Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Behavior of Hexane on Graphite at Near-Monolayer Densities   We present the results of molecular dynamics (MD) studies of hexane
physisorbed onto graphite for eight coverages in the range $0.875 \le \rho \le
1.05$ (in units of monolayers). At low temperatures the adsorbate molecules
form a uniaxially incommensurate herringbone (UI-HB) solid. At high coverages
the solid consists of adsorbate molecules that are primarily rolled on their
side perpen-dicular to the surface of the substrate. As the coverage is
decreased, the amount of molecular rolling diminishes until $\rho$ = 0.933
where it disappears (molecules become primarily parallel to the surface). If
the density is decreased enough, vacancies appear. As the temperature is
increased we observe a three-phase regime for $\rho > 0.933$ (with an
orientationally ordered nematic mesophase), for lower coverages the system
melts directly to the disordered (and isotropic) liquid phase. The
solid-nematic transition temperature is very sensitive to coverage whereas the
melting temperature is quite insensitive to it, except for at low coverages
where increased in-plane space and ultimately vacancies soften the solid phase
and lower the melting temperature. Our results signal the importance of
molecular rolling and tilting (which result from an the competition between
molecule-molecule and molecule-substrate interactions) for the formation of the
intermediate phase, while the insensitivity of the system's melting temperature
to changing density is understood in terms of in-plane space occupation through
rolling. Comparisons and contrasts with experimental results are discussed.

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The categories of this paper are: hep-th
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The categories of this paper are: eess
34
The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: math