<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>X. Chen</dc:contributor>
  <dc:contributor>I-Ming Chou</dc:contributor>
  <dc:contributor>W. Yang</dc:contributor>
  <dc:contributor>Jiawen Hu</dc:contributor>
  <dc:contributor>R.J. Hemley</dc:contributor>
  <dc:contributor>Ho-kwang Mao</dc:contributor>
  <dc:creator>J. Shu</dc:creator>
  <dc:date>2011</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil cells. The diffraction data for types II (sII) and H (sH) were refined to the known structures with space groups&amp;nbsp;&lt;/span&gt;&lt;i&gt;Fd&lt;/i&gt;&lt;span&gt;3&lt;/span&gt;&lt;i&gt;m&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;P&lt;/i&gt;&lt;span&gt;6&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;/&lt;/span&gt;&lt;i&gt;mmc&lt;/i&gt;&lt;span&gt;, respectively. Upon compression, sI methane hydrate transforms to the sII phase at 120&amp;nbsp;MPa, and then to the sH phase at 600&amp;nbsp;MPa. The sII methane hydrate was found to coexist locally with sI phase up to 500&amp;nbsp;MPa and with sH phase up to 600&amp;nbsp;MPa. The pure sH structure was found to be stable between 600 and 900&amp;nbsp;MPa. Methane hydrate decomposes at pressures above 3&amp;nbsp;GPa to form methane with the orientationally disordered&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Fm&lt;/i&gt;&lt;span&gt;3&lt;/span&gt;&lt;i&gt;m&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;structure and ice VII (&lt;/span&gt;&lt;i&gt;Pn&lt;/i&gt;&lt;span&gt;3&lt;/span&gt;&lt;i&gt;m&lt;/i&gt;&lt;span&gt;). The results highlight the role of guest (CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;)-host (H&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O) interactions in the stabilization of the hydrate structures under pressure.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/j.gsf.2010.12.001</dc:identifier>
  <dc:language>en</dc:language>
  <dc:title>Structural stability of methane hydrate at high pressures</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>