Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nature of hyperfine interactions in TbPc$_2$ single-molecule magnets:
  Multireference ab-initio study   Lanthanide-based single-ion magnetic molecules can have large magnetic
hyperfine interactions as well as large magnetic anisotropy. Recent
experimental studies reported tunability of these properties by changes of
chemical environments or by application of external stimuli for device
applications. In order to provide insight onto the origin and mechanism of such
tunability, here we investigate the magnetic hyperfine and nuclear quadrupole
interactions for $^{159}$Tb nucleus in TbPc$_2$ (Pc=phthalocyanine)
single-molecule magnets using multireference ab-initio methods including
spin-orbit interaction. Since the electronic ground and first-excited
(quasi)doublets are well separated in energy, the microscopic Hamiltonian can
be mapped onto an effective Hamiltonian with an electronic pseudo-spin $S=1/2$.
From the ab-initio-calculated parameters, we find that the magnetic hyperfine
coupling is dominated by the interaction of the Tb nuclear spin with electronic
orbital angular momentum. The asymmetric $4f$-like electronic charge
distribution leads to a strong nuclear quadrupole interaction with significant
non-axial terms for the molecule with low symmetry. The ab-initio calculated
electronic-nuclear spectrum including the magnetic hyperfine and quadrupole
interactions is in excellent agreement with experiment. We further find that
the non-axial quadrupole interactions significantly influence the avoided level
crossings in magnetization dynamics and that the molecular distortions affect
mostly the Fermi contact terms as well as the non-axial quadrupole
interactions.

31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