Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Piezoelectricity in two-dimensional materials: a comparative study
  between lattice dynamics and ab-initio calculations   Elastic constant C_{11} and piezoelectric stress constant e_{1,11} of
two-dimensional (2D) dielectric materials comprising h-BN, 2H MoS2 and other
transition metal dichalcogenides (TMDCs) and -dioxides (TMDOs) are calculated
using lattice dynamical theory. The results are compared with corresponding
quantities obtained by ab-initio calculations. We identify the difference
between clamped-ion and relaxed-ion contributions with the dependence on inner
strains which are due to the relative displacements of the ions in the unit
cell. Lattice dynamics allows to express the inner strains contributions in
terms of microscopic quantities such as effective ionic charges and
optoacoustical couplings, which allows us to clarify differences in the
piezoelectric behavior between h- BN versus MoS2. Trends in the different
microscopic quantities as functions of atomic composition are discussed.

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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
0
The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg