Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First-principles study of structural, elastic, and bonding properties of
  pyrochlores   Density Functional Theory calculations have been performed to obtain lattice
parameters, elastic constants, and electronic properties of ideal pyrochlores
with the composition A$_2$B$_2$O$_7$ (where A=La,Y and B=Ti,Sn,Hf, Zr). Some
thermal properties are also inferred from the elastic properties. A decrease of
the sound velocity (and thus, of the Debye temperature) with the atomic mass of
the B ion is observed. Static and dynamical atomic charges are obtained to
quantify the degree of covalency/ionicity. A large anomalous contribution to
the dynamical charge is observed for Hf, Zr, and specially for Ti. It is
attributed to the hybridization between occupied $2p$ states of oxygen and
unoccupied d states of the B cation. The analysis based on Mulliken population
and deformation charge integrated in the Voronoi polyhedra indicates that the
ionicity of these pyrochlores increases in the order Sn--Ti--Hf--Zr. The charge
deformation contour plots support this assignment.

13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con