Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamical stability, Vibrational and optical properties of
  anti-perovskite A3BX (Ti3TlN, Ni3SnN and Co3AlC) phases: a first principles
  study   We have investigated various physical properties including phonon dispersion,
thermodynamic parameters, optical constants, Fermi surface, Mulliken bond
population, theoretical Vickers hardness and damage tolerance of
anti-perovskite A3BX phases for the first time by employing density functional
theory (DFT) methodology based on first principles method. Initially we
assessed nine A3BX phases in total and found that only three phases (Ti3TlN,
Ni3SnN and Co3AlC) are mechanically and dynamically stable based on analysis of
computed elastic constants and phonon dispersion along with phonon density of
states. We revisited the structural, elastic and electronic properties of the
compounds to judge the reliability of our calculations. Absence of band gap at
the Fermi level characterizes the phases under consideration as metallic in
nature. The values of Pugh ratio, Poisson ratio and Cauchy factor have
predicted the ductile nature associated with strong metallic bonding in these
compounds. High temperature feasibility study of the phases has also been
performed using the thermodynamic properties, such as the free energy,
enthalpy, entropy, heat capacity and Debye temperature. The Vickers hardness of
the compounds are estimated to be around 4 GPa which is comparable to many
well-known MAX phases, indicating their reasonable hardness and easily
machinable nature. The static refractive index n(zero) has been found around
8.0 for the phases under study that appeals as potential candidate to design
optoelectronics appliances. The reflectivity is found above 44 percent for the
Ti3TlN compound in the energy range of 0 to 14.8 eV demonstrating that this
material holds significant promise as a coating agent to avoid solar heating.

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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
3
The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: alg-geom