Sodium Trimer Ordering on NaxCoO2 Surface

Abstract

Sodium ion ordering on in situ cleaved NaxCoO2 (x=0.84) surface has been studied by ultra high vacuum scanning tunneling microscopy (UHV-STM) at room temperature. Three main phases, with p(3x3), (root 7 x root 7), and (2 root 3 x 2 root 3) hexagonal unit cells and surface Na concentration of 1/3, 3/7, 1/2, respectively, were identified. One surprising finding is that Na trimers act as the basic building blocks that order in long range. The stability of Na trimers is attributed to the increased Na coordination with oxygen as indicated by ab initio calculations, and possibly at finite temperature by configuration entropy.

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Cited by in corpus (4)

• Sodium vacancy ordering and the co-existence of localized spins and itinerant charges in NaxCoO2
• 59Co NMR evidence for charge and orbital order in the kagome like structure of Na2/3CoO2
• Crystal-to-stripe reordering of sodium ions in NaxCoO2 (x>=0.75)
• Rearrangement of Sodium ordering and its effect on physical properties in $N{a}_{x}Co{O}_2$ system