Abstract
The structure of liquid Bi has been debated in relationship with the Peierls distortion, as crystalline Bi takes A7 structure. A recent ab initio molec- ular dynamics simulation for liquid Bi predicted a flat-topped profile of the acoustic dispersion curve. To confirm the prediction, we have carried out inelas- tic x-ray scattering (IXS) for liquid Bi. The dynamic structure factor obtained by the IXS exhibits a distinct inelastic excitation of the longitudinal acoustic mode up to 14 nm −1 and the dispersion curve of the excitation energy obtained by the memory function analysis becomes a flat-topped one. We found that a linear chain model including the interatomic interaction with the second near- est neighbors can explain the flat-topped profile. The result suggests that the anomalous dispersion curve in liquid Bi arises from local anisotropy related to the Peierls distortion in the crystalline phase. .
Highlights
Bi belongs to the same group as As in the periodic table of elements, and the local structure of liquid Bi has been discussed from a view-point of the Peierls distortion [1]
The present results suggest that a flat-topped dispersion curve observed in liquid Bi can be explained by taking the interatomic force between the second nearest neighbors into account
Local structure may be distorted in a liquid if a distortion makes the electronic energy lowered, as the case of liquid Bi
Summary
Bi belongs to the same group as As in the periodic table of elements, and the local structure of liquid Bi has been discussed from a view-point of the Peierls distortion [1]. An ab initio molecular dynamics (AIMD) simulation for liquid Bi [7] revealed that longer and shorter bonds produce a distinct shoulder at the first peak in S (Q). Atomic dynamics in liquid Bi had been studied by inelastic neutron scattering (INS) experiments. Sani et al [8] carried out INS experiments at Q ≤ 6 nm−1 and reported the dynamic structure factor S (Q, E), where E is energy transfer, with good statistics. The S (Q, E) exhibits the inelastic excitations of the acoustic mode dispersing with Q. Later Dzugutov and Dahlborg [5] reported that there appears no distinct acoustic excitation at Q > 6 nm−1 with a classical molecular dynamics simulation (CMD), consistent with the INS results by Dahlborg and Olsson
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