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Ph.D. Dissertation Proposal. Physics and Chemistry of ABO 3 Nanostructures from First Principles. Ghanshyam Pilania Chemical, Materials & Biomolecular Engineering Institute of Materials Science University of Connecticut Principal Advisor: Prof. R. Ramprasad

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Physics and Chemistry of ABO 3 Nanostructures from First Principles

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Physics and chemistry of abo 3 nanostructures from first principles

Ph.D. Dissertation Proposal

Physics and Chemistry of ABO3 Nanostructures from First Principles

GhanshyamPilania

Chemical, Materials & Biomolecular Engineering

Institute of Materials Science

University of Connecticut

Principal Advisor: Prof. R. Ramprasad

Associate Advisor: Prof. P. Gao

Associate Advisor: Prof. G. Rossetti, Jr.


Physics and chemistry of abo 3 nanostructures from first principles

ABO3-type Perovskite structure

A

B

O


Physics and chemistry of abo 3 nanostructures from first principles

Outline

Novel polarization states in ABO3 nanowires

“Vortex” v/s “axial” polarization states

Effect of size, surface termination and axial strain on the polarization states

(p,T) surface phase diagrams of ABO3 surfaces

Methodology to construct surface phase diagrams

Calculated (p,T) surface phase diagrams for LaMnO3 and PbTiO3 (001) surfaces

Remaining work

Impact of work


Physics and chemistry of abo 3 nanostructures from first principles

Novel polarization states in ABO3 nanowires


Ferroelectricity in bulk perovskites

Ferroelectricity in bulk perovskites

ABO3 perovskite

ABO3 perovskite

Ferroelectric Well

Energy

Energy

Energy

Energy

P

P

P

P

Paraelectric state

Paraelectric state

Ferroelectric state

Dipole moment per unit volume = Polarization

Ferroelectricity: a collective phenomena

A balance between

long range Coulombic force (favor ferroelectric state)

short range repulsive forces (resist ferroelectric state)

T

Paraelectric

Tc

Ferroelectric


Physics and chemistry of abo 3 nanostructures from first principles

Ferroelectricity in Nanostructures

Bulk

Thin film

+++++++++

Depolarizing

Field

- - - - - - - - -

Ferromagnetic closure domains

C. Kittel, Phys. Rev. 70, 965 1946.

Aguado-Puente et al. (PRL, 2008)


Physics and chemistry of abo 3 nanostructures from first principles

Ferroelectricity in Nanostructures

Closure domain

No depolarizing

Field

No depolarizing

Field

P

P

PFM results indicate possible presence of non-rectilinear polarization in PZT nanodots

Prosendeev & Bellaiche (PRB 2007)

- - -

+ + +

Depolarizing

Field

Rodriguez et al (Nanoletters, 2009)


Abo 3 nanowires our dft study

ABO3 Nanowires – Our DFT Study

Construction of ABO3 nanowires

AO-plane

2x2-AO-terminated

nanowire

BO2-plane

2x2-BO2-terminated

nanowire

AO-plane

BO2-plane


Physics and chemistry of abo 3 nanostructures from first principles

paraelectric

ferroelectric

BaTiO3 Nanowires – Our DFT Study

Axial polarization instability above 1.2 nm

Vortex polarization instability above

1.6 nm

4x4-TiO2

P

4x4-BaO

τ=rxP

Geneste et. al, APL 88, 112906 (2006);


Physics and chemistry of abo 3 nanostructures from first principles

BaTiO3 Nanowires – Experimental Study

Off-axis Polarization in BaTiO3 nanowires

0.8 nm

Spanieret al, NanoLett. 6, 735 (2006)


Pbtio 3 nanowires our dft study

PbTiO3 Nanowires – Our DFT Study

c tetragonal Bulk

Fa

Fa

Fa

4x4-TiO2

Fa

P

acubic Bulk

τ=rxP

P

c (Å)

Fv

P

Unit cell decomposed dipole moments

P

1x1 to 4x4-PbO

Shimada et al, PRB 79, 024102 (2009)


Pbtio 3 nanowires vs terminations strain induced phase transition vortex axial polarization

PbTiO3 Nanowires vs. TerminationsStrain-induced phase transition: vortex  axial polarization

4x4-TiO2-terminated

nanowire

4x4-PbO-terminated

nanowire

Axial compressive Strain

Axial Tensile Strain

[001]

Four possible switchable polarization states

Vortex (clockwise/counter-clockwise), Axial (positive/negative)


Control of polarization states axial strain and surface terminations

Control of polarization statesaxial Strain and surface terminations

PbTiO3 nanowires display switchable rectilinear (axial) and non-rectilinear (vortex) polarization configurations


Physics and chemistry of abo 3 nanostructures from first principles

(T, p) surface phase diagrams of ABO3 systems


Physics and chemistry of abo 3 nanostructures from first principles

Perovskite Surfaces in Catalysis

Why are they important?

Versatility

Flexibility

Less expensive

Thermal stability

Excellent oxygen exchange properties


Physics and chemistry of abo 3 nanostructures from first principles

Sulfur poisoning

Perovskite Surfaces in Catalysis

SO4-2

Dead site

Active site

26 MARCH 2010 VOL 327 SCIENCE

Chang Hwan Kim, Gongshin Qi, Kevin Dahlberg, Wei Li

R. J. H. Voorhoeve, D. W. Johnson, Jr., J. P. Remeika, P. K. Gallagher


Physics and chemistry of abo 3 nanostructures from first principles

Suprafacial v/s Intrafacial


Cubic lamno 3 and pbtio 3 surface phase diagrams

Cubic LaMnO3 and PbTiO3 surface phase diagrams

Surface-O*↔ Surface + ½ O2 (g)


Cubic lamno 3 and pbtio 3 surface phase diagrams1

Cubic LaMnO3 and PbTiO3 surface phase diagrams

+ N/2 O2


Cubic lamno 3 and pbtio 3 surface phase diagrams2

Cubic LaMnO3 and PbTiO3 surface phase diagrams

(1x1) AO-terminated

(1x1) BO2-terminated

A

Formation Energies


Cubic lamno 3 and pbtio 3 surface phase diagrams3

Cubic LaMnO3 and PbTiO3 surface phase diagrams

Relaxed geometries for most favored adsorption sites


Perovskite surfaces in contact with o 2 g

Perovskite surfaces in contact with O2 (g)

Surface-O*↔ Surface + ½ O2 (g)

Assuming ideal gas behavior for O2


Surface phase diagrams for surfaces in contact with o 2

Surface phase diagrams for surfaces in contact with O2

LaMnO3 (001) MnO2-terminated

PbTiO3 (001) TiO2-terminated

100% O ad-atom coverage

100% O ad-atom coverage

log PO2

log PO2

Partial coverage of O ad-atom

T (K)

T (K)

Partial coverage of

O ad-atom

Clean surface

Partial O vacancy

coverage

100% O vacancy

100% O vacancy

Partial O vacancy

coverage


Physics and chemistry of abo 3 nanostructures from first principles

Remaining Work

Effect of surface passivation (by various species such as –OH, H, -CH3 etc.) on polarization states in PbTiO3 nanowires

?

Efield

Electric field response of the vortex polarization state in PbTiO3

nanowires

Dielectric tensor of ferroelectric nanowires

4x4-PbO terminated nanowire (axial polarization)

4x4-TiO2 terminated nanowire (vortex polarization)


Physics and chemistry of abo 3 nanostructures from first principles

Remaining Work

Thermodynamics of environment dependent interaction of various gases on the (001) surface of ABO3 type perovskites

Adsorption site

Equilibrium geometry

Electronic structure

Energetics

NO, NO2, N2, O2

(gases)

Kinetics ??


Physics and chemistry of abo 3 nanostructures from first principles

Impact of Work

0

0

1

0

How to shrink the

hard drive?!!

Non volatile Ferroelectric memory

Potential to increase present memory storage density by five order of magnitude


Physics and chemistry of abo 3 nanostructures from first principles

Impact of Work

DeNOxprocesses

NO + CO + unburned hydrocarbons

LaCoO3 (○)

La0.9Sr0.1CoO3 (●)

CO2

CO

catalytic

converter

CO2+H2O

CnHm

LaMnO3 (□)

N2 + O2

NOx

La0.9Sr0.1MnO3 (■)

commercial DOC (▲)


Physics and chemistry of abo 3 nanostructures from first principles

List of Publications

G. Pilania, S. P. Alpay and R. Ramprasad, "Ab initio study of ferroelectricity in BaTiO3 nanowires", Phys. Rev. B80, 014113(1)-014113(7)- (2009).

G. Pilania, D. Q. Tan, Y. Cao, V. S. Venkataramani, Q. Chen and R. Ramprasad, "Ab initio study of antiferroelectric PbZrO3 (001) surfaces", J. Mater. Sci. 44, 5249-5255 (2009).

G. Pilania, T. Sadowski and R. Ramprasad, "Oxygen adsorption on CdSe Surfaces: A case study of asymmetric anisotropic growth through Ab initio computations", J. Phys. Chem. C. 113(5), 1863-1871 (2009).

J. D. Doll, G. Pilania, R. Ramprasad and F. Papadimitrakopoulos, "Oxygen-Assisted Unidirectional Growth of CdSe Nanorods Using a Low-Temperature Redox Process", Nano Lett., 10 (2), 680-685 (2010).

G. Pilania and R. Ramprasad “Vortex -Polarization Instability in PbTiO3 nanowires”, under review.

G. Pilania and R. Ramprasad “Thermodynamics of environment dependent oxygen adsorption and vacancy formation on cubic PbTiO3 and LaMnO3 (001) surfaces”, In preparation.


Physics and chemistry of abo 3 nanostructures from first principles

Acknowledgments

Committee members:

Profs. Rampi Ramprasad, Puxian Gao and George A. Rossetti, Jr.

Profs. Rainer Hebert and Pamir S. Alpay

Group Members :

Ning, Tang, Tom, Hong, Satyesh, Chenchen, Yenny

Computational resources:

IMS computation clusters; SGI supercomputer in SoE and Teragrid

Funding:

NSF & ONR


Physics and chemistry of abo 3 nanostructures from first principles

Thanks!


Back up slides

Back-up slides


4x4 tio 2 terminated nanowire atomic relaxations in the vortex state

4x4-TiO2 terminated Nanowire Atomic relaxations in the vortex state

4x4-TiO2-terminated

nanowire

[001]


Cubic lamno 3 and pbtio 3 surface phase diagrams4

Cubic LaMnO3 and PbTiO3 surface phase diagrams

∆γ=


Effect of vibrational free energy

Effect of vibrational free energy

(1x1)-MnO2-terminated (001) LaMnO3 surface

O ad-atoms

O vacancies

T (k)

% change in ∆γ

% change in ∆γ

T (k)


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