Nanotech2010 High Throughput

Materials discovery with ab initio high throughput calculations

G. Fitzgerald, G. Goldbeck

A. Perlov, Accelrys Software Inc

M. Sarwar, S. French, S. Garçia, A. MartinezM. Sarwar, S. French, S. Garçia, A. Martinez

D. Thompsett, Johnson Matthey

TechConnect WORLD Conference, June 2010, Anaheim, CA

Materials discovery with ab initio high throughput calculations

G. Fitzgerald, G. Goldbeck-Wood, J.L. Gavartin,

A. Perlov, Accelrys Software Inc

M. Sarwar, S. French, S. Garçia, A. Martinez-Bonastre, M. Sarwar, S. French, S. Garçia, A. Martinez-Bonastre,

D. Thompsett, Johnson Matthey

TechConnect WORLD Conference, June 2010, Anaheim, CA

Statement

• Materials discovery typically involves exploration of very large phase space.

• Quantum and atomistic simulation technology are

sufficiently mature to be used to screen materials and

come up with lead candidates.

Bulk and surface defects Alloying

Defect decoration Surface segregation

© 2009 Accelrys, Inc.

come up with lead candidates.

• Robust, yet flexible software infrastructures make it feasible to

– Screen materials even with compute-heavy simulation methods.

– Provide a knowledge and decision base for research teams.

Materials Studio

Materials discovery typically involves exploration of very large phase space.

Quantum and atomistic simulation technology are

sufficiently mature to be used to screen materials and

Clustering

Skin formation

2

Robust, yet flexible software infrastructures make it feasible to

heavy simulation methods.

Provide a knowledge and decision base for research teams.

Pipeline Pilot Client

Pipeline Pilot

Web Port

Materials Studio Collection

Fuel Cell Catalyst application

• Market problem: Fuel Cells issues include

– High Cost

– Limited stability

• Technology problems

– Catalytic breakdown of O2 is rate determining

– Catalysis relies on Platinum

– other metals do not to perform well enough.

• R&D problems: Finding alternatives to Pt

– Different alloy combinations


– Different alloy combinations

– Different alloy microstructures

– i.e. Screening thousands of materials

• Modeling problem: High throughput & relevance

– Complex enumeration of periodic structures

– Long calculation times

– Property analysis relevant to experiment

is rate determining

other metals do not to perform well enough.

3

Modeling problem: High throughput & relevance

Complex enumeration of periodic structures

Overall:½O2+H2 �

PEM Fuel Cells


Anode- hydrogen oxidation:

H2 2H+ + 2e-

� H2O+ electricity

4

Cathode- oxygen reduction:

½O2 +2H+ + 2e- H2O

1

1.2

1.4

Cell Potential [V]

Theoretical Cell Voltage [E° = 1.23 V]

Theoretical cell voltage: 1.23V

Actual much less due to various loss processes

Voltage losses in a PEMFC


0

0.2

0.4

0.6

0.8

0 200 400 600 800

Current Density [mA/cm2]

Cell Potential [V]

Cathode Activation

Theoretical Cell Voltage [E° = 1.23 V]

Actual much less due to various loss processes

5

1000 1200 1400

Current Density [mA/cm2]

Cell Resistance

Anode Activation

Mass Transport

Cell Performance

Adsorption of O2 Dissociation of O

Dissociative ORR mechanism in PEMFC


e-

Combination with a second proton +e

….to form OH

e-

Dissociation of O2 Combination with a proton +e-….

Dissociative ORR mechanism in PEMFC

6

Combination with a second proton +e-….

….to form H2O

Ideal Catalyst – Sabatier’s Principle

• The optimum catalyst-adsorbate interaction must

– Not be too weak:

• Chemical bonds between surface and adsorbate can be formed

• Internal bonds weakened so intermediates can be generated

– Not be too strong

• Intermediates generated can react further

• Desorbtion takes place and freeing up of adsorption sites

• Pt is close to optimum, but expensive


Catalytic

Activity

• Pt is close to optimum, but expensive

– Other pure metals perform worse

– What about alloys?

