# Molecular Dynamics Simulation of Bulk Cu Material under Various Factors
## 4 Conclusions  
The molecular kinetics method shows that there are factors affecting the structural characteristics of bulk Cu materials, such as the number of atoms, temperature, and annealing time. To determine these characteristics, we used the Sutton-Chen embedded force field to determine the interaction force between atoms, combined with periodic boundary conditions and the Velvet algorithm. At equilibrium, bulk Cu materials always have four types of structural units: FCC, HCP, BCC, and Amor. When increasing the number of atoms (N), leading to an increase in size (I), the total energy of the system (E\({}_{\text{tot}}\)) decreased; while increasing the annealing time (t), I decreased and E\({}_{\text{tot}}\) decreased. As the temperature (T) increased, I increased, and E\({}_{\text{tot}}\) increased. In addition, if t was increased at T = 652 K, the number of FCC, HCP, BCC structural units increased sharply; Amor decreased the most; and the glass transition temperature of bulk Cu material was T\({}_{\text{g}}\) = 652 K. That determines the effect of N, T, and t on the structure and phase transition, crystallization of bulk Cu material. Correspondingly, with Cu-Cu bond lengths increasing in the range of r\({}_{\text{Cu}\text{+Cu}}\) = 2.473 A to r\({}_{\text{Cu}\text{-Cu}}\) = 2.475 A with increasing t and decreasing from r\({}_{\text{Cu}\text{-Cu}}\) = 2.475 A to r\({}_{\text{Cu}\text{-Cu}}\) = 2.472 A with increasing T. The obtained results are completely consistent with previous experimental and simulation results. In addition, as N increased, the I of the material was always proportional to N\({}^{-1/3}\), and the total E\({}_{\text{tot}}\) energy was always proportional to N. However, the obtained results showed that the bulk Cu\({}_{5324}\) material had a glass temperature (T\({}_{\text{g}}\)) = 652 K. When the material was thermally annealed at T\({}_{\text{g}}\) = 652 K after time (t), t = 200 ps had an increase in crystallinity; as the number of structural units FCC, HCP, and BCC increased, Amor decreased, these results are completely consistent with previous studies. Finally, the phase transition and crystallization increase at the glass temperature T\({}_{\text{g}}\) = 652 K of the bulk Cu\({}_{5324}\) material are still unclear and need to be studied further in the future to explain and elucidate why this occurs in the upper and lower temperature ranges of the glass temperature. The obtained results serve as a basis for future research directions of new materials.  
Conceptualization, D.N.T.; methods, D.N.T.; validation, D.N.T.; investigation, D.N.T.; writing--original draft preparation and review, D.N.T., V.C.L. and S.T.; writing--review and editing, D.N.T., V.C.L. and S.T.; data curation, V.C.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The funders had no role in the design of the study; in the collection, analyses, or interpretation of the data; in the writing of the manuscript; or in the decision to publish the results.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data that supports the findings of this study are available from the corresponding author upon reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest.