Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $\textit{Ab initio}$ evidence for nonthermal characteristics in
  ultrafast laser melting   Laser melting of semiconductors has been observed for almost 40 years;
surprisingly, it is not well understood where most theoretical simulations show
a laser-induced thermal process. $\textit{Ab initio}$ nonadiabatic simulations
based on real-time time-dependent density functional theory reveal intrinsic
nonthermal melting of silicon, at a temperature far below the thermal melting
temperature of 1680 K. Both excitation threshold and time evolution of
diffraction intensity agree well with experiment. Nonthermal melting is
attributed to excitation-induced drastic changes in bonding electron density,
and the subsequent decrease in the melting barrier, rather than lattice heating
as previously assumed in the two-temperature models.

20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin