Abstract
The static and dynamic properties of liquid Zn have been studied using an ab initio molecular dynamics method. Results are reported for the thermodynamic states at 723K near which inelastic neutron and x-ray scattering data are available. The calculated static structure shows very good agreement with experimental measurements, including an asymmetric main peak. The dynamic structure reveals the existence of propagating density fluctuations, and the associated dispersion relation has also been calculated. The possible coupling between longitudinal and transverse excitation modes has been investigated by looking at specific signatures in two wavevector regions: the first one is located around the position of the main peak of the structure factor, qp , as suggested by the recently reported appearance of high frequency transverse waves in several liquid metals under high pressures; the second region is around qp /2, as suggested by inelastic scattering experiments for liquid Zn and other metals.
Highlights
In the periodic table, zinc is at the end of the transition metals series, presenting a full d shell that contributes in an essential way to its properties
£e-mail: beatriz@metodos.fam.cie.uva.es concerning its dynamic properties, recent measurements performed using either inelastic x-ray scattering (IXS) at 713 K or inelastic neutron scattering (INS) at 773 K, have concluded that the data is compatible with the existence of two types of propagating excitations in the density uctuations for wavevectors around qp=2, where qp denotes the position of the main peak of S(q) [4, 5]
The scattered intensity obtained in an IXS experiment is directly related to S(q; !), a proper comparison between the ab initio molecular dynamics (AIMD) result and IXS data requires taking into account the dierence between the simulations, where atoms are classical particles, and the photon scattering which is a quantum process
Summary
Zinc is at the end of the transition metals series, presenting a full d shell that contributes in an essential way to its properties. When coming to the solid, the ground state is a hexagonal close packed structure, but the ratio between the c and a axis is extremely large, 1:856, around 15 % higher than the ideal value corresponding to hard spheres Concerning its dynamic properties, recent measurements performed using either inelastic x-ray scattering (IXS) at 713 K or inelastic neutron scattering (INS) at 773 K, have concluded that the data is compatible with the existence of two types of propagating excitations in the density uctuations for wavevectors around qp=2, where qp denotes the position of the main peak of S(q) [4, 5] These complexities pose the requirement of a highly accurate description of the interactions present in the system in order to carry out a theoretical study of the properties of liquid Zn (l-Zn). The electron-ion potential has been modeled through an ultrasoft pseudopotential that considers 12 valence electrons, as incorporated in the dataset included in the VASP utility
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