Atoms constituting a metal define its molecular crystal structure (atomic system) and interact in molecular dynamics simulations of nanometric cutting of the metal. The removal of the material (metal) at nanoscale and generation of high quality surface with a nanometric finish is largely influenced by the mechanical and physical properties of the metal as it associates with the metal lattice (atomistic) structure. Improved studies of the molecular modelling (behaviour of molecules) as it creates mathematical models of molecular properties and behaviour of atomistic systems are required for condition prediction of a nanometric surface finish. In this study, atomic system of rapidly solidified aluminium (RSA) alloy, grade RSA 431, with the use of its alloying elemental compositions by weight percentage is designed and constructed with cell geometry and atom positions that are written into a data file using AtomsK program. In addition, atomic concentration influencing the structural properties of the alloying elements were calculated. Obtained microstructure depicts the spread of the elemental compositions and the data file is suitable for a code performing simulations on classical particles like the large-scale atomic/molecular massively parallel simulator (LAMMPS) software. Understanding the computer simulations (molecular dynamics) for analyzing the physical movements of atoms and molecules, and the peculiar characteristic properties of the composing alloying elements of the RSA 431 determine how much influence each of them (elements) has on the nanometric cutting surface. Hence, the nanometric surface finish of the RSA 431.