Nearest-neighbor coordination polyhedral clusters in metallic phases defined using Friedel oscillation and atomic dense packing

It is generally difficult to define coordination polyhedral clusters with multi-shelled nearest neighbors. The present work defines their cutoff distances in typical metallic phase structure typesviaFriedel oscillation and atomic dense packing. The nearest neighbors of a cluster are considered to be confined within the first effective Friedel minimum in the pair potential, with the radial distance ratio of the outermost shell to the innermost shell beingrL/rS= 1.5. This ratio is further correlated to atomic radius ratio, facet-capping configuration and cluster coordination number after considering hard-sphere atomic dense packing. The cluster cutoff distance is obtained by multiplying therL/rSratio with the measured innermost shell distance, as is well validated in common cluster types.

DIELECTRIC FUNCTION, FRIEDEL OSCILLATION AND PLASMONS IN WEYL SEMIMETALS

We calculate the dielectric function of a Weyl semimetal at arbitrary momentum q and frequency ω within the random-phase approximation. Taking the static limit, we calculated the Friedel oscillation and found that: (1) For a single Weyl point, the oscillation ~ sin (2kFr)/r4 falls off faster by an 1/r factor than the one in traditional 3D systems ~ cos (2kFr)/r3. This difference arises from the suppression of backward scattering in Weyl fermion systems; (2) For Weyl semimetal with two Weyl points, there are additional oscillations decaying as cos (Q ⋅ r)/r3 and cos (Q ± 2kF) ⋅ r/r3, where Q is the momentum difference between the two Weyl points. We also calculated the plasmon dispersion and found features distinct from those of conventional 3D metals.