Atomic structure at the nanoscale: a 21st century materials challenge

25 September 2009

Emil S. Bozin

Applied Physics and Applied Mathematics Department, Columbia UniversityCondensed Matter Physics and Material Science Department, BNL

Workshop on Characterization of Advanced Materials under Extreme Environments for Next Generation Energy Systems

September 25-26, 2009

Pb (s.g. Fm-3m)

3.479

4.920

6.026

6.958

Complex nanostructured materials

Images: Igor Levin/Tom Pinnavaia/Sandra Rosenthal

Nanoporous (mesoporous) materials

NanoparticlesNanostructured bulk crystals

INT

RO

- Complex bulk systems with interesting physical properties are often inhomogeneous on a nanometer lengthscale

high-temperature superconductors, colossal magnetoresistive materials,

high performance thermoelectric materials …

- Nano-particles, nano-tubes, nano-wires etc. important for applications optoelectronics, nanosensors, programmed release drug delivery systems…

Physical properties often critically depend on the nano-scale structure, rather than the long-range structure!

Crystallography gives average structureR

OU

TIN

E

Figures: J.S.O. Evans et al.

and M. Tucker et al.

Bragg peak info ONLY

Rietveld method

in powders

Example: Ho2(Ti2‑xHox)O7-x/2 ”stuffed spin ice” 300K neutron diffraction patterns (GPPD, IPNS, Argonne)

x=0.00x=0.30x=0.50x=0.67

pyrochlore fluorite

x=0.3

Crystallography challenged: materials w/ disorderC

HA

LLE

NG

E

Rietveld approach assumption: crystals are perfectly periodic…

…but this is not always the case!

Crystallography challenged: nano-crystalsC

HA

LLE

NG

E

Figures: J.S.O. Evans et al.

and M. Tucker et al.

Bragg peak info ONLY

Rietveld method

in powders

Global ApproachF

UT

UR

E

• Add complementary information– Extra experimental data– Theoretical constraints

Science, 316, 561 (2007).

What is PDF?

5.11Å4.92Å

4.26Å

3.76Å

2.84Å

2.46Å

1.42Å

Pair distribution function (PDF) gives the probability of finding an atom at a distance “r” from a given atom.

AP

PR

OA

CH

Pair Distribution Function Method: Applicability

- Originally: short range order in liquids and glasses

- Since late 1980’s: disorder in crystalline materials

- Recently: nanocrystalline materials

Lanthanum Aluminate glass

J. Du and L.R. Corales, J. Non-Cryst. Solids (2007)

AP

PR

OA

CH

Th. Proffen et al, Los Alamos Science (2006)

Gold: bulk vs nanoparticle

Raw data

Structure function

QrdQQSQrG sin]1)([2

)(0

PDF

Pair Distribution Function from total scattering experimentsA

PP

RO

AC

H

Bragg intensity → long range order

Diffuse intensity →short range order

How can we get short range structural information?

0

)sin(]1)([2

)( dQQrQSQrG

Pair Distribution Function from total scattering experimentsA

PP

RO

AC

H

short range informationintermediate range information

Strength of the Pair Distribution Function

Pair Distribution Function: info on different lengthscalesA

PP

RO

AC

H

PDF primer: C60

Pair Distribution Function: info on different lengthscalesA

PP

RO

AC

H

Pair Distribution Function: Q-space resolution effectA

PP

RO

AC

H

Rapid Acquisition PDF (RAPDF) at a synchrotoron: Measuring PDFs in a few seconds

P. Chupas et al, J. Appl. Cryst. 36, 1342-1347 (2003).

Pair Distribution Function: rapid data collection modeA

PP

RO

AC

H

Time-resolved PDF measurements:

Reduction of PtIV Pt0

P. Chupas et al, J. Appl. Cryst. 40, 463-470 (2007).

Application of a large-area, high-sensitivity, fast readout, flat-panel GE detector based on an amorphous silicon

Nickel data, 0.03s collection time, Qmax 28 Å-1

Pair Distribution Function: rapid data collection modeA

PP

RO

AC

H

Ni300K Ni data from GPPD at IPNS, ANL

data

difference

model

PDF Programs

PDFgetX1

PDFgetN1

PDFgui2 (PDFfit)1 http://nirt.pa.msu.edu2 http://www.diffpy.org/

Pair Distribution Function: modelingA

PP

RO

AC

H

Nanometer scale structure of CuIr2S4

Local structural aspects of the metal-insulator transition

in CuIr2S4

- X-ray total scattering study -

Collaboration with: J.F. Mitchell, MSD, Argonne Nat. Lab.

Credits: Y.S. Hor, A.S. Masadeh, H.J. Kim, P. Juhas, S.J.L. Billinge

HIG

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The role of lattice geometry – frustrationSpinel structure: AB2X4

Crystallizes in the cubic (isometric) crystal system

B-sublattice – pyrochlore – corner-shared tetrahedra

This sublattice promotes frustration, interesting physics arises in spin (AF

interactions) and charge (half-integer valence) sectors!

MgAl2O4

X sitesB octahedral sites

A tetrahedral sites

Thiospinel CuIr2S4

At ~226 K it exhibits electronic, magnetic & structural transitions

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Thiospinel CuIr2S4 properties: structural transition

- in-situ TEM micrographs

W. Sun et al., J. Phys.l Soc. Jpn., 70, 2817 (2001).

- Electron diffraction

- TS226K

Tetragonal I41/amd

Cubic Fd-3m

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Thiospinel CuIr2S4 properties

- Metallic at high T- Insulating at low T

- TMI226K

PES, NMR, LDA:

Cu1+ Ir3.5+ (half-integer!)

PES of the insulating phase:

~0.1 eV gap near EF

Ir 5d DOS strongly distorted

T. Furubayashi et al., Solid State Comm. 126, 617 (2003).

S. Nagata et al., Physica B. 194, 1077 (1994).

J. Matsuno et al., Phys. Rev. B. 55, R15979 (1997).

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Thiospinel CuIr2S4 properties

- High T: Pauli paramagnetic- Low T: nonmagnetic

(NMR, Mössbauer, magnetic susceptibility)

T. Furuyabashi et al., J. Phys. Soc. Japan. 63, 3333 (1994).

Ir8S24 octamer

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CuIr2S4: background information

D.I. Khomskii and T. Mizokawa,

PRL 94, 156402 (2005).

Low-T structureRed octahedra Ir3+

Blue octahedra Ir4+

P.G. Radaelli et al.,

Nature 416, 155 (2002).

- Metal at high temperature (Ir is nominally 3.5+)- Insulator at low temperature (Ir’s are 3+ AND 4+)

- T-induced Metal-Insulator transition at ~226K

- Charge ordering and spin dimerization at low-T - Long range charge ordered patterns of isomorphic

octamers- Associated structural change (Peierls distortion)- Ir4+: short Ir-Ir distances appear (~3.0Å) - DIMER- Ir3+: no short Ir-Ir distances (~3.5Å)

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Reduced dimensionality due to specifics of xy-orbitals

CuIr2S4

D.I. Khomskii, Physica Scripta 72, CC8-14 (2005)

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CuIr2S4: effect of x-ray irradiation

V. Kiryukhin et al.,

PRL 97, 225503 (2006).

Cubic Fd-3m

Triclinic P-1

Tetragonal I41/amd

Long range ordered dimersIC C

Insulator Metal

Tetragonal I41/amd

- Incommensurate (IC) short range state below ~40K

- Commensurate (C) short range state 40K<T<~100K

Melting of LRO dimers at low T!

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CuIr2S4: effect of x-ray irradiation

T. Furubayashi et al., Solid State Comm. 126, 617 (2003).

V. Kiryukhin et al.,

PRL 97, 225503 (2006).

Cubic Fd-3m

Triclinic P-1

Tetragonal I41/amd

Long range ordered dimers

When x-ray irradiatedno long range ordered

dimersIC C

Insulator Metal

- Incommensurate (IC) short range state below ~40K

- Commensurate (C) short range state 40K<T<~100K

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CuIr2S4: local structure view of Metal-Insulator transition

Issues:Do the dimers survive locally when the

long range order is removed by:

(1) temperature(2) Cr-doping (3) x-ray irradiation

Total Scattering Approach:• Crystallography – sensitive

to long range ordered dimers• Atomic PDF – sensitive to

presence of dimers

Cubic Fd-3m

Triclinic P-1

Tetragonal I41/amd

Long range ordereddimers

no long range ordereddimers

IC C

Insulator Metal

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Neutron PDF experiment: Ir resonance issueH

IGH

LIG

HT

CuIr2S4: T-driven Metal-Insulator transition

30s

Dramatic changes observed in the local structure, consistent with crystallography (T=10K)R. Endoh et al.,

PRB 68, 115106 (2003).

