Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Point-charge electrostatics in disordered alloys   A simple analytic model of point-ion electrostatics has been previously
proposed in which the magnitude of the net charge q_i on each atom in an
ordered or random alloy depends linearly on the number N_i^(1) of unlike
neighbors in its first coordination shell. Point charges extracted from recent
large supercell (256-432 atom) local density approximation (LDA) calculations
of Cu-Zn random alloys now enable an assessment of the physical validity and
accuracy of the simple model. We find that this model accurately describes (i)
the trends in q_i vs. N_i^(1), particularly for fcc alloys, (ii) the magnitudes
of total electrostatic energies in random alloys, (iii) the relationships
between constant-occupation-averaged charges <q_i> and Coulomb shifts <V_i>
(i.e., the average over all sites occupied by either $A$ or $B$ atoms) in the
random alloy, and (iv) the linear relation between the site charge q_i and the
constant- charge-averaged Coulomb shift (i.e., the average over all sites with
the same charge) for fcc alloys. However, for bcc alloys the fluctuations
predicted by the model in the q_i vs. V_i relation exceed those found in the
LDA supercell calculations. We find that (a) the fluctuations present in the
model have a vanishing contribution to the electrostatic energy. (b)
Generalizing the model to include a dependence of the charge on the atoms in
the first three (two) shells in bcc (fcc) - rather than the first shell only -
removes the fluctuations, in complete agreement with the LDA data. We also
demonstrate an efficient way to extract charge transfer parameters of the
generalized model from LDA calculations on small unit cells.

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The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph