Pressure Effects on the Structural Evolution of Monatomic Metallic Liquid Hafnium
Abstract
Structural evolution of monatomic metallic liquid hafnium under high pressures of 0-50 GPa has been investigated
by molecular dynamics (MD) simulations using the tight-binding (TB) many body potentials during rapidly
solidified processes. The structural evolution and glass formation (GF) process have been analyzed by using pair
distribution functions (PDF), Wendt-Abraham (RWA) parameter, Honeycutt-Andersen (HA) and Voronoi
tessellation (VT) methods. When the system has been cooled with a cooling rate of 2x1013 Ks-1
, the glassy states
are obtained for P≤40 GPa pressures and the crystalline phase is obtained at P=50 GPa pressure. The number of
face-centered cubic (fcc) and hexagonal close-packed (hcp) (fcc + hcp) type bonded pairs increase dramatically,
while the number of perfect icosahedra, distorted icosahedra and body-centered cubic (bcc) type bonded pairs
decreases with increasing of pressure. This is an indication that the solidification process of the system begins with
nucleation in the liquid and that nucleation growth with increasing pressure continues to develop. The results show
that the variation of local atomic bonded pairs is of great importance to understand the glass formation and
crystallization process. However, it has been observed that the applied high pressure (HP) weakened icosahedral
order and increased the fraction of other clusters in glassy hafnium at low temperatures. Furthermore, it has been
observed that all glass transition temperatures (Tg), main bond types and main base clusters change with increasing
pressure.
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