostructure consisting of a Pd substrate, a single-layer epitaxially stabilized solidsolution phase, and a film of an Ni-Pd solid solution. At the initial stages of the film growth, the lattice misfit is compensated via elastic deformation; with increasing average thickness of the film, there occurs a relaxation of the elastic deformation: in the (001)Pd-Ni heterosystem, via the formation of misfit dislocations; in the (110)Pd-Ni heterosystem, via misfit dislocations and point defects (in the [\(1\bar 10\)] direction) as well as via partial dislocations (in the [001] direction). Upon the growth of an Ni film on the (111)Pd surface, no intermixing of the components occurs; already at the initial stages of growth, the islands (clusters) are not deformed; the matching at the interphase boundary is incoherent.

The structure of the (001) fcc/(001) fcc interphase boundary of a system consisting of a hemispherical Ni (or Cu) crystal nanoparticle and a Pd crystal substrate was studied depending on the nanoparticle rotation angle θ = 15°, 20°, 25°, and 30°. A molecular dynamics simulation including multiparticle potentials calculated in the framework of the embedded atom method was used in this study. It was shown that, under given annealing conditions, the nanoparticle rotation depends on the size; namely, the annealing of small nanoparticles leads to their rotation to the position corresponding to the coincidence orientation at the interphase boundary, while the position of large islands remains practically unchanged. It was established that the atomic rearrangement at the interphase boundary affects only lattices with a larger parameter.