Local minimum appearing in the interionic pair potentials, when derived from local model pseudopotential, for Al (and some other polyvalent metals) remains as a long standing problem of clear understanding of its origin, although some attempts have been made by a few authors. The origin of this feature of local minimum is systematically investigated for the first time in this paper considering both the core size and the conduction electron density as variables. Interionic pair potential is derived from Ashcroft’s empty core model because it depends on these two variables only. Results of this investigation show monovalent metals do not exhibit a local minimum at all but trivalent Al and some other polyvalent metals do exhibit at their normal densities. Here, the combined effect of the core size and the conduction electron density results whether the local minimum will appear or not. More interestingly, for smaller core size, conduction electron density plays major role and for larger core size the core radius plays the major role in determining the depth of the local minimum.
The effects of parameters used for tuning the interionic pair interaction of the Ashcroft's pseudopotential model on the temperature-dependent atomic transport properties of liquid Al have been studied employing the Universal Scaling Laws (USLs) and Hard Sphere (HS) theories of liquid metals. Temperature-dependent effective HS diameter and excess entropy are the key ingredients of the applied theories. We have calculated them by using Ashcroft's empty core (EMC) pseudopotential and the variational modified hypernetted chain (VMHNC) integral equation theory of liquid. Obtained results clearly suggest that the core radius in the interaction plays a major role in determining atomic transport properties of liquid Al for both USLs and HS theory. It is also observed that USLs are more sensitive than HS theories in response to variation of core radius.
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