Variational calculation of Helmholtz free energies with applications to the sp-type liquid metals

Structural evolutions and hereditary characteristics of icosahedral nano-clusters formed in Mg70Zn30 alloys during rapid solidification processes

To investigate the structural evolution and hereditary mechanism of icosahedral nano-clusters formed during rapid solidification, a molecular dynamics (MD) simulation study has been performed for a system consisting of 10⁷ atoms of liquid Mg₇₀Zn₃₀ alloy. Adopting Honeycutt-Anderson (HA) bond-type index method and cluster type index method (CTIM-3) to analyse the microstructures in the system it is found that for all the nano-clusters including 2~8 icosahedral clusters in the system, there are 62 kinds of geometrical structures, and those can be classified, by the configurations of the central atoms of basic clusters they contained, into four types: chain-like, triangle-tailed, quadrilateral-tailed and pyramidal-tailed. The evolution of icosahedral nano-clusters can be conducted by perfect heredity and replacement heredity, and the perfect heredity emerges when temperature is slightly less than T_m then increase rapidly and far exceeds the replacement heredity at T_g; while for the replacement heredity, there are three major modes: replaced by triangle (3-atoms), quadrangle (4-atoms) and pentagonal pyramid (6-atoms), rather than by single atom step by step during rapid solidification processes.

Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study

The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90–150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule.

Atomic mechanism of liquid-glass transition for Ca7Mg3 alloy

The atomic mechanism of liquid-glass transition for Ca(7)Mg(3) alloy during the rapid quenching processes is studied by the molecular dynamics simulations. The temperature dependences of structural, thermodynamic, and dynamic properties during the liquid-glass transition have been investigated. It is found that onset temperatures where these different properties begin to deviate from the equilibrium liquid are identical and near the melting temperature T(m). The liquid-glass transition temperatures in structure (T(g)(Str)) and dynamics (T(g)(Dyn)) are identical and higher than the calorimetric one (T(g)(Cal)), which are consistent with many experiments and computer simulations. The solid- and liquid-like atoms are defined by the Debye-Waller factor. It reveals that the solid-like atoms hold lower potential and higher degree of local order. On the basis of the evolution of solid-like atoms, the atomic mechanisms in structure, thermodynamics, and dynamics transition are systematically elucidated, which are consistent with the potential energy landscape.