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SUMMARY:The structural chemistry of nano-FeS and ferrihydrite - John Paris
 e (Dept. Geosciences/Chemistry\, SUNY- Stony Brook)
DTSTART:20100301T160000Z
DTEND:20100301T170000Z
UID:TALK22576@talks.cam.ac.uk
CONTACT:Ian Farnan
DESCRIPTION:Nano-crystalline iron sulfides and oxyhyroxides are implicated
  in a variety of surficial terrestrial\, marine\, and planetary processes\
 , including acid-mine drainage\, martian diagenetic proceses\, pre-biotic 
 catalysis mimicking hydrogenase and nitrogenase\, and the global iron and 
 sulfur cycles. The composition\, single-phase nature and atomic arrangemen
 ts in nano-crystalline “FeS” and ferrihydrite have been controversial 
 for at least 50 years. Contrary to previous reports\, we believe both nano
  “FeS” and ferrihydrite are single phase\, making possible interpretat
 ion of results from sorption on these substrates\, intended to mimic the p
 rocess and global cycles of interest. Considerable debate still surrounds 
 the atomic arrangement in ferrihydrite in particular. A growing body of ev
 idence confirms the composition of ferrihydrite is close to Fe10O14(OH)2. 
 Further\, a single-phase model (SPM) suffices for explanation of the atomi
 c arrangement in inorganically and biologically derived 2- and 6-line vari
 eties. The 50 years of effort expended on studying this material have prod
 uced many inconsistent results\, probably due to variations in preparation
 \, confusion due to over-fitting information poor (low Q\, high incoherenc
 e) diffraction and x-ray absorption data with overly complex models\, etc.
  Careful large-batch synthesis of hydrogenous and deuterated samples\, and
  the use of several analytical probes on these same samples\, provide a co
 nsistent picture.
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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