According to a report by the American Physicist Network on November 9 (Beijing time), in 2003, scientists built a new type of carbon structure in the experiment, but this discovery has been controversial; recently, two different studies The team used a different method to identify a three-dimensional network structure called the body-centered tetragonal carbon, which is considered to be the same as that found in 2003.
Pure carbon exists in a variety of different structural forms, such as graphite and diamond. The structure of this new body-centered tetragonal carbon is unexpectedly simple. Between the carbon atomic cube of diamond and the hexagonal lattice of carbon atoms of graphite, it is a square piece containing 4 carbon atoms, perpendicular to the square piece. Short keys are connected. This form of carbon is formed by high pressure of graphite at normal temperature.
It is well known that graphite is reversible in a cold-pressed environment (high pressure is applied at room temperature). In 2003, researchers at Stanford University in the United States compressed graphite in a diamond anvil and acquired an X-ray diffraction pattern to help determine the bonds within the structure. They found that when the pressure exceeds 17 gigapascals (170,000 atmospheres), the carbon atoms in the normally soft graphite form a material that is hard enough to pulverize the diamond, but its structure is not known.
In the latest issue of Physics Review B, a team of scientists led by Wang Huitian of Nankai University in China showed through computer simulation that this superhard carbon is at least partly composed of body-centered tetragonal carbon. The team studied 15 possible structures and found that transparent body-centered tetragonal carbon can be formed with very little energy, and its shear strength is even 17% higher than that of diamond. If this conclusion can be confirmed, it means that it can produce a stronger material than diamond at room temperature.
In the March issue of Physical Review Letters, another group of scientific research teams, including Renat Wentzkevi of the University of Minnesota and Miyake Takashi of the Japan Industrial Technology Research Institute, used different methods. A similar conclusion came out. Using quantum mechanical simulations to analyze the body-centered tetragonal carbon structure, the team found that body-centered tetragonal carbon is more stable than graphite at 18.6 gigapascals, and M-carbon (a structure containing a ring layer of five and seven carbon atoms) After mixing, the X-ray diffraction pattern produced by it is highly compatible with the carbon structure found in 2003.
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