What Is Metallic Bonding?

Synthetic metals A class of compounds that do not contain elemental elements but have metal conductivity. At present, there are more researches on polyacetylene, perovskite oxide, tungsten bronze and so on. Polyacetylene has good flexibility and flexibility, and can be used as a large-area electrode material for high-capacity plastic batteries. The transition metal-rare-earth perovskite oxide can be used as an oxygen electrode of a fuel cell or as a conversion catalyst for automobile exhaust treatment. The resistance value of LaNiO ₃ changes when it contacts ethanol, and it can be used as an ethanol sensor. Tungsten bronze is a type of M _x WO ₃ type compound, in which M is hydrogen, alkali metal, silver, etc., which can be used as an electrochromic display, and can also be used as the anode material of a battery.

Recently, many such compounds have been developed successively: they are completely free of metal elements but do have metal conductivity. Some compounds are molecular crystals of organic compounds composed of carbon, hydrogen, nitrogen, sulfur, etc., they are called organic metals or molecular metals; some compounds are inorganic polymer compound crystals composed of only nitrogen and sulfur. In addition, there is another kind of organic or organic compounds containing mercury, platinum, nickel, etc.

These synthetic metals also have one thing in common, which is that they are all low-dimensional materials. Although it is called a low-dimensional material, it is actually a substance that occupies a three-dimensional space from the appearance. Therefore, from a strict definition, low-dimensional materials do not exist. These materials are called quasi-one-dimensional or low-dimensional materials, and only after being synthesized have they been measured to find new phenomena not found in three-dimensional materials.

These phenomena have been predicted theoretically. The theory can be compared with experiments, and new phenomena with close relations between them are being proved. And it was found that the conductivity of most quasi-one-dimensional compounds, like metal, increases with decreasing temperature, but at a certain temperature, the conductivity drops sharply and becomes an insulator. Today, this phenomenon is called Peierls transfer, but in 1955 when it was completely unknown about one-dimensional compounds, etc., in the solid physics textbook by Peiers, This phenomenon is discussed as the same one-dimensional lattice deformation problem.

The unique phenomenon of one-dimensional compounds is to cause Peiers transfer. As a result, long-term fluctuations in which charge density and lattice deformation are combined into one are generated. This undulation is called

Recently, due to the popularity of research on synthetic metals, a large number of synthetic metals with various characteristics are found every year, so the classification of synthetic metals is not static. For convenience, Anxi et al. Divided them into six categories: (1) organic metals; (2) polymer complexes; (3) inorganic polymers; (4) platinum complexes; (5) mercury complexes; (6) Interlayer compounds. (1) and (2) are introduced below.

(1) Organic metal

(1) Structure

Organic metal, generally taken

For synthetic metals, not only it is expected to have excellent characteristics, but also from economic considerations, low manufacturing costs and rich resources are required. Most metal elements are scarce. Even if they are rich in resources, it takes a high cost to produce pure metals. Materials such as polyacetylene are polymers composed of a large amount of carbon and water (and several dopants) that exist on the earth and are easy to use. Their properties are the same as those of metals and semiconductors. This material is of great significance for the depletion of metal resources in the future. Therefore, it is also very suitable to call it a synthetic metal. On the other hand, there is another type of metal compound, such as tungsten bronze, which has the properties of general metals and functions that metal does not have (such as ion diffusion function), and its application value cannot be ignored. This type of metal compound is a group of materials that can be called synthetic metals.

Since the research history of synthetic metals is not relatively long, we should have a continuous understanding and deepening process of industrial application of synthetic metals. With the advancement of science and technology, we will have a deeper understanding of the nature of charge carriers flowing in synthetic metals, which will promote our understanding of the role of highly conductive porphyrins in biological systems. TCNQ's good electron-accepting ability has been designed to study the transition of polarized heads in certain phospholipids, determine and characterize the performance of metal oxides as catalysts, and to determine the critical micelles of surfactant Concentration and so on. If the superconducting temperature of synthetic metals can reach temperatures higher than the current inorganic compounds, their industrial application prospects will be very broad, and they will be used to make efficient electric motors and very powerful electromagnetic components. , The functional elements of a supercomputer with very little heat output, and so on. All in all, synthetic metals have a bright future. ^{[3] [3]}