## 3 Results
### Statistical Geometry Method  
The VP distributions calculated at a temperature of 950 K for individual ionic subsystems by the number of faces (\(n\) distribution) are shown in Figure 10. Each of the subsystems has its own distinct form of the others' \(n\) distribution. The most extended is the \(n\) distribution for the F ion subsystem. The maximum of this distribution is not clearly expressed and falls on \(n_{m}=7\). This form of this distribution is due to the high mobility of F ions and their abundance. The subsystem of sodium ions, inferior to all in number, is characterized by the narrowest \(n\) distribution. The maxima of the \(n\) distributions for subsystems Na and K fall on \(n_{m}=4\), and for the Li ion subsystem \(n_{m}=7\).  
The distributions of VP faces by the number of sides (m distributions) are characterized by a wider representation of \(m\)-edge faces for the faster ion subsystems (F and Li) (Figure 11). Moreover, in these cases, the maximum m of the distribution falls on \(m_{m}=5\). For subsystems with slow diffusion and a small number of ions (K and Na), the locations of the maxima change to \(m_{m}=4\) for K\({}^{+}\) and to \(m_{m}=3\) for Na\({}^{+}\). The \(n\) and \(m\) distributions with \(n=4\) and \(m=3\) are seen in about 65% of the cases for the Na subsystem. This is an indication that for the sodium ion subsystem, in most cases, tetrahedral mutual arrangement of ions is observed.  
In four subsystems of different ions (Li, Na, K, F), the angular distribution of the nearest geometric neighbors (\(\theta\) distribution) characteristic only for them (Figure 12) is found. The angular distribution for the lithium ion subsystem has two weakly resolved peaks of approximately the same intensity. In the case of subsystems of Na and K ions, the first peak has a high intensity, and the second peak has a low intensity and resolution. The difference between them is that in the first case, the global maximum of the spectrum falls at the angle \(\theta=45^{\circ}\), and in the second case, at \(\theta=60^{\circ}\). In addition, the \(\theta\) spectrum for the Na subsystem is significantly jagged due to the small number of Na ions in the model. For the F ion subsystem, two peaks of the main part of the \(\theta\) spectrum have an extremely poor resolution. Moreover, the intensity of the second peak is slightly higher than the intensity of the first peak. An important feature of this distribution is the appearance of a peak in the  
Figure 10: The distribution of Voronoi polyhedra by the number of faces for the Li, Na, K and F subsystem of molten salt mixture FLiNaK+CeF\({}_{3}\) at a temperature of 950 K.  
vicinity of the angle \(\theta=0^{\circ}\), which was not observed in any of the \(\theta\) spectra obtained for systems of positive ions.  
The behavior of Ce ions in the molten salt mixture FlLiNaK-CeF\({}_{3}\) is characterized by the distributions shown in Figure 13. As can be seen from the figure, 88.5% of all polyhedra characterizing the subsystem of Ce ions are 4-faced polyhedra. At the same time, it can be seen from the m distribution (inset) that the number of triangular faces in VPs is 92%. Therefore, with a high degree of probability, the packing of Ce ions in the considered subsystem is tetrahedral. The angular distribution of the nearest geometric neighbors  
Figure 11: The distribution of faces of Voronoi polyhedra by the number of sides for the Li, Na, K and F subsystem of molten salt mixture FlLiNaK+CeF\({}_{3}\) at a temperature of 950 K.  
Figure 12: Angular distributions of nearest geometric neighbors for the Li, Na, K and F subsystem of molten salt mixture FlLiNaK+CeF\({}_{3}\) at a temperature of 950 K.  
for this subsystem has two well-resolved peaks with maxima localized at \(\theta_{m}=60^{\circ}\) and \(105^{\circ}\), respectively.