Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Accurate Predictions of Volatile Plutonium Thermodynamic Properties   The ability to predict the nature and amounts of plutonium emissions in
industrial accidents, such as in solvent fires at PUREX nuclear reprocessing
facilities, is a key concern of nuclear safety agencies. In accident conditions
and in the presence of oxygen and water vapor, plutonium is expected to form
the three major volatile species $\rm{PuO_2}$, $\rm{PuO_3}$, and
$\rm{PuO_2(OH)_2}$, for which the thermodynamic data necessary for predictions
(enthalpies of formation and heat capacities) presently show either large
uncertainties or are lacking. In this work we aim to alleviate such
shortcomings by obtaining the aforementioned data via relativistic correlated
electronic structure calculations employing a two-step multi-reference approach
(MS-CASPT2 with SO-RASSI), which is able to describe the multireference
character of the ground-state wave functions of $\rm{PuO_3}$ and
$\rm{PuO_2(OH)_2}$. We benchmark this approach by comparing it to relativistic
coupled cluster calculations for the ground, ionized, and excited states of
$\rm{PuO_2}$. Our results allow us to predict enthalpies of formation
$\Delta_fH^\ominus(\rm{298.15~K})$ of $\rm{PuO_2}$, $\rm{PuO_3}$ and
$\rm{PuO_2(OH)_2}$ to be $\rm{-449.5\pm8.8}$, $\rm{-553.2\pm27.5}$, and
$\rm{-1012.6\pm38.1~kJ\;mol^{-1}}$, respectively, which confirm the
predominance of plutonium dioxide, but also reveal the existence of plutonium
trioxide in the gaseous phase under oxidative conditions, though the partial
pressures of $\rm{PuO_3}$ and $\rm{PuO_2(OH)_2}$ are nonetheless always rather
low under a wet atmosphere. Our calculations also permit us to reassess prior
results for $\rm{PuO_2}$, establishing that the ground state of the
$\rm{PuO_2}$ molecule is mainly of $\rm{^{5}\Sigma_{g}^+}$ character, as well
as to confirm the experimental value for the adiabatic ionization energy of
$\rm{PuO_2}$.

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The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
2
The categories of this paper are: math
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The categories of this paper are: bayes-an