## 3 Results and Discussion  
### Bulk Properties of VFeScZ (Z = Sb, As, P)  
In Figure 2, the type-I structure of VFeScZ alloy is shown dramatically. We can also construct two other structures, which are stipulated as type-II and -III, using the atomic exchange method discussed above. The three types of structures were optimized in the zero-pressure environment, and the recorded results are shown in Table 1. We found that the type-I structure of VFeScZ has the lowest energy among the three types of structures, so it can be judged as the ground state configuration. We also found that the ground state energy difference between the two structures of VFeScAs and VFeScP is 0.03-0.05 eV/primitive-cell, while the ground state energy difference between the two structures of VFeScSb is about 0.5 eV/primitive-cell by contrast. Therefore, the energy of type-II is quite different from that of type-I and -III structures. Based on the above analysis, we can preliminarily judge that the ground state alloys of type-I VFeScAs and VFeScP are not stable enough and may change to type-III structure. So the probability of Fe-Sc atomic disorder occurring in these two alloys is relatively high. But, the type-I VFeScSb has better structural stability, so the atomic exchange disorder rate of Fe-Sc and Fe-V is significantly lower than that of the other two alloys. We present in detail the relationship between the energies and lattice constant changes of VFeScZ (Z = Sb, As, P) system in order to analyze the structural stability of VFeScZ with the three structures in Figure 3. It can be obviously seen that VFeScSb in the ground state has good stability. The energy difference of type-I and -III structure will continue to narrow only when the lattice constant keeps increasing, but, such difference will continue to increase as the lattice constant shrinks. Meanwhile, it was found in both VFeScAs and VFeScP, which is different from VFeScSb, that the energy of type-I and type-III alloys cross with the function diagram of the lattice constant when the lattice constant becomes larger, indicating that VFeScAs and VFeScP alloys are more inclined to form type-III structure with the increase of the lattice constant. But, we can see that the ground state energy difference between type-I, -III, and even -II structures will increase as the lattice constant decreases, which is consistent with the behavior of VFeScSb. In Table 1, the total magnetic moment per primitive cell and the atomic magnetic moment in VFeScZ are also listed. A few results as the following can be deduced, respectively: First, the VFeScSb alloy is focused. In all of the structures, the total magnetic moment is (or is very close to) 3.02 \(\upmu\)B, which is very close to the value of the Slater-Pauling rule, \(M_{\text{t}}=Z_{\text{t}}-18\). The total magnetic moment in primitive cell mainly comes from V for type-I and -II structure, while the magnetism is mainly contributed by the Fe atom for type-III structure. Second, as far as VFeScAs is concerned, the total magnetic moment is 3.00 \(\upmu\)B in a primitive cell and conforms to the Slater-Pauling rule well only in the type-I structures of VFeScAs. For the type-II and -III structures, the total magnetic moments of about 2.80 \(\upmu\)B and 2.18 \(\upmu\)B, respectively, significantly deviated from the Slater-Pauling rule. It is worth noting that in the type-I structure the contribution of V atom to the total magnetic moment is about 2.96 \(\upmu\)B, which is about 98% of the magnetism of VFeScAs. Third, in the VFeScP alloy, it can be