The UWXAFS analysis package: philosophy and details

Stern, Edward A.; Newville, Matthew; Ravel, Bruce; Yacoby, Y.; Haskel, D.

doi:10.1016/0921-4526(94)00826-h

Cited by 853 publications

(635 citation statements)

References 9 publications

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“…In particular, pair distances, r i , and pair-distance distribution widths, σ 2 i , can be obtained for the first few atomic shells, i, out to about 5Å. These XAFS data were analyzed using the UWXAFS package 28 . First, the XAFS function χ = µ/µ 0 − 1 is extracted after determining the atomic background absorption, µ 0 , obtained with the UWXAFS program AUTOBK by passing a cu- bic spline through the absorption data, µ.…”

Section: Resultsmentioning

confidence: 99%

“…Additional details of the XAFS analysis and the determination of the uncertainty of parameters have been given elsewhere. 28,30 The σ 2 data were analyzed analogously to the NPD u 2 parameters described above, except that a correlatedDebye model 32,33 was used to account for correlated motion/displacements of the atom pairs. This model for σ 2 is the same as the Debye model (Eq.…”

Section: Resultsmentioning

confidence: 99%

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Structural properties of the geometrically frustrated pyrochloreTb2Ti2O
Han
¹
,
Gardner
²
,
Booth
³

2004
Phys. Rev. B
51
3
32
0
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Although materials that exhibit nearest-neighbor-only antiferromagnetic interactions and geometrical frustration theoretically should not magnetically order in the absence of disorder, few such systems have been observed experimentally. One such system appears to be the pyrochlore Tb2Ti2O7. However, previous structural studies indicated that Tb2Ti2O7 is an imperfect pyrochlore. To clarify the situation, we performed neutron powder diffraction (NPD) and x-ray absorption fine structure (XAFS) measurements on samples that were prepared identically to those that show no magnetic order. The NPD measurements show that the long-range structure of Tb2Ti2O7 is well ordered with no structural transitions between 4.5 and 600 K. In particular, mean-squared displacements (u 2 's) for each site follow a Debye model with no offsets. No evidence for Tb/Ti site interchange was observed within an upper limit of 2%. Likewise, no excess or deficiency in the oxygen stoichiometry was observed, within an upper limit of 2% of the nominal pyrochlore value. Tb LIIIand Ti K-edge XAFS measurements from 20-300 K similarly indicate a well-ordered local structure. Other aspects of the structure are considered. We conclude that Tb2Ti2O7 has, within experimental error, an ideal, disorder-free pyrochlore lattice, thereby allowing the system to remain in a dynamic, frustrated spin state to the lowest observed temperatures.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Structural properties of the geometrically frustrated pyrochloreTb2Ti2O
Han
¹
,
Gardner
²
,
Booth
³

2004
Phys. Rev. B
51
3
32
0
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show abstract

“…The analysis of the observed absorption spectra was done following the standard FEFF procedure [6,7] including the background treatment with AUTOBK [8].…”

Section: Methodsmentioning

confidence: 99%

Local structure around Mn in Mn containing ZnO nanocrystals

Koteski¹,

Zhou

Farangis

et al. 2007

Physica Status Solidi (b)

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Published online zzz PACS 61.72. Vv, 61.46.Hk, 61.10.Ht Among the diluted magnetic semiconductors of current interest, especially ZnO is experiencing a renaissance with the incorporation of Mn because of the recent predictions from theory. We have obtained local structure information from X-ray Absorption Spectroscopy (XAS) complementing previous electron paramagnetic resonance (EPR) studies on Mn in ZnO nanocrystals and Zn(OH) 2 . Mn is found to be incorporated substitutionally into the ZnO nanocrystals with a sizeable distortion as compared to the regular ZnO lattice structure. Depending on the preparation of the nanocrystals Mn is found in the ZnO core as well as in a Zn(OH) 2 surface shell with a fraction which decreases upon annealing as the shell disintegrates forming additional ZnO. No indications for Mn clusters were found.

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“…The analysis of the observed absorption spectra was done following the standard FEFF procedure [7,8] including the background treatment with AUTOBK [9].…”

Section: Methodsmentioning

confidence: 99%

Experimental Verification of Calculated Lattice Relaxations Around Impurities in CdTE

et al. 2004

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We have measured the lattice distortion around As (acceptor) and Br (donor) in CdTe with fluorescence detected X-ray absorption spectroscopy. We could experimentally verify the lattice relaxation with a bond length reduction of 8% around the As atom as inferred indirectly from ab initio calculations of the electric field gradient performed with the WIEN97 package in comparison with the measured value in a Perturbed Angular Correlation experiment as recently reported. We have complemented our own calculations of relaxation with WIEN97 with calculations using the FHI96md pseudo-potential program which allows the use of larger super-cell sizes. Encouraged by the good agreement between experiment and model calculation for As in CdTe as well as similarly for the isovalent Se in CdTe, we extended our investigation to Br in CdTe, where the electric field gradient has also been measured, and could not only verify the derived lattice expansion around Br with our EXAFS analysis but additionally observe fractions of Br in the A-center as well as in a DX-center configuration.

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The UWXAFS analysis package: philosophy and details

Cited by 853 publications

References 9 publications

Structural properties of the geometrically frustrated pyrochloreTb2Ti2O
Han
¹
,
Gardner
²
,
Booth
³

2004
Phys. Rev. B
51
3
32
0
View full text Add to dashboard Cite

Structural properties of the geometrically frustrated pyrochloreTb2Ti2O
Han
¹
,
Gardner
²
,
Booth
³

2004
Phys. Rev. B
51
3
32
0
View full text Add to dashboard Cite

Local structure around Mn in Mn containing ZnO nanocrystals

Experimental Verification of Calculated Lattice Relaxations Around Impurities in CdTE

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The UWXAFS analysis package: philosophy and details

Cited by 853 publications

References 9 publications

Structural properties of the geometrically frustrated pyrochloreTb2Ti2OHan1, Gardner2, Booth3 2004Phys. Rev. B513320View full textAdd to dashboardCite

Structural properties of the geometrically frustrated pyrochloreTb2Ti2OHan1, Gardner2, Booth3 2004Phys. Rev. B513320View full textAdd to dashboardCite

Local structure around Mn in Mn containing ZnO nanocrystals

Experimental Verification of Calculated Lattice Relaxations Around Impurities in CdTE

Contact Info

Product

Resources

About

Structural properties of the geometrically frustrated pyrochloreTb2Ti2O
Han
¹
,
Gardner
²
,
Booth
³

2004
Phys. Rev. B
51
3
32
0
View full text Add to dashboard Cite

Structural properties of the geometrically frustrated pyrochloreTb2Ti2O
Han
¹
,
Gardner
²
,
Booth
³

2004
Phys. Rev. B
51
3
32
0
View full text Add to dashboard Cite