Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relationships Between Atomic Diffusion Mechanisms and Ensemble Transport
  Coefficients in Crystalline Polymorphs   Ionic transport in conventional ionic solids is generally considered to
proceed via independent diffusion events or "hops''. This assumption leads to
well-known Arrhenius expressions for transport coefficients, and is equivalent
to assuming diffusion is a Poisson process. Using molecular dynamics
simulations of the low-temperature B1, B3, and B4 AgI polymorphs, we have
compared rates of ion-hopping with corresponding Poisson distributions to test
the assumption of independent hopping in these common structure-types. In all
cases diffusion is a non-Poisson process, and hopping is strongly correlated in
time. In B1 the diffusion coefficient can be approximated by an Arrhenius
expression, though the physical significance of the parameters differs from
that commonly assumed. In low temperature B3 and B4 diffusion is characterised
by concerted motion of multiple ions in short closed loops. Diffusion
coefficients can not be expressed in a simple Arrhenius form dependent on
single-ion free-energies, and intrinsic diffusion must be considered a
many-body process.

2
The categories of this paper are: math
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th