Liquid boron: X-ray measurements and ab initio molecular dynamics simulations
Résumé
We report results of a comprehensive study of liquid boron with x-ray measurements of the atomic structure and dynamics coupled with ab initio molecular dynamics simulations. There is no evidence of survival into the liquid of the icosahedral arrangements that characterize the crystal structures of boron but many atoms appear to adopt a geometry corresponding to the pentagonal pyramids of the crystalline phases. Despite similarities in the melting behavior of boron and silicon, there is little evidence of a significant structural shift with temperature that might suggest an eventual liquid-liquid phase transition. Relatively poor agreement with the observed damping of the sound excitations is obtained with the simple form of mode-coupling theory that has proved successful with other monatomic liquids, indicating that higher-order correlation functions arising from directional bonding and short-lived local structures are playing a crucial role. The large ratio of the high frequency to the isothermal sound velocity indicates a much stronger viscoelastic stiffening than in other monatomic liquids.
Mots clés
ab initio calculations
bonds (chemical)
boron
damping
elemental
semiconductors
high-frequency effects
liquid semiconductors
liquid
structure
liquid-liquid transformations
melting
molecular dynamics
method
silicon
viscoelasticity
total-energy calculations
wave basis-set
supercooled liquid
phase-transition
aluminum-oxide
density
spectroscopy
germanium.
germanium