Compare the case where the MI

transition is not crossed! (T=10K)

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Structure of LaMnO3 across the JT-transition at 720 K

30s

Distortions persist locally!

700 K data (blue) vs 750 K data (red)

LaMnO3: utilizing intuitiveness of PDF - simplicity

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CuIr2S4: T-driven Metal-Insulator transition

30s

Dramatic changes observed in the local structure, consistent with crystallography (T=10K)R. Endoh et al.,

PRB 68, 115106 (2003).

Compare the case where the MI

transition is not crossed! (T=10K)

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CuIr2S4: Hysteretic structural behavior observed

Phase 2: Triclinic P-1 @180 K

Phase 1: Cubic Fd-3m @230 K

Fraction of dimerized sample from 2-phase fit

R. Endoh et al.,

PRB 68, 115106 (2003).HIG

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CuIr2S4: Cr-doping driven Metal-Insulator transition (5% Cr-doping)

30s

Dimers disappear locally when Insulator-Metal transition is invoked by Cr-doping at 200K

R. Endoh et al.,

PRB 68, 115106 (2003).

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CuIr2S4: Melting the long range ordered dimerization pattern by x-rays

0.5s 1s

30s0.5s

MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s

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CuIr2S4: Melting the long range ordered dimerization pattern by x-rays

0.5s 1s

30s0.5s

MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s

HIG

HLI

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CuIr2S4: Melting the long range ordered dimerization pattern by x-rays

0.5s 1s

30s0.5s

MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s

HIG

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CuIr2S4: Melting the long range ordered dimerization pattern by x-rays

0.5s 1s

30s0.5s

MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s

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30s0.5s

Melting observed in present study is approximately order of magnitude “faster” than that in the earlier reports

H. Ishibashi et al., PRB 66, 144424 (2002).

CuIr2S4: Melting the long range ordered dimerization pattern by x-rays

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15s

30s0.5s

Cumulative

Data

Collection

exposure

collection

Continuous

Exposure

CuIr2S4: Melting the long range ordered dimerization pattern by x-rays – local aspects

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15s

30s0.5s

Collection: 250 msec snapshot

Exposure: continuous 23 sec

Snapshot

Data

Collection

exposure

collection

23 sec

Differences due to statistics only,

the underlying local structures are the same!

CuIr2S4: Melting the long range ordered dimerization pattern by x-rays – local aspects

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Diffraction

patterns

(long range order)

PDF

profiles

(short range order)

Temperature Doping Irradiation

CuIr2S4: Melting the long range ordered dimerization pattern – overview

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CuIr2S4 thiospinel: Summary

Do the dimers survive locally when the long range order is removed by:

1. Temperature: NO: the local dimers are destroyed Fraction of the sample that is dimerized has been mapped out through the

hysteretic phase transition2. Cr-doping: NO: the local dimers are destroyed3. x-ray irradiation: YES: the local dimers survive

98keV x-rays also melt the long range order but the melting is faster than previous reportsLong range order recovers quickly at 100K as previously observed

Total Scattering Approach:• Crystallography – sensitive to long range order dimers• Atomic PDF – sensitive to presence of dimers• Dimer peaks clearly resolved and visible

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Acknowledgements• People:Simon Billinge

(Columbia/BNL)

Adam DeConinck (MSU)

Pavol Juhas (Columbia)

Xiangyun Qiu (MSU, now at NIH)

Marek Schmidt (MSU/ISIS, now at Polish Academy of Sciences)

Hyunjeong Kim (LANSCE)

Ahmad Masadeh (MSU, now at University of Jordan)

Gianluca Paglia (MSU, now in industry, Australia)

Thomas Proffen (LANSCE, Los Alamos)

John Mitchell (MSD, Argonne)

Tapan Chatterji (ILL, Grenoble, FR)

Paolo Radaelli (ISIS, UK)

Peter Chupas, Douglas Robinson (APS, Argonne)

• Facilities:Advanced Photon Source, ArgonneIntense Pulsed Neutron Source, ArgonneLos Alamos Neutron Scattering CenterISIS, Rutherford Appleton Laboratory

• Funding: NSF DMR 0304349, DOE DE-AC02-06CH11375, DOE DE-AC52-06NA25396, DOE DE-AC02-98CH10886.

Thank you!