Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First-principles theory of frozen-ion flexoelectricity   We demonstrate that the frozen-ion contribution to the flexoelectric
coefficient is given solely in terms of the sum of third moments of the charge
density distortions induced by atomic displacements, even for ferroelectric or
piezoelectric materials. We introduce several practical supercell-based methods
for calculating these coefficients from first principles, and demonstrate them
by computing the coefficients for C, Si, MgO, NaCl, SrTiO$_3$, BaTiO$_3$, and
  PbTiO$_3$. Three important subtleties associated with pseudopotentials, the
treatment of surfaces, and the calculation of transverse components are also
discussed.

18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin