Читать книгу Amorphous Nanomaterials - Lin Guo - Страница 16

The concept of amorphous is defined in the comparison of crystallography in solid physics. Therefore, the history of amorphous materials should be compared with that of crystallography.

On 25 June 2012, the General Assembly of the United Nations adopted a resolution, which proclaiming the year 2014 as the International Year of Crystallography. It was named to commemorate Max von Laue, who won the Nobel Prize in Physics of 1917, about 100 years ago for characterizing the crystal structure by X-ray. At the same time, it was also commemorated Johannes Kepler proposed the famous article A New Year’s Gift of Hexagonal Snow 400 years ago (1611). He was regarded as the first one to conceptualize the symmetry of crystals which were formed by a regular accumulation of spherical elements. It was considered to be the beginning of the establishment of traditional crystallography.

In 1699, Nicolas Steno observed a large number of ores and proposed that the angle between two identical crystal planes of a crystal is always constant, regardless of the size and shape of the crystal plane [9]. It was called the law of constant angles of the crystal plane, which was generally recognized as the first law of crystals. Prior to the discovery of X-ray, the law laid the foundation for crystal identification, and the word Crystal began to be used to describe substances with regular morphologies and fixed angles.

In 1784, Rene Just Hayuy proposed that each crystal plane was simply composed of blocks of the same size and shape. The crystal structure was described as a regular three-dimensional arrangement, which was an infinite repetition of cells in the three-dimensional directions. On this basis, William Hallowes Miller proposed in 1839 that each crystal plane can be described by three simple integers (h, l, k). That was the Miller Index, as was still used today.

At the end of the nineteenth century, from a mathematical point of view, scientists put forward 32-point groups to describe the symmetry of crystal shape and 230 space groups to nominate the symmetry of microelements. Until now, all the geometric structure characteristics of crystallography have been basically perfected.

In 1912, on the basis of Laue’s work, William Lawrence Bragg proposed the famous Bragg Formula, which laid the foundation for the establishment of modern crystallography and the characterization of crystal structure. Later, together with his father William Henry Bragg, he quickly characterized the crystal structure of various substances, and established modern crystallography soon [10].

From the development history of crystallography, we can find that the confirmation of crystal structure characteristics depends on the discovery of X-ray, but the establishment of geometric theory in crystallography was far before the characterization of its crystal structure. All the elements in the definition of crystals (crystals are solids with regular periodic repetitive arrangement of internal particles in three-dimensional space) are determined before X-ray discovery. The establishment of crystallography depends more on the mathematics-induced theoretical system and physics-drove technique.