# Molecular Dynamics Simulation of Bulk Cu Material under Various Factors
## 3 Results and Discussion
### Influencing Factors
#### 3.2.2 Effect of Temperature  
The effect of temperature on the structural characteristics and phase transition of bulk Cu\({}_{5324}\) material are shown in Table 2.  
The obtained results show that when T increased from T = 300 K to T = 1000 K, the E\({}_{\rm tot}\) decreased from E\({}_{\rm tot}\) = \(-\)18125 eV to E\({}_{\rm tot}\) = \(-\)17491 eV, the size I increased trivially from I = 3.970 nm to I = 3.974 nm, r decreased from r\({}_{\rm Cu-Cu}\) = 2.475 A to r\({}_{\rm Cu-Cu}\) = 2.472 A, and the \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**T (K)** & 300 & 400 & 500 & 600 & 700 & 800 & 900 & 1000 \\ \hline
**r (Å)** & 2.475 & 2.475 & 2.474 & 2.474 & 2.473 & 2.473 & 2.472 & 2.472 \\ \hline
**g(r)** & 4.87 & 4.65 & 4.40 & 4.33 & 4.22 & 4.05 & 3.86 & 3.60 \\ \hline
**FCC** & 297 & 328 & 330 & 285 & 244 & 254 & 219 & 163 \\ \hline
**HCP** & 2190 & 2139 & 2123 & 2117 & 2116 & 1941 & 1820 & 1779 \\ \hline
**BCC** & 675 & 702 & 753 & 772 & 762 & 789 & 771 & 794 \\ \hline
**Amor** & 2162 & 2155 & 2115 & 2150 & 2202 & 2340 & 2514 & 2558 \\ \hline
**l (nm)** & 3.970 & 3.970 & 3.972 & 3.972 & 3.973 & 3.973 & 3.974 & 3.974 \\ \hline
**E\({}_{\rm tot}\)** & \(-\)18125 & \(-\)18053 & \(-\)17979 & \(-\)17895 & \(-\)17808 & \(-\)17709 & \(-\)17605 & \(-\)17491 \\ \hline \end{tabular}
\end{table} 
Table 2: The structural characteristics and phase transition of bulk Cu\({}_{5324}\) material are shown in Table 2.  
Figure 3: Relationship between number of atoms and size (**a**) and between number of atoms and total energy of the system (**b**) when changing the atom number. g(r) decreased from g(r) = 4.87 to g(r) = 3.60. Correspondingly, with the number of structural units FCC, HCP decreased from 297 FCC to 163 FCC and 2190 HCP to 1779 HCP, BCC increased from 675 BCC to 794 BCC, and Amor increased from 2162 Amor to 2558 Amor (Table 2). The obtained results show that with an increase in the temperature, the length of the link of Cu-Cu decreased and was consistent with the results obtained earlier for metal [42; 43; 62] and alloy [44; 45; 46; 47]. The relationship between the E\({}_{\text{tot}}\) and T is shown in Figure 4.  
The obtained results show that with increases in the temperature T, E\({}_{\text{tot}}\) always increased in linearity and was proportionally linear with T from about T = 300 K to T = 600 K and from T = 700 K to T = 1000 K. Increasing T led to l negligibly increasing; E\({}_{\text{tot}}\) increasing; the number of structural units FCC, HCP, and BCC decreasing; and Amor increasing, which indicates that approximately T = 600 K to T = 700 K is the glass temperature of bulk Cu\({}_{5324}\) material. According to the graph results, the intersection point between the two temperature ranges is called the glass point or the glass temperature (T\({}_{\text{g}}\)), with the value T\({}_{\text{g}}\) = 652 K (Figure 4); the causes of this phenomenon are the size effect and the surface effect, and the phase transition of bulk Cu\({}_{5324}\) materials is a phase transition of type 1. To determine the crystallization process of bulk Cu\({}_{5324}\) material at the glass transition temperature T\({}_{\text{g}}\) = 652 K, we investigated the effect of annealing time; the content will be presented in detail in the following section. [PERSON] et al. [85] first made a proper choice of the metal Cu as the subject of their research for analyzing the structural change from the liquid to the solid state. Instead of using the Suto-Chen (SC) potential as the present work did, they performed an ab initio MD simulation that described the transition procedure to Cu glass and some structural features of metallic glasses. Although the number of Cu atoms was not large (150), the authors conducted a very interesting analysis that is similar to our consideration related to Figure 4. On the basis of the energy dependence of time (Figure 2 in [85]), they noticed the difference in simple deviations around the transition temperature to the glass.