Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analytical Gradients for Nuclear-Electronic Orbital Time-Dependent
  Density Functional Theory: Excited State Geometry Optimizations and Adiabatic
  Excitation Energies   The computational investigation of photochemical processes often entails the
calculation of excited state geometries, energies, and energy gradients. The
nuclear-electronic orbital (NEO) approach treats specified nuclei, typically
protons, quantum mechanically on the same level as the electrons, thereby
including the associated nuclear quantum effects and non-Born-Oppenheimer
behavior into quantum chemistry calculations. The multicomponent density
functional theory (NEO-DFT) and time-dependent DFT (NEO-TDDFT) methods allow
efficient calculations of ground and excited states, respectively. Herein, the
analytical gradients are derived and implemented for the NEO-TDDFT method and
the associated Tamm-Dancoff approximation (NEO-TDA). The programmable equations
for these analytical gradients, as well as the NEO-DFT analytical Hessian, are
provided. The NEO approach includes the anharmonic zero-point energy and
density delocalization associated with the quantum protons, as well as vibronic
mixing, in geometry optimizations and energy calculations of ground and excited
states. The harmonic zero-point energy associated with the other nuclei can be
computed via the NEO Hessian. This approach is used to compute the 0-0
adiabatic excitation energies for a set of nine small molecules with all
protons quantized, exhibiting slight improvement over the conventional
electronic approach. Geometry optimizations of two excited state intramolecular
proton transfer systems are performed with one and two quantized protons,
respectively. The NEO calculations for these systems produce electronically
excited state geometries with stronger intramolecular hydrogen bonds and
similar relative stabilities compared to conventional electronic methods. This
work provides the foundation for nonadiabatic dynamics simulations of
fundamental processes such as photoinduced proton transfer and proton-coupled
electron transfer.

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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga