Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Formation of Polymorphic Cluster Phases for Purely Repulsive Soft
  Spheres   We present results from density functional theory and computer simulations
that unambiguously predict the occurrence of first-order freezing transitions
for a large class of ultrasoft model systems into cluster crystals. The
clusters consist of fully overlapping particles and arise without the existence
of attractive forces. The number of particles participating in a cluster scales
linearly with density, therefore the crystals feature density-independent
lattice constants. Clustering is accompanied by polymorphic bcc-fcc
transitions, with fcc being the stable phase at high densities.

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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
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The categories of this paper are: cs
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex