Molecular Dynamics Study of Stability of Solid Solutions and Amorphous Phase in the Cu–Al System

Abstract

The relative stability of 𝑓 𝑐𝑐 and 𝑏𝑐𝑐 solid solutions and amorphous phase with different compositions in the Cu-Al system is studied by molecular dynamics simulations with 𝑛-body potentials. For Cu1−𝑥Al𝑥 alloys, the calculations show that the 𝑓 𝑐𝑐 solid solution has the lowest energies in the composition region with 𝑥 < 0.32 or 𝑥 > 0.72, while the 𝑏𝑐𝑐 solid solution has the lowest energies in the central composition range, in agreement with the ball-milling experiments that a single 𝑏𝑐𝑐 solid solution with 0.30 < 𝑥 < 0.70 is obtained. The evolution of structures in solid solutions and amorphous phase is studied by the coordination number (CN) and bond-length analysis so as to unveil the underlying physics. It is found that the energy sequence among three phases is determined by the competition in energy change originating from the bond length and CNs (or the number of bonds).

Reconstruction of magnetohydrodynamic equilibrium configurations with hollow current density profiles in the HL-2A tokamak

“…The configurations have mainly been created with neutral beam injection and radio-frequency current drive in recent decades. For example, lower-hybrid current drive (LHCD) experiments were performed and a slightly hollow current profile was realized in the HL-1M tokamak [7,8]. The studies also show that magnetohydrodynamic (MHD) instabilities are successfully suppressed in LHCD experiments [8,9].…”