MOLECULAR DYNAMICS STUDY OF STRUCTURE, CRYSTALLIZATION AND PHASE TRANSITION IN BULK CO-MATERIALS: EFFECT OF TEMPERATURE, NUMBER OF ATOMS AND ANNEALING TIME

Abstract

In this work, the structure, crystallization, and phase transition of the bulk Co materials have been characterized via the Molecular Dynamics Simulation (MDS) method combined with the Sutton-Chen (SC) embedded potentials and periodic boundary conditions under various factors such as temperature (T), number of atoms (N), and annealing time (t). The common neighbor analysis revealed the coexistence of Amorphous (Amor) and crystalline Face Centered Cubic (FCC), Body Centered Cubic (BCC), and Hexagonal Close Packed (HCP) phases at an equilibrium state irrespective of the aforementioned factors. Compared with the crystalline FCC and BCC phases, the HCP and Amor phases were found to be dominant in the bulk Co10976 material at T = 300 K. Decreasing N from 10976 to 4000 atoms at T = 300 K and increasing T from 300 to 1000 K in the bulk Co10976 material didn’t change the dominant phases. It was found that the glass transition temperature (Tg) of the bulk Co10976 material was 700 K. Increasing t from 0 to 10 ps at Tg = 700 K abruptly changed the dominant phase of the bulk Co10976 material into the FCC structure. The radial distribution function (RDF) analysis showed that the distance between Co atoms in the bulk Co10976 material was 2.475 Å at T = 300 K. The N and T didn’t affect the distance between Co atoms, but t caused an increase. The size (l) increased from 3.8391 to 5.3320 nm, while the energy (E) decreased from -4.195 to -4.218 eV with increasing N. The first peak height of the RDF (g(r)) first increased and then decreased as the N increased. Increasing T from 300 to 1000 K led to an increment in the E value from -4.218 to -4.087 eV and a slight increase in the l from 5.3320 to 5.3323 nm.