Sabatier’s Principle

adsorbate interaction must

Chemical bonds between surface and adsorbate can be formed

Internal bonds weakened so intermediates can be generated

Intermediates generated can react further

Desorbtion takes place and freeing up of adsorption sites

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Metal-adsorbate bond strength

Pt

Phase Space

Activity


With high throughput modeling,that would otherwise not be covered

0% - Pt 50% - Pt100% - Co 50% - Co

Phase Space

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modeling, phase space to be exploredcovered experimentally.

100% - Pt0% - Co

Sampling must include structure and composition

Bulk and surface defects Alloying


Defect decoration Surface segregation

Sampling must include structure and composition

Alloying Clustering

9

Surface segregation Skin formation

…

Overview of approach

• Objective: find alloy with similar profile as Pt, slightly weaker bonding

• Generate representative catalyst surface models

• Calculate key properties and determine descriptors of ORR

activity and bonding:

– Material Stability (Segregation Energies)


– Material Stability (Segregation Energies)

– O adsorption Energies

– OH adsorption Energies

– d-band centres

– electronic workfunction

– thermodynamics of reaction steps

• Methodology:

– Plane Wave Density Functional Theory – CASTEP

– High throughput strategies, automation

– Data accumulation and storage in database

– Data Management and reporting

Catalytic

Activity

Metal-adsorbate bond strength

Ptfind alloy with similar profile as Pt, slightly weaker bonding

Generate representative catalyst surface models

Calculate key properties and determine descriptors of ORR

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CASTEP

Data accumulation and storage in database

Work function

High throughput calculations: Overview

© 2009 Accelrys, Inc. 11

AxB1-x ensemble generation

Constrained atoms

1st layer `A`

2nd layer `B`

3rd layer `C`

4th layer `D`

A0B2C2D0


A1

A2

A3

A4

B1

B2

B3

B4

C1

C2

C3

C4

D1

D2

D3

D4

0 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0

)!(!

!

kNk

N

k

N

−=

For a given supercell generate all

configurations with k out of N host

sites substituted by X atomsA0B2C2D0

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Define a configuration class by the

number of substitutions in each layer

Apply symmetry transformations

and find degeneracy of irreducible

configurations

Map each structure into a unique

binary string

Example Pt3Co: 6 layers slab setup

N=16, k=4

configurations

133 – non-equivalent configurations (due to symmetry)

Pt not stable on surface of Pt

A0 superclass contains

1820)!416(!4

!16=

−


A0 superclass structures

A0 superclass contains

Class Conf. x gi Class Conf. x gi Class

A0B4C0D0 1x1 A0B3C1D0 1x12+1x4 A0B2C2D0

A0B3C0D1 1x12+1x4 A0B2C1D1

A0B2C0D2

configurations

equivalent configurations (due to symmetry)

Pt not stable on surface of Pt3Co -> only consider A0 superclass

A0 superclass contains 42 irreducible configurations

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A0 superclass structures

A0 superclass contains 42 irreducible configurations

Conf. x gi Class Conf. x gi Class Conf. x gi

2x6+1x24 A0B1C3D0 1x4+1x12 A0B0C4D0 1x1

4x12+2x24 A0B1C2D1 4x12+2x24 A0B0C3D1 1x12+1x4

2x6+1x24 A0B1C1D2 4x12+2x24 A0B0C2D2 2x6+1x24

A0B1C0D3 1x12+1x4 A0B0C1D3 1x12+1x4

A0B0C0D4 1x1

Pt3Co: most stable configurations


E = E0

ba

E = E0 + 0.03 eV E = E0+ 0.04 eV

~11 configurations give significant contribution into the TD average.

Entropic factor may be important

999.0

96.0

/)(

11,1

11

/)(

4,1

4

0

0

==

==

−−

=

−−

=

∑

∑TkEE

j

j

TkEE

j

j

Bj

Bj

egZ

egZ

14

c d

E = E0+ 0.04 eV E = E0+0.07 eV

~11 configurations give significant contribution into the TD average.

J. L. Gavartin et al., Transactions of the

Electrochemical Society 25(1) 1335-1344 (2009).

Surface phase diagram

• stoichiometry near the surface may significantly deviate from its nominal bulk value.

Understanding surface phase diagram is critical for

– assessing catalytic reactivity

– testing electrochemical stability

Pd3Co: The thermodynamic Co fraction in the

second and third layers is

Pt Co : The variation of Co fraction between the

thermodynamic fraction fk of metal X in the layer k


Pt3Co : The variation of Co fraction between the

layers is somewhat less pronounced.

Shuo Chen et al Am. Chem. Soc./ 2008, 130, 13818

stoichiometry near the surface may significantly deviate from its nominal bulk value.

Understanding surface phase diagram is critical for

Co: The thermodynamic Co fraction in the

second and third layers is overstoichiometric;

Co : The variation of Co fraction between the

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Co : The variation of Co fraction between the

layers is somewhat less pronounced.

Shuo Chen et al Am. Chem. Soc./ 2008, 130, 13818

Effect of lattice strain on oxygen adsorption

)(2

1)()( 2

* OEsurfaceEsurfaceOEEad −−+=

Compressive lateral strain leads to

approximately linear decrease of the

Oxygen adsorption energy, while lattice

expansion leads to an increase of Eads(O).

A similar trend was reported earlier for

Cu(111), Ru(0001) and Au(111) surfaces.


Cu(111), Ru(0001) and Au(111) surfaces.

Y. Xu, Surf. Sci., 494, 131-144 (2001).

M. Mavrikakis, Phys. Rev. Lett., 81, 2819 (1998).

M. Mavrikakis, Catal. Lett., 64, 101 (2000).

O adsorption on most stable (Pt/Pd)3Co

surfaces suggests some additional efects

besides strain, e.g. chemical modification

and surface relaxation.

Effect of lattice strain on oxygen adsorption

expansion leads to an increase of Eads(O).

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surfaces suggests some additional efects

besides strain, e.g. chemical modification

High throughput materials calculations


Creating the discovery database


Reporting and mining the database


Calculations database: Portal

Access via a Web Portal:

1. Choose the database name (local or remote)

2. Choose composition of a material of interest

3. Choose report tables to show


1. Choose the database name (local or remote)

2. Choose composition of a material of interest

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Calculations database: systems overview

Statistics for all selected jobs: Run time and CPUs used

Systems categorized as bulk, slab or molecule and shown by chemical composition

Choose the chemical composition of interest


Calculations database: systems overview

Statistics for all selected jobs: Run time and CPUs used

and shown by chemical composition

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Calculations database: Table of runs for a system

Sortable tables display key job information (a single calculation per line):

Choose the specific individual calculation to see all its details


Calculations database: Table of runs for a system

Sortable tables display key job information (a single calculation per line):

Choose the specific individual calculation to see all its details

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Calculations database: Job details

The details are given in different tables, that may be shown or hidden

Jmol visualiser for structure viewing, manipulation and analysis


The details are given in different tables, that may be shown or hidden

Jmol visualiser for structure viewing, manipulation and analysis

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Results details: Workfunction and d-band centre


band centre

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Oxygen Reduction Reaction


E

E0=E(O2+*)

ETS=E(O*-O*)

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Reaction coordinate

E1=E(O2*)

E2=2E(O*)

Ediss=E2-E1 Eads1=E1-E0

Ea=ETS-E1 Eads2=E2-E0

Eads1=E1-E0

iCatDesign

Reaction free energy protocol

•Calculate free energy of main steps of dissociative ORR reaction as

a function of cell potential U

On input:

File with energies

Cell Potential U

Substrate

O adsorbed

OH adsorbed


1. J.K. Nørskov, J. Rossmeisel, A. Logadottir, et al.J. Phys. Chem. B,108, 17866

OH adsorbed

H2O and H2 gas phase

Correction energies

(-ST, ZPE, solvation)


Calculate free energy of main steps of dissociative ORR reaction as

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1. J.K. Nørskov, J. Rossmeisel, A. Logadottir, et al.J. Phys. Chem. B,108, 17866-17892 (2004).

Summary

• A series of tools and models have been developed for screening various Pt alloy

combinations for stability and activity.

• Tools developed can be used to screen Pt and non

• ORR activity is improved by lattice strain (compressive for Pt)

• Strain is controlled by alloying with base metals antisegregating away from the

surface (typically metals with smaller atomic radius)

• D-band centre, surface segragation and adsorption energies are found to be useful

descriptors


descriptors

A series of tools and models have been developed for screening various Pt alloy

Tools developed can be used to screen Pt and non-Pt compositions

ORR activity is improved by lattice strain (compressive for Pt)

Strain is controlled by alloying with base metals antisegregating away from the

surface (typically metals with smaller atomic radius)

band centre, surface segragation and adsorption energies are found to be useful

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Conclusions: High Throughput Calculations

• Materials Discovery beyond the trivial case requires a vast number of systems to be studied, each requiring HPC computing itself.

• Successful projects require collaboration of different organizations and modeling with experiment.

• Require new strategies allowing for large multicollaborative projects providing automation in – optimization of calculations – strict quality control


– strict quality control– streamlined analysis and reporting– Data storage and mining in a flexible, extensible database

• Pipeline Pilot and the Materials Studio Collection have been used to– Build a framework for Materials HTC

• Automated job generation, execution and analysis• Datamining via web portal

– Screen >2000 catalyst leads and identify candidates for development– Provide a source for project teams to explore.

Conclusions: High Throughput Calculations

Materials Discovery beyond the trivial case requires a vast number of systems to be studied, each requiring HPC computing itself.

Successful projects require collaboration of different organizations and

Require new strategies allowing for large multi-platform and multi-user collaborative projects providing automation in

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Data storage and mining in a flexible, extensible database

Pipeline Pilot and the Materials Studio Collection have been used toBuild a framework for Materials HTC

Automated job generation, execution and analysis

Screen >2000 catalyst leads and identify candidates for developmentProvide a source for project teams to explore.

Acknowledgements

• Dan Ormsby

• Amity Andersen

• David Gunn

• Arek Krzystala

• Victor Milman

• Patricia Gestoso-Suoto

J. L. Gavartin, M. Sarwar, D. C. Papageorgopoulos, D. Gunn, S. Garcia,

A. Perlov, A. Krzystala, D. L. Ormsby, F. Liu, G. Goldbeck

Andersen, S. French, D. Thompsett. Exploring fuell cell cathode

materials: High throughput calculation approach.

Transactions of the Electrochemical Society


Funding:

This project is partly funded under Technology Strategy Board Project Number:

/5/MAT/6/I/H0379C. The TSB is a business

established by the government. Its mission is to promote and support research into, and

development and exploitation of technology and innovation for the benefit of UK

business, in order to increase economic growth and improve the quality of life. It is

sponsored by the Department for Innovation, Universities and Skills (DIUS) (22).

J. L. Gavartin, M. Sarwar, D. C. Papageorgopoulos, D. Gunn, S. Garcia,

A. Perlov, A. Krzystala, D. L. Ormsby, F. Liu, G. Goldbeck-Wood, A.

Andersen, S. French, D. Thompsett. Exploring fuell cell cathode

materials: High throughput calculation approach.

Transactions of the Electrochemical Society 25(1) 1335-1344 (2009).

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This project is partly funded under Technology Strategy Board Project Number:

/5/MAT/6/I/H0379C. The TSB is a business-led executive non-departmental public body,

established by the government. Its mission is to promote and support research into, and

development and exploitation of technology and innovation for the benefit of UK

business, in order to increase economic growth and improve the quality of life. It is

sponsored by the Department for Innovation, Universities and Skills (DIUS) (22).

Nanotech2010 High Throughput

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