First Principles Kinetic Monte Carlo Simulations of Oxygen Interaction with

LaMnO3 Perovskite Surface

Ghanshyam Pilania and R. RamprasadInstitute of Materials Science,

University of Connecticut

MRS Fall Meeting 2011SESSION B10/C6: Joint Session: SOFC Materials Characterization II

Oxygen Interactions with Perovskites: Applications

Chang Hwan Kim, et al. Science 327, 1624 (2010) J. Fleig, Annu. Rev. Mater. Res. 33, 361 (2003). Kudo et al. Chem. Soc. Rev., 2009, 38, 253–278

Sr doped LaMnO3

YSZ

O2

O-2

Triple-phaseboundary

Solid oxide fuel cells

CatalyticConverter

NO oxidation

O2

H2O H2OH2

Photocatalytic H2O splitting

Relevant Elementary Processes

Molecular adsorptionMolecular desorption

Dissociative adsorptionAssociative desorption

Surface dissociationSurface Association

Surface Diffusion

First Principles Thermodynamics (FPT)

O2 covered surface configurations

O covered surface configurations

First Principles Thermodynamics (FPT)

Surf

ace

Ener

gy

Oxygen Chemical Potential

First Principles Thermodynamics

O2#partial#pressure##[log

10(p/p0 )]6

Temperature)(K)-

Clean&surface

partial'coverage'-of'atomic'O

100#%#O#

O2#Condensation##

Limitations of the FPT approach

•Configurational entropy is not taken into account

•Treatment of “large” systems may not be practical

•Metastability can not be captured

•Kinetic aspects

Kinetic Monte Carlo SimulationsMethod Highlights

•DFT fitted 2-D lattice gas Hamiltonian

•Lateral interactions between the adsorbates

•Activation barriers within DFT nudged elastic band Method

•Local environment dependent activation barriers

Kinetic Monte Carlo SimulationsThermodynamic Phase diagram

Saracco, G., Geobaldo, F. (1999). Applied Catalysis B: Environmental.

100%$O

Clean&surface

O2$partial$pressure$$[log

10(p/p0 )]7

Temperature$(K)7

partial'coverage'-of'atomic'O

O2#Condensation##

100#%#O#

O2#partial#pressure##[log

10(p/p0 )]6

Temperature)(K)-

Clean&surface

partial'coverage'-of'atomic'O

100#%#O#

O2#Condensation##

Kinetic Monte Carlo Simulations“Metastable” Phase diagrams

Clean surface

O2#Condensation##

100#%#O#

O+O2

partial'coverage'-of'atomic'O

Starting from a clean surface at any given temperature and pressure.

partial'coverage'-of'atomic'O O2#Condensation##

Clean surface

100#%#O# 100%O2

O+O2

covered

Starting from a clean surface at 100 K and ramping up the temperature at a given

pressure.R. Spinicci et al. Journal of Molecular Catalysis A: Chemical 197 (2003) 147–155

THANKS!BECAT