Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ab initio geometry and bright excitation of carotenoids: Quantum Monte
  Carlo and Many Body Green's Function Theory calculations on peridinin   In this letter we report the singlet ground state structure of the full
carotenoid peridinin by means of variational Monte Carlo (VMC) calculations.
The VMC relaxed geometry has an average bond length alternation of 0.1165(10)
{\AA}, larger than the values obtained by DFT (PBE, B3LYP and CAM-B3LYP) and
shorter than that calculated at the Hartree-Fock (HF) level. TDDFT and EOM-CCSD
calculations on a reduced peridinin model confirm the HOMO-LUMO major
contribution of the Bu+-like (S2) bright excited state. Many Body Green's
Function Theory (MBGFT) calculations of the vertical excitation energy of the
Bu+-like state for the VMC structure (VMC/MBGFT) provide excitation energy of
2.62 eV, in agreement with experimental results in n-hexane (2.72 eV). The
dependence of the excitation energy on the bond length alternation in the MBGFT
and TDDFT calculations with different functionals is discussed.

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The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
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The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom