Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Natural orbital functional for spin-polarized periodic systems   Natural orbital functional theory is considered for systems with one or more
unpaired electrons. An extension of the Piris natural orbital functional (PNOF)
based on electron pairing approach is presented, specifically, we extend the
independent pair model, PNOF5, and the interactive pair model PNOF7 to describe
spin-uncompensated systems. An explicit form for the two-electron cumulant of
high-spin cases is only taken into account, so that singly occupied orbitals
with the same spin are solely considered. The rest of electron pairs with
opposite spins remain paired. The reconstructed two-particle reduced density
matrix fulfills certain N-representability necessary conditions, as well as
guarantees the conservation of the total spin. The theory is applied to model
systems with strong non-dynamic (static) electron correlation, namely, the
one-dimensional Hubbard model with periodic boundary conditions and hydrogen
rings. For the latter, PNOF7 compares well with exact diagonalization results
so the model presented here is able to provide a correct description of the
strong-correlation effects.

36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph