Quantum Theory Calculations of Supported Transition-Metal

Clusters

Dr. Yohanna Seminovski Perez, Dr. Polina Tereshchuk,

Prof. Dr. Juarez L. F. Da Silva

QTNano Quantum Theory of Nanomaterials Group São Carlos Institute of Chemistry

University of São Paulo

Members:-Prof. Dr. Juarez L. F. Da Silva

-Posdocs: Dr. Yohanna Dr. Polina Dr. Anderson S. Seminovski Tereshchuk Chaves

-PhD students: Rafael L.H. Diego G. Fernando P. Celso R. Freire Sobrinho Sabino Rego

-Msc students: Larissa Z. Israel Douglas G. Rafael Besse Rosalino de Souza Besse

Computational Resources: - Local SGI cluster

- LCCA Aguia cluster- USP-Rice Bluegene

Collaborators: - Prof. Dr. Adam Kiejna, U. Wrocław, Poland- Prof. Dr. Maurício J. Piotrowski, UFPel, Brazil- Prof. Dr. Luiz Nunes de Oliveira, IFSC, USP, Brazil - Prof. Dr. Marcelo Falcão de Oliveira, EESC, USP, Brazil

Quantum Theory of Nanomaterials Group

Research Projects

Clusters and Nanoclusters- Transition-metals.- Oxides and binary systems.

- Global optimization algorithms.- Thermodynamic properties.

Surfaces- Clean surface properties.- Transition-metal supported on surfaces.- Molecular adsorption on surfaces.

Solids- Transparent conducting oxides.- Wide-band gap semiconductors.

Computational Details

Density Functional Theory – DFT- Semilocal XC functionals: PBE, PW91.- Hybrid functionals: PBE0, HSE.- Orbital dependent LDA+U functional.- van der Waals corrections (S. Grimme, TS-SCS).- Spin-orbit coupling for valence states.

Kohn-Sham equations- Plane waves: VASP.- Numeric atom-centered basis functions: FHI-AIMS.

Local and Global optimizations algorithms - GOP- Revised Basin Hopping Monte Carlo – RBHMC.- Genetic Algorithm - GA.

Importance and Challenges of TM/CeO2(111) supports

● This interfacial interaction can be theoretically described.

Importance and Challenges of TM/CeO2(111) supports are related with Ce atom:

● The conditions in which this happens are going to be described using DFT+U approach.

● In VASP DFT code, we used an effective U, Ueff=4.5 eV within the Dudarev approach of DFT+U.

CeO2 Metal Oxide Support

TM Cluster

BSASBS

● TM/CeO2(111) supports have a characteristic synergistic effect useful for catalysis of

reactions.

Interface

Synergy

Ce-4f valence state is delocalized in unreduced CeO2 (111), but

these states can also allocate strongly correlated localized charges.

TM4/CeO

2(111): 2D vs. 3D TM over CeO

2

Ru4/CeO

2 (111)

Rh4/CeO

2 (111)

Os4 /CeO

2 (111)

Ir4 /CeO

2 (111)

Pd4/CeO

2 (111)

Pt4/CeO

2 (111)

Ag4 /CeO

2 (111)

Au4 /CeO

2 (111)

M.J. Piotrowski, P. Tereshchuk, J.L.F. Da Silva, J. Phys Chem C 118 (2014) 21438

2D-Monolayer

- In TM 2D-Monolayer: there is an equidistant CeIII generation. - In TM 3D-Cluster: Generation of one CeIII for Pt and Pd and two for Au and Ag.

3D-Cluster

Transition Metal of group 6 and 7Partially filled d-orbitals

Transition Metal of group 8 and 9Almost completelyfilled d-orbitals

For Pd and Pt cases (8 group):

For Au and Ag (9 group):

For Ru,Rh,Os and Ir:

Pt4/CeO

2(111): Electronic structure

electronic LDOS of CeIII statesTM states hibridized with O states

M.J. Piotrowski, P. Tereshchuk, J.L.F. Da Silva, J. Phys Chem C 118 (2014) 21438

P. Tereshchuk, R.L.H. Freire, C.G. Ungureanu, Y. Seminovski, A. Kiejna, J.L.F. Da Silva, Phys. Chem. Chem. Phys. (2015) DOI: 10.1039/C4CP06016D

13-atoms TM-clusters (TM13

)

A 4x4 unit-cell of unreduced CeO

2 (111) surface

● CeIII are slightly bigger than CeIV creating some strains in the surface.

3D-Pyramidal structure 2D-Structures

TM13

/CeO2(111): 2D vs. 3D TM over CeO

2

3 CeIII are located in the topmost Ce layer.

TM13

of Ag, Au, Pt and Pd show a pyramid like structure as the most stable.

Calculations:

Erel= Most stable Erel=

Flow of electronic charges on TM13

/CeO2(111)

TM13

-cluster stacking: TM/TM

4/TM

8/CeO

2(111)

P. Tereshchuk, R.L.H. Freire, C.G. Ungureanu, Y. Seminovski, A. Kiejna, J.L.F. Da Silva, Phys. Chem. Chem. Phys. (2015) DOI: 10.1039/C4CP06016D

3- Ce f-states change from itinerant to localized(from CeIV to CeIII)

4- Important to notice is that the pressure of the TM

13-

clusters decreases the charge of the underlying O-ions and increases in the remaining O-ions.

e-e-e-

1- Flow of electronic charge from TM

13 cluster to CeO

2

(111) due to electronegativity-difference.

2- Induce a change in the oxidation-state of 3 Ce-atoms in the topmost-Ce layer.

● In TM

4/CeO

2 (111) the 2D and 3D TM structures have an atomic

arrangement due to the interaction with the surface, which electronic LDOS shows TM states hibridized with the O states and also the formation of localized CeIII.

● In TM

13/CeO

2 (111) there is a formation of a pyramid-like structure

with a TM/TM4/TM

8/CeO

2(111) stacking in which the charges flow

from the TM8-layer to the CeO

2(111) surface and the effective-

cationic-charge change in 3 Ce-atoms.

Conclusions

Publications● P. Tereshchuk, R.L.H. Freire, C.G. Ungureanu, Y. Seminovski, A. Kiejna, J.L.F. Da Silva, Phys. Chem. Chem. Phys. (2015) DOI: 10.1039/C4CP06016D

● A.S. Chaves, G.G. Rondina, M.J. Piotrowski, J.L.F. Da Silva, Computational Materials Science 98 (2015) 278.

● P. Tereshchuk, M.J.Piotrowski, J.L.F. Da Silva, RSC Advances 5 (2015) 521.

● F.P. Sabino, L.N. de Oliveira, J.L.F. Da Silva, Physical Review B 90 (15) (2014) 155206.

● A.S. Chaves, G.G. Rondina, M.J. Piotrowski, P. Tereshchuk, J.L.F. Da Silva, The Journal of Physical Chemistry A 118 (2014) 10813.

● M.J. Piotrowski, P. Tereshchuk, J.L.F. Da Silva, The Journal of Physical Chemistry C 118 (2014) 21438.

● R.L.H. Freire, A. Kiejna, J.L.F. Da Silva, The Journal of Physical Chemistry C 118 (2014) 19051.

● P. Tereshchuk, A.S. Chaves, J.L.F. Da Silva, The Journal of Physical Chemistry C 118 (2014) 15251.

● P. Tereshchuk, R.L.H. Freire, J.L.F. Da Silva, RSC Advances 4 (2014) 9247.

using local, LCCA, and blue-gene resources

Thank you!

from 2014 and up to now 9 publications