# Structure of Argon Solid Phases Formed from the Liquid State at Different Isobaric Cooling Rates
## 1 Introduction  
The molecular structure of solids makes a significant contribution to the manifestation of certain anisotropic rheological, optical, and even electrical and magnetic properties in them. For example, in the development of integrated circuits, the priority is to obtain single crystals of silicon of macroscopic dimensions, but an even more promising task may be the synthesis of a crystal with a uniform spatial distribution of Schottky defects, which would allow the valence impurities to be fully replaced and the purest semiconductor material to be obtained. The selection of conditions for the synthesis of materials with a given structure, as well as the development of methods for quantifying the structure of solids, are priority tasks of materials science and nanotechnology.  
Full-scale research methods, such as X-ray diffraction, allow us to quantify the structure only in a small surface layer of the sample under study, currently tomographic methods for studying bulk crystal structures are still at the level of the concept. In this regard, numerical experiments by the method of molecular dynamics are a kind of \"panacea\" in the problems of determining quantitative structural characteristics, because in the process of modeling, the researcher has full access to the array of coordinates of the particles ofthe system, which allows operating this array, subjecting it to processing by clustering algorithms and structure recognition [1; 2; 3].  
Methods of molecular dynamics allow performing computer experiments in which it is possible to simulate thermodynamic processes of molecular systems undergoing phase transitions. This approach can be useful for the selection of conditions for the thermal and baric synthesis of new materials.  
Modeling of thermodynamic processes in particle systems with complex chemical bonds is accompanied with great algorithmic and computational difficulties. Therefore, it remains relevant to conduct computer experiments on simple models such as monoatomic particle systems with spherically symmetric interaction potentials in order to develop and test new methods and algorithms and the prospect of their further transfer to more complex models [4; 5; 6; 7; 8; 9; 10].  
In this paper, we propose methods for quantitative analysis of coordinate arrays of particles for the presence of elementary cells of a face-centered cubic structure in them, which were tested on the results of numerical experiments on cooling argon from liquid to solid under various conditions. Of course, the above model experiments are quite difficult to repeat _in situ_, but the calculations performed correspond to the physical nature of the crystallization and glass transition processes and predict the behavior of argon under conditions of intense thermodynamic processes.  
The performed studies on the argon model allow us to assert that when choosing the values of the applied pressure and the cooling rate, materials with different structures can be obtained from the liquid phase: single crystals, single crystals with lattice defects, polycrystals, composite substances representing clusters and crystal cells distributed in a glassy mass, as well as glassy media devoid of crystal nuclei.