# Molecular Dynamics Study on the Crystallization Process of Cubic Cu-Au Alloy
## 1 Introduction
There are many methods to research and fabricate Cu-Au alloys, such as theoretical methods, experimental methods, and simulation methods. In particular, experimental methods, including chemical methods, have determined that Cu-Au alloys depend not only on the size but also depend on the ratio between gold and copper. The X-ray method has determined the X-ray diffraction spectral structure and the energy of valence electrons of Cu\({}_{3}\)Au and Cu-Au\({}_{3}\) alloys in the ordered and unordered states [18]. Simulation methods include: the colloidal model [19], the Finnis-Sinclair model (FS) [20], the Embedded Atom Method (EAM) [21], and the Sutton-Chen (SC) model [22] potential and Slag Models Approximation (SMA) (with the Tightly Bound (TB) model [23]). The simulation method was considered a semi-empirical method and was applied in studies of structural properties of metals and alloys [24; 25; 26; 23] through the atomic force field [27; 28; 29; 30], as well as in studies of structural phase transitions in metals and alloys, based on the potential field parameters from the components of the pure atom [27; 28; 29; 30; 31]. For specific applications, it is necessary to perform some approximations to determine the properties of materials, such as link length, lattice constant, energy, and phase transition temperature [32]. Additionally, theoretical models, based on quantum calculations, are applied to determine the parameters of the simulation model, in different studies about the structural properties, phase transitions, and crystallization of alloys [33]. Many researchers have successfully used the potential field of Rafii-Tabar and Sutton-Chen (SC) [21] to study the binary Face-Centered Cubic (FCC) structure for the alloy without changing the original elemental parameters [21; 34]. The SC potential belongs to the class of optimized Embedded Atom Method (EAM), where the energy of the considered system is calculated by embedding a given atom in the local density field of electrons created by the other atoms surrounding it. The parameters of SC potential are fixed by fitting first principles and experimental data for Cu, Au, and Cu-Au binary compounds, such as the lattice parameter, cohesive energy, bulk modulus, elastic constants, and phonon dispersion curves, tested for accurate values of surface energies, etc. The simple power law of the SC potential gives us a faster numerical algorithm than in the case of general EAM. Furthermore, scientists [35] reconstructed the Sutton-Chen (SC) potential by adding quantities, such as phonon frequency and zero energy, and called this new interaction the potential Quantum Sutton-Chen (Q-SC) [36; 37; 38; 39; 40]. Cu-Au alloys are also applied in lower CO oxidation than pure metals [41]. It is known that the catalytic activities of the materials determined through the surface effect strongly depend on the structural properties [42; 43; 44]. In some studies, the energies of Cu, Au, and Cu-Au metals, were determined by the EAMforce field [45] with Cu\({}_{3}\)Au [46]. However, the crystallization of Cu-Au alloy occurs more easily than that of Cu\({}_{3}\)Au [47]. Based on these studies, it can be specified that there is a major influence of the structure on the mechanical properties of Cu-Au [48] and the properties of Cu-Au [49; 50]. In addition, the effect of anisotropy on the deformation process has been found to have a nonlinear symmetry at low temperatures [51]. Morse interaction potential is widely used in the process of studying defects and deformation of metals and alloys [52; 53]. Several studies revealed the Cu-Au alloy is a binary alloy that survives temperature-induced transformation and is stable long term, with a super-cohesive structure [54; 55; 56; 57; 58]. In addition, the phase transition of Cu-Au alloy follows the type I phase transition such as T \(>\) 683 K, having face-centered cubic (FCC) structure, T \(<\) 543 K exist a tetragonal structure, and for 543 K \(<\) T \(<\) 683 K there is a phase transition temperature range [59].