# Molecular Dynamics Simulation of Bulk Cu Material under Various Factors
## 3 Results and Discussion
### Influencing Factors
#### 3.2.3 Effect of Annealing Time  
The obtained results show that when annealing the bulk Cu\({}_{5324}\) material at the glass temperature T\({}_{\text{g}}\) = 652 K, at t1 = 0 ps, E\({}_{\text{tot}}\) = \(-\)17791 eV. When the annealing time was increased from t1 = 0 ps to t2 = 40 ps, t3 = 100 ps, t4 = 150 ps, and t5 = 200 ps, E\({}_{\text{tot}}\) decreased from E\({}_{\text{tot}}\) = \(-\)17791 eV to E\({}_{\text{tot}}\) = \(-\)17821, \(-\)17832, \(-\)17837, and \(-\)17848 eV, which proves that when annealing at the temperature point T\({}_{\text{g}}\) in glass, E\({}_{\text{tot}}\) decreases very quickly (Figure 5). This obtained result is completely consistent with the simulation results of previously studied metals Al [63], Fe [64], and Ag [65]. Through the obtained results, it was shown that when metal was annealed at glass temperature T\({}_{\text{g}}\), metallic materials always tend to increase crystallization. There is a problem: in the course of experimental research, there is always the question of which point is the most standard glass temperature of a metal. To confirm the accuracy of the obtained results, we continue to study the effect of the annealing time at glass temperatures above T\({}_{\text{g}}\), and the results are shown in Figure 6.  
The obtained results showed that the material of bulk Cu\({}_{5324}\) at T\({}_{\text{g}}\) = 652 K and annealing time (t) t1 = 0 ps had a structure shape (Figure 6(a1)); the number of structural units was shown by 168 FCC, 1954 HCP, 744 BCC, and 2458 Amor (Figure 6(a2)); and length of the links r\({}_{\text{Cu-Cu}}\) = 2.475 A, g(r) = 4.31, 1 = 3.25 nm, and E\({}_{\text{tot}}\) = \(-\)9931 eV (Figure 6(a3)). When the annealing time increased from t1 = 0 ps to t2 = 40 ps, t3 = 100 ps, t4 = 150 ps, and t5 = 200 ps, the structural shape of the material changed (Figure 6(a1,b1,c1,d1,e1)) with the FCC increasing from 168 FCC to 769 FCC. In addition, the HCP increased from 1954 HCP to 1769 HCP, the BCC increased from 744 BCC to 878 BCC, and the Amor increases from 2458 Amor to 1908 Amor (Figure 6(a2,b2,c2,d2,e2)). Corresponding, r increased from r\({}_{\text{Cu-Cu}}\) = 2.473 A to r\({}_{\text{Cu-Cu}}\) = 2.473, 2.474, 2.474, r\({}_{\text{Cu-Cu}}\) = 2.475 A, g(r) changed from about g(r) = 4.31 to g(r) = 4.12, l decreased slightly from l = 3.973 nm to l = 3.971 nm, and E\({}_{\text{tot}}\) decreased from E\({}_{\text{tot}}\) = \(-\)9931 eV to E\({}_{\text{tot}}\) = \(-\)23525 eV (Figure 6(a3,b3,c3,d3,e3)). The obtained results show that when increasing the annealing time, the length of the link of Cu-Cu increased from r\({}_{\text{Cu-Cu}}\) = 2.473 A to r\({}_{\text{Cu-Cu}}\) = 2.475 A, consistent with the results obtained earlier for metal [42; 43; 62] and alloy [44; 45; 46; 47]. The obtained results showed that after the annealing time at the glass temperature, the crystallization process increased. Figure 5: The crystalline phase transition of bulk Cu\({}_{5324}\) material at glass temperature T\({}_{\text{g}}\) = 652 K after annealing time t = 200 ps. Figure 6: Structural characteristic quantities, such as: structure shape (**a1,b1,c1,d1,e1**), number of structural units (**a2,b2,c2,d2,e2**), and radial distribution function (**a3,b3,c3,d3,e3**) of bulk Cu\({}_{324}\) material with different annealing times. As has been emphasized in [38, 85], several kinds of crystalline structures, HCP, BCC, and FCC, can exist in simulations of different quenching processes (for different heating rates) and even of used potentials. It is well-known that in the imperfect crystallization of Cu, the FCC structure should be dominated, but in [85], the authors used the bond pair analysis technique to show that icosahedral, BCC, and tetrahedral SRO were dominant in the glass state for the quenching rate, with an average cooling rate of 2 \(\times\) 10\({}^{14}\) K/s, and that during the rapid quenching process of Cu, there may exist an intermediate BCC phase between the fully amorphous phase and the FCC phase.