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A Database of New Zeolite-Like Materials Michael W. Deem Rice University TexPoint fonts used in EMF: A A A A AA A A A AAA.

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Presentation on theme: "A Database of New Zeolite-Like Materials Michael W. Deem Rice University TexPoint fonts used in EMF: A A A A AA A A A AAA."— Presentation transcript:

1 A Database of New Zeolite-Like Materials Michael W. Deem Rice University TexPoint fonts used in EMF: A A A A AA A A A AAA

2 Outline Motivation Monte Carlo sampling to construct database History of database of hypotheticals Geometric, topological, and physical properties of the predicted materials Challenges M. W. Deem, R. Pophale, P. A. Cheeseman, and D. J. Earl, J. Phys. Chem. C 113 (2009) R. Pophale, P. A. Cheeseman, and M. W. Deem, Phys. Chem. Chem. Phys. (2011) doi: /c0cp02255a.

3 Motivation & Goals Create database of hypothetical zeolite (SiO 2 ) structures Structures should have favorable framework energies Screen for materials with unique properties to identify interesting synthetic targets –Catalysis, sorption, k ∞ Identify synthesis conditions (hard problem!) LTLEMTVFI

4 What is a Zeolite? SiO 2 structure Four-connected network 3D periodic 190 known zeolites (Si 1-x Al x O 2 ) Used for –Catalysis, especially petroleum refining –Gas separation –Ion exchange LTLEMTVFI

5 How Many Space Groups are There?

6 The Search Procedure Loop through space groups Loop through 3  ≤ a,b,c ≤ 30Å, dr=3Å; , ,  d  10° Loop through 12 ≤  ≤ 20 T atoms/1000Å 3, d  = 2 Loop through 1 ≤ n unique ≤ 8; n unique ≤ 4.5 n tot / n symm Run zefsaII 100 times (solves 86% of known structures) Keep structures with E < 0 Keep best example (lowest E/atom) of each unique topology

7 Monte Carlo Procedure For a unit cell with a given space group symmetry, tetrahedral atom density and number of crystallographically unique tetrahedral atoms we want to identify as many reasonable topologies as possible To do this we use (many) simulated annealing Monte Carlo simulations

8 The Figure of Merit Contains geometric and density terms Weighting parameters selected to efficiently solve known zeolite topologies Note only tetrahedral atoms included (no oxygens) E uc

9 Aside: Structure Solution SSZ-77 ZEFSA/ZEFSAII originally developed (and still used) for zeolite structure solution One can also include a match to X-ray powder data in the figure of merit to directly solve structures This approach has been effective in solving the structures of at least a dozen zeolites and other layered structures to date SSZ-77: New high-silica zeolite Structure solution elucidated synthesis conditions –Template decomposed –Decomposition product was the SDA

10 Hypotheticals Database Create database of hypothetical structures Thermodynamically accessible Mine for structures with unique properties Identify synthesis conditions to make LTLEMTVFI

11 History of Database Roughly 2000 structures in 1992 JACS 114 (1992) Compared to a few hundred in Joe V. Smith database Produced from unit cells of known structures Reproduced in 2003 J. Phys. Chem. B 107 (2003) New search begun in 2004 Geometrical and topological features investigated Ind. Eng. Chem. Res. 45 (2006) J. Phys. Chem. C 113 (2009) Phys. Chem. Chem. Phys. (2011) doi: /c0cp02255a Zefsa:

12 Using the NSF TeraGrid Method is perfect for scavenging idle CPU time For a typical desktop processor, 1 simulated annealing run takes on the order of minutes Condor is an efficient implementation of CPU scavenging at Purdue University Over the last 5 years we have scavenged approx. 6 million CPU hours from machines on the NSF TeraGrid

13 NSF TeraGrid Usage 6 th biggest user of TeraGrid in 2006 Largest user at Purdue in 2006 Throughput possibilities – Linux circa 2008/11. Note peaks and valleys...

14 Other Hypothetical Databases See (an excellent website)www.hypotheticalzeolites.net Hosts the Foster/Treacy database Provides links to our database, Bell/Klinowski hypotheticals, Predicted Crystallographically Open Database, Reticular Chemistry Structure Resource, Euclidean Patterns in Non-Euclidean Tilings, Jilin University

15 Forster/Treacy Database We are very grateful to Martin Forster and Michael Treacy for hosting our database on Forster/Treacy Database –933K GULP refined structures (silver) –333 gold structures –Statistics About 3x duplicates in silver database Of non-duplicates, about 5% within +0.1 eV/Si on BGB forcefield (≈ +60 kJ/Si Jackson/Catlow forcefield) About 30% of these are within +30 kJ/Si of quartz Thus, about 5,700 structures in silver database within +30 kJ/Si Earl/Deem database –4.4M unique structures –2.6M refined with GULP –1.4M within +60 kJ on SLC interatomic potential –330K within +30 kJ on SLC interatomic potential

16 Search Capability Plan Organize and analyze database –Density –Pore size –Ring distribution –Coordination sequence –PXD (Le Bail’s PCOD and P2D2) –icdd, icsd, MDI-JADE, CrystalMatch commercial databases

17 Viewing the Database

18 Si-Only Results 4.37 million structures found As the structures produced by our Monte Carlo annealing procedure are energetically favorable, many have good framework energies

19 Coverage of Hypotheticals 86% of known structures solved

20 Add O atoms between all T atoms that are connected (recall that only T atoms are included in initial sweep of crystallographic space) Use an atomistic force-field (Jackson & Catlow, 1988) and energy minimize the structure using a Newton-Raphson procedure in the GULP program Energetic Refinement Procedure Add O Energy minimize

21 Refined Results Roughly structures 3.3M unique Si-only structures 2.6M unique SiO 2 structures Two interatomic potentials used –Polarizable SLC –Non-polarizable BKS Thermodynamically accessibility –SLC: 330k structures within +30 kJ/mol Si –BKS: 590k structures within +65 kJ/mol Si

22 Interatomic Potential Anomaly SLC and BKS force fields contain an anomaly: u=ae -br –c/r 6 –Overlapping atoms or cores and shells can have negative, infinite energy This will result in structures with poor geometry, but overlapping atoms, to appear to have favorable energies –E.g. structures with energy below α-quartz. This anomaly was fixed by changing the exp-6 potential to extrapolate to a large value at r=0 Largely eliminates “too good” structures with energies below α-quartz.

23 Some Structures From SLC database Structures with energies no greater than 30 kJ/mol Si of α-quartz Typical, zeolite-like structures

24 Framework Energies of Quartz and Known Zeolites Most known zeolites are within 30 kJ / mol Si of the framework energy of quartz in the SLC interatomic potential Of the 4.37 million topologies from the initial search, SLC topologies have been found in this range (or better); in BKS subset From Foster et al., Nature Materials 3 (2004) 234

25 Energy-Density Distributions Two major clusters of zeolite-like materials One group around 18 Si / 1000 A 3 One group around 8 Si / 1000 A 3 SLC BKS

26 Energy-Density Distributions SLC and BKS structures have similar distributions The group around 8 Si / 1000 A 3 is novel Corma has made structures in this range: PNAS 107 (2010) 13997; Nature 458 (2009) SLC BKS

27 Zeolite Synthesis Mechanism Lie at low-density edge of zeolite- like distribution Probably due to current synthetic techniques Mechanistic explanation of feasability factor D. Majda et al. J. Phys. Chem. C 112 (2008) Can the rest of the distribution be made? Can the low-density structures (8 Si / 1000 A 3 ) be made? SLC BKS

28 Ring Distributions Fundamental, non-decomposible rings SLC and BKS topologies are similar Quite a few large-membered rings Distribution not sensitive to presence of 3-rings SLCBKS

29 Ring: Hypotheticals vs Knowns Reasonably good agreement between predicted and known ring distributions SLC and BKS ring distributions are similar More large-membered rings predicted to exist 3-rings correlated with 9-rings in knowns, but not in hypotheticals SLCBKSKnowns

30 Low Energy Structures Structures with energy below quartz –Can be artifacts of overlapping shells or atoms in SLC or BKS In this version of the database there are only 2 within -30kJ/molSi for SLC and none within -65kJ/molSi for BKS

31 High-Frequency Dielectric Constant Example property calculation Many structures with desirable k < 1.6 Angew. