# Structure of Argon Solid Phases Formed from the Liquid State at Different Isobaric Cooling Rates
## 3 Results  
Figure 3 shows the results of calculating the concentration of FCC cells in argon solid phases at a temperature of 40 K, obtained as a result of isobaric cooling with different rates dT/dt at different pressure values.  
It has been established that no crystal structure cells are formed in solid argon during isobaric cooling at speeds of 10\({}^{12}\) K/s and higher. At pressure values of 0.5 MPa and 1 MPa, no FCC structure cells were found in systems formed by cooling at a rate of 10\({}^{11}\) K/s, but at high pressure values, a small concentration of crystal structure cells is observed from 2.3% at a pressure of 2 MPa to 5.5% at a pressure of 4 MPa.  
In molecular systems formed at a cooling rate of 10\({}^{10}\) K/s, the content of crystal structures is estimated at 7-8% at all pressure values maintained during numerical experiments. In systems obtained by cooling at a speed of 10\({}^{9}\) K/s, the content of 15% to 18% of particles located in the nodes of FCC structures was observed, while the correlation between the concentration of the formed crystal structures and the applied pressure ceases to be traced.  
As a result of cooling at a rate of 10\({}^{8}\) K/s, solid argon with a high degree of crystallization is obtained, the results of numerical calculations show the concentration of FCC cells from 27% to 41%, while there is also no correlation with pressure. It is worth noting that when one particle is shifted to a critical distance from the dislocation position in the node, the Wigner-Seitz cells of the neighboring 12 particles are distorted and cease to meet the selection criteria, therefore, the concentration values of the crystal structure cells from 20% should be considered a sufficiently large indicator, in volume ratio clusters of crystal structure in such a system can occupy about 60% spaces.  
The spatial orientation of the Wigner-Seitz cells may reflect the uniformity of the crystal structure and influence the manifestation of anisotropic properties of the solid phase. Of course, the anisotropy of noble gas cryocrystals is rather weakly expressed in comparison with more complex substances, but at the same time, the study of the orientation of the crystal lattice cells at the micro level allows us to trace possible structural defects in ordered media or the unification of individual cells into clusters in less ordered media.  
Figure 4a shows the configuration of argon particles at a temperature of 40 K and a pressure of 3 MPa, obtained as a result of a computer experiment on cooling from the liquid phase at a speed of 10\({}^{8}\) K/s, black lines represent the long diagonals of polyhedra calculated by Voronoi partitioning (particles close to the boundaries of the system were not included in the calculation).  
The orthogonality and parallelism of the axes of symmetry of the Wigner-Seitz cells indicate a high degree of ordering of the particles of the system. The phase shown in Figure 3a is a single crystal with local defects.  
As a result of cooling at a rate of 10\({}^{9}\) K/s at 3 MPa (see Figure 4b), a solid representing a large cluster of crystalline FCC structure immersed in an unordered amorphous medium in which smaller crystal clusters are present.  
At 10\({}^{10}\) K/s cooling (see Figure 4c), the system is an amorphous medium in which differently oriented cells of the crystal structure are evenly distributed, the unification of cells into small clusters of 3-5 elements is noticeable.  
Rapid cooling (10\({}^{11}\) K/s) leads to a more unstructured system (see Figure 4d), in a loosely packed matrix there are rare single cells of the FCC structure whose spatial orientation is chaotic.  
Figure 3: Concentration of FCC cells in solid argon phases formed by isobaric cooling from the liquid phase at speeds of 10\({}^{8}\)–10\({}^{11}\) K/s and at pressure values of 0.5 MPa (**a**), 1 MPa (**b**), 2 MPa (**c**), 3 MPa (**d**), 4 MPa (**e**).