Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A real-time time-dependent density functional tight-binding
  implementation for semiclassical excited state electron-nuclear dynamics and
  pump-probe spectroscopy simulations   The increasing need to simulate the dynamics of photoexcited molecular and
nanosystems in the sub-picosecond regime demands new efficient tools able to
describe the quantum nature of matter at a low computational cost. By combining
the power of the approximate DFTB method with the semiclassical Ehrenfest
method for nuclear-electron dynamics we have achieved a real-time
time-dependent DFTB (TD-DFTB) implementation that fits such requirements. In
addition to enabling the study of nuclear motion effects in photoinduced charge
transfer processes, our code adds novel features to the realm of static and
time-resolved computational spectroscopies. In particular, the optical
properties of periodic materials such as graphene nanoribbons or the use of
corrections such as the "LDA+U" and "pseudo SIC" methods to improve the optical
properties in some systems, can now be handled at the TD-DFTB level. Moreover,
the simulation of fully-atomistic time-resolved transient absorption spectra
and impulsive vibrational spectra can now be achieved within reasonable
computing time, owing to the good performance of the implementation and a
parallel simulation protocol. Its application to the study of UV/visible
light-induced vibrational coherences in molecules is demonstrated and opens a
new door into the mechanisms of non-equilibrium ultrafast phenomena in
countless materials with relevant applications.

16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
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The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con