Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Long term aging of Selenide glasses: Evidence of sub-Tg endotherms and
  pre-Tg exotherms   Long term aging is studied on several families of chalcogenide glasses
including the Ge-Se, As-Se, Ge-P-Se and Ge-As-Se systems. Special attention is
given to the As-Se binary, a system that displays a rich variety of aging
behavior intimately tied to sample synthesis conditions and the ambient
environment in which samples are aged. Calorimetric (Modulated DSC) and Raman
scattering experiments are undertaken. Our results show all samples display a
sub-Tg endotherm below Tg in glassy networks possessing a mean coordination
number r in the 2.25 < r < 2.45 range. Two sets of AsxSe1-x samples aged for 8
years were compared, set A consisted of slow cooled samples aged in the dark,
and set B consisted of melt quenched samples aged at laboratory environment.
Samples of set B in the As concentration range, 35% < x < 60%, display a pre-Tg
exotherm, but the feature is not observed in samples of set A. The aging
behavior of set A presumably represents intrinsic aging in these glasses, while
that of set B is extrinsic due to presence of light. The reversibility window
persists in both sets of samples but is less well defined in set B. These
findings contrast with a recent study by Golovchak et al., which finds the
onset of the reversibility window moved up to the stoichiometric composition (x
= 40%). Here we show that the upshifted window is better understood as
resulting due to demixing of As4Se4 and As4Se3 molecules from the backbone,
i.e., Nanoscale phase separation (NSPS). We attribute sub-Tg endotherms to
compaction of the flexible part of networks upon long term aging, while the
pre-Tg exotherm to NSPS. Finally, the narrowing and sharpening of the
reversibility window upon aging is interpreted as the slow 'self-organizing'
stress relaxation of the phases just outside the Intermediate phase.

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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph