One metal atom surrounded by its 12 nearest neighbors is considered for bothD3d(facehyphen;centered cubichyphen;like) andD3h(hexagonal closehyphen;packedhyphen;like) geometries. For Al and Be, the neutral cluster and the positive and negative ions are considered for idealized (all bonds equal) and distorted geometries. TheD3dgeometry is found to be the lowest for Be13, while theD3hgeometry is lower for Al13. This is the reverse of what is expected based upon the bulk metal structures, Be(hcp) and Al(fcc). Al13is found to have only small distortions, while Be13shows large distortions for both theD3dandD3hgeometries. The ions have geometries which are similar to those found for the neutral systems. Both allhyphen;electron and effective core potential calculations were carried out on the X13clusters; the agreement is very good.
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