Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First principles study of stability of MXenes under electron beam   Interactions of two-dimensional MXene sheets and electron beam of (scanning)
transmission electron microscope are studied via first-principles calculations.
We simulated the knock-on displacement threshold for Ti$_3$C$_2$ MXene sheet
via ab initio molecular dynamics simulations and for five other MXenes
(Ti$_2$C, Ti$_2$N, Nb$_2$C, Mo$_2$TiC$_2$, and Ti$_3$CN) approximately from
defect formation energies. We evaluated sputtering cross section and sputtering
rates, and based on those the evolution of the surface composition. We find
that at the exit surface and for "low" TEM energies H and F sputter at equal
rates, but at "high" TEM energies the F is sputtered most strongly. In the
enter surface, H sputtering dominates. The results were found to be largely
similar for all studied MXenes, and although the displacement thresholds varied
between the different metal atoms the thresholds were always too high to lead
to significant sputtering of the metal atoms. We simulated electron microscope
images at the successive stages of sputtering, and found that while it is
likely difficult to identify surface groups based on the spot intensities, the
local contraction of lattice around O groups should be observable. We also
studied MXenes encapsulated with graphene and found them to provide efficient
protection from the knock-on damage for all surface group atoms except H.

35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs