Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Molecular vibrational frequencies from analytic Hessian of constrained
  nuclear-electronic orbital density functional theory   Nuclear quantum effects are important in a variety of chemical and biological
processes. The constrained nuclear-electronic orbital density functional theory
(cNEO-DFT) has been developed to include nuclear quantum effects in energy
surfaces. Herein we develop the analytic Hessian for cNEO-DFT energy with
respect to the change of nuclear (expectation) positions, which can be used to
characterize stationary points on energy surfaces and compute molecular
vibrational frequencies. This is achieved by constructing and solving the
multicomponent cNEO coupled-perturbed Kohn-Sham (cNEO-CPKS) equations, which
describe the response of electronic and nuclear orbitals to the displacement of
nuclear (expectation) positions. With the analytic Hessian, the vibrational
frequencies of a series of small molecules are calculated and compared to those
from conventional DFT Hessian calculations as well as those from the
vibrational second-order perturbation theory (VPT2). It is found that even with
a harmonic treatment, cNEO-DFT significantly outperforms DFT and is comparable
to DFT-VPT2 in the description of vibrational frequencies in regular polyatomic
molecules. Furthermore, cNEO-DFT can reasonably describe the proton transfer
modes in systems with a shared proton, whereas DFT-VPT2 often faces great
challenges. Our results suggest the importance of nuclear quantum effects in
molecular vibrations, and cNEO-DFT is an accurate and inexpensive method to
describe molecular vibrations.

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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: math
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: quant-ph