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# Takeshi Egami <egami@utk.edu>
# requesting 5 days, at minimum=5 days
# beamline 33ID, "Structure of Superconducting Watery Cobaltate"
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# top:/home/www/beamtime-requests/req00436.txt
# UNICAT Member Beam Time Request  #436
# created Fri Aug 15 14:12:52 CDT 2003
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beamline:
	33ID

collaboration:
	Yes

collaborator_Hawoong:
	ON

collaborator_Paul:
	ON

contact:
	egami@utk.edu

days:
	5

description:
	Summary:

	High-energy powder diffraction and medium energy single crystal diffraction will be carried out on Na0.3CoO2&#8226;1.4H2O.  The measurement will complement the neutron scattering results to clarify the detailed structure of this newly discovered superconductor.


Motivation:

	Na0.3CoO2&#8226;1.4H2O is the newest family of transition metal oxide superconductor.  While its critical temperature is low (TC = 4.5 K), cobaltates are closer to the cuprates than other any oxides examined recently, such as ruthenates.  But what is most conspicuous is the presence of water.  The mother compound is NaCoO2, and reduction of Na dopes holes into the CoO2 layers.  The conventional thinking is that H2O provides separation between the CoO2 layers.  Recently we carried out pulsed neutron atomic pair-density function (PDF) analysis on the deutrated compound, and found strong evidence that water is not only separating the CoO2 layers and making the solid more two-dimensional, but actually playing a more active role.  Our results suggest that the water molecules are strongly modified from the usual structure.  While the O-D distance is normal (0.96 Å), the D-D distance is widely distributed from 1.5 to 1.8 Å (the standard distance in the molecule is 1.6 Å).  This result is consistent with the presence of doped on the oxygen of D2O, and suggests that water may be &#8220;metallic&#8221;.  This is a big discovery.

Proposed Experiment:

Experiment 1:
	In order to confirm this story we have to know the structure of CoO2 layer more accurately.  While we see every atom by neutron scattering x-ray is insensitive to H, thus it becomes easier to determine the structure of Na0.3CoO2, separate from the water.  We will carry out a high-energy powder diffraction at 35-40 keV and T = 10 K, and analyze the results both with the Rieveld analysis and the PDF analysis.  The sample is supplied by Brian Sales and Dave Mandrus.  This will take 2 days.

Experiment 2:
	Dave Mandrus and Brian Sales have succeeded in growing a single crystal of this compound.  We will study the diffraction at 12 keV to determine
1.	Na short-range ordering suspected by the powder measurement.
2.	Diffuse scattering due to local displacement, for instance those of oxygen reflecting the Jahn-Teller distortion.  This measurement has to be done at low temperatures.
This measurement will require 3 days.

equipment_required:
	Displex, Ge detector or equivalent.

experiment:
	Structure of Superconducting Watery Cobaltate

foreign_nationals:
	Ference Stercel, Zsolt Marton (they have a badge),
Jin Nakamura (new).

hazards:
	No hazzardous materials.

minimumdays:
	5

name:
	Takeshi Egami

new_request:
	ON

nonmembers:
	

unacceptable_dates:
	

z34ID_details:
	


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