Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Na4IrO4: Square-Planar Coordination of a Transition Metal in d5
  Configuration due to Weak On-Site Coulomb Interactions   Local environments and valence electron counts primarily determine the
electronic states and physical properties of transition metal complexes. For
example, square-planar surroundings found in transition oxometalates such as
curprates are usually associated with the d8 or d9 electron configuration. In
this work, we address an exotic square-planar mono-oxoanion [IrO4]^{4-} as
observed in Na4IrO4 with Ir(IV) in d^5 configuration, and characterize the
chemical bonding by experiment and ab initio calculations. We find that Na4IrO4
in its ground state evolves a square-planar coordination for Ir(IV) because of
the weak Coulomb repulsion of Ir-5d electrons. In contrast, in its 3d
counterpart, Na4CoO4, Co(IV) is in tetrahedral coordination, due to strong
electron correlation. Na4IrO4 thus may serve as a simple paradigmatic platform
for studying the ramifications of Hubbard type Coulomb interactions on local
geometries.

2
The categories of this paper are: math
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
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The categories of this paper are: eess