Moving beyond the constraints of chemistry via crystal structure discovery with isotropic multiwell pair potentials

The rigid constraints of chemistry—dictated by quantum mechanics and the discrete nature of the atom—limit the set of observable atomic crystal structures. What structures are possible in the absence of these constraints? Here, we systematically crystallize one-component systems of particles interacting with isotropic multiwell pair potentials. We investigate two tunable families of pairwise interaction potentials. Our simulations self-assemble a multitude of crystal structures ranging from basic lattices to complex networks. Sixteen of the structures have natural analogs spanning all coordination numbers found in inorganic chemistry. Fifteen more are hitherto unknown and occupy the space between covalent and metallic coordination environments. The discovered crystal structures constitute targets for self-assembly and expand our understanding of what a crystal structure can look like.

2D atomic crystal molecular superlattices by soft plasma intercalation

Two-dimensional (2D) atomic crystal superlattices integrate diverse 2D layered materials enabling adjustable electronic and optical properties. However, tunability of the interlayer gap and interactions remain challenging. Here we report a solution based on soft oxygen plasma intercalation. 2D atomic crystal molecular superlattices (ACMSs) are produced by intercalating O2+ ions into the interlayer space using the plasma electric field. Stable molecular oxygen layer is formed by van der Waals interactions with adjacent transition metal dichalcogenide (TMD) monolayers. The resulting interlayer gap expansion can effectively isolate TMD monolayers and impart exotic properties to homo-(MoS2[O2]x) and hetero-(MoS2[O2]x/WS2[O2]x) stacked ACMSs beyond typical capacities of monolayer TMDs, such as 100 times stronger photoluminescence and 100 times higher photocurrent. Our potentially universal approach to tune interlayer stacking and interactions in 2D ACMSs may lead to exotic superlattice properties intrinsic to monolayer materials such as direct bandgap pursued for future optoelectronics.

Theoretical Substantiation of the Operational Properties of Automobile Parts Reinforced with Composite Coatings by the Method of Cluster Components

A number of parts of car systems and units in the process of operation are subject to intensive wear and fatigue processes, and therefore do not withstand the planned service life. An important reserve for increasing the reliability and efficiency of such equipment is the strengthening of the working surfaces of its parts with composite materials and coatings. This method of strengthening makes it possible, controlling the structure of composite materials and coatings, to form the necessary set of performance properties of parts to ensure the appropriate level of reliability and increase durability. However, this requires theoretical justification to establish a correspondence between the structure, composition, distribution of chemical elements applied to the parts of the composite coating and their performance properties, such as wear resistance, fatigue strength, etc. The purpose of this work is a theoretical justification for the use of the method of cluster components to determine and form a set of necessary performance properties that ensure reliable and efficient operation of parts of systems and units of cars. The article theoretically substantiates the operational properties of automobile parts hardened with composite coatings using the method of cluster components. By choosing certain sets of parameters, as well as varying the system of restrictions on them, it is possible to form a complex of operational properties of parts. To simplify the packing model for composite materials and coatings, it is assumed that fillers of different compositions have an isometric shape and the same size. A regular structure is proposed, corresponding to the packing of spheres of the same size. It is shown that such packings form lattices similar to atomic crystal structures. The dependences of the function of the properties of composite coatings on the content of each of the types of cluster components are revealed. The method of cluster components, describing changes in the properties of composite coatings from the ratio of components, makes it possible to control a set of operational properties and obtain high-quality coatings to increase the durability of parts of systems and vehicle units. As a result of the conducted researches it is offered to consider composite coverings and composite materials as the systems characterized by a certain complex of operational properties depending on filler content and regularity of structure. According to the theory of cluster components, the content of the component determines the parameters and properties of composite coatings and materials. The method of cluster components makes it possible to present a set of operational properties as an additive model of its components. The packaging of components in composite coatings and materials is represented by atomic crystal structures: simple cubic, volume-centered cubic, face-centered cubic and hexagonal densely packed. The implementation of the method of cluster components on the example of a binary system of components A and B is considered. The basic configuration in accordance with the approximations of the statistical ordering theory is chosen. The visual interpretation and physical content of a mixture of powders, components of composite coatings and materials, particles A and B are given. The configurational entropy and formation of cluster components of the intermediate composition AB along with the basic AA and BB are considered. Based on the π-theorem, a complete set of quasi-chemical reactions is outlined. For binary composite coatings and materials АСВ1-С the matrices of size and relative content of components are constructed, the quasi-chemical formalism of the method of cluster components and the law of active masses for volume-centered cubic lattice are used. This is taken into account when building functional models of operational properties. Their specification on the criterion of correctness is carried out.

Electrochemical polymerization of poly(aniline-o-anisidine) and its anticorrosion properties

A synthesis of bismuth selenide with a thickness of 3-4 nm on the surface of mica taken as a matrix was investigated using the gas-solid mechanism. Since discovery of two-dimensional atomic crystals of graphene in 2004, scientists have grown interested in exploring methods for synthesis of two-dimensional atomic crystal nanofilms. Among them, of particular interest are sulfides and transition metal selenides, such as molybdenum sulfide, tungsten selenide, bismuth selenide. Bismuth selenide possesses special thermoelectric, photoelectric properties, therefore there are wide possibilities for its use in such areas as thermoelectric devices, photosensitive elements, optical information keepers, etc. In this connection, there are many studies on the search for optimal methods for the synthesis of bismuth selenide. Each of the proposed methods has its own advantages and disadvantages. In the article, a variety of the recently used gas-liquid-solid mechanism (V-L-S) is used as a method for the synthesis of bismuth selenide. When using amorphous silicon dioxide as a matrix, the synthesized bismuth selenide is not uniform, and the synthesis process is uncontrollable. Therefore, in the work fluorinated gold mica was used as a matrix. The effect of temperature, gas feed rate on the size, shape and thickness of the film was investigated.

Preparation of two-dimensional atomic crystal nanofilm of bismuth selenide of a large area

A synthesis of bismuth selenide with a thickness of 3-4 nm on the surface of mica taken as a matrix was investigated using the gas-solid mechanism. Since discovery of two-dimensional atomic crystals of graphene in 2004, scientists have grown interested in exploring methods for synthesis of two-dimensional atomic crystal nanofilms. Among them, of particular interest are sulfides and transition metal selenides, such as molybdenum sulfide, tungsten selenide, bismuth selenide. Bismuth selenide possesses special thermoelectric, photoelectric properties, therefore there are wide possibilities for its use in such areas as thermoelectric devices, photosensitive elements, optical information keepers, etc. In this connection, there are many studies on the search for optimal methods for the synthesis of bismuth selenide. Each of the proposed methods has its own advantages and disadvantages. In the article, a variety of the recently used gas-liquid-solid mechanism (V-L-S) is used as a method for the synthesis of bismuth selenide. When using amorphous silicon dioxide as a matrix, the synthesized bismuth selenide is not uniform, and the synthesis process is uncontrollable. Therefore, in the work fluorinated gold mica was used as a matrix. The effect of temperature, gas feed rate on the size, shape and thickness of the film was investigated.