Abstract
The atomic dynamics of Al2O3 melt are studied by molecular dynamics simulation. The particle interactions are described by an advanced ionic interaction model that includes polarization effects and ionic shape deformations. The model has been shown to reproduce accurately the static structure factors S(Q) from neutron and x-ray diffraction and the dynamic structure factor S(Q,!) from inelastic x-ray scattering. Analysis of the partial dynamic structure factors shows inelastic features in the spectra up to momentum transfers, Q, close to the principal peaks of partial static structure factors. The broadening of the Brillouin line widths is discussed in terms of a frequency dependent viscosity �(!).
Highlights
In recent years, substantial progress has been achieved in understanding the atomic dynamics of liquids
This is mainly due to two achievements, i.e., the development of inelastic x-ray scattering (IXS) as complementary technique to inelastic neutron scattering (INS) and the increasing power of computer simulations
This analysis suggests that in Al2O3 at 2500 K the damping of the high-Q acoustic modes observed in IXS is crossing over from the hydrodynamic, viscous damping associated with structural relaxation of the fluid, to damping associated with the vibrational dynamics of the atoms about some disordered configuration in which the atoms are trapped on the timescale of the acoustic oscillations
Summary
Substantial progress has been achieved in understanding the atomic dynamics of liquids This is mainly due to two achievements, i.e., the development of inelastic x-ray scattering (IXS) as complementary technique to inelastic neutron scattering (INS) and the increasing power of computer simulations. Rigid ion models of Born-Mayer-type, for example, subsume the many-body effects in some average sense and may be capable of reproducing some of the experimental results They often do not provide a reliable description of both static and dynamic properties. An advanced ionic model of AIM-type [21] was recently used to perfectly reproduce both the experimental static and dynamic structure factors of alumina melt [22]. We focus on the relations between the spectra of collective modes, the vibrational spectra and the structural relaxation processes in the melt
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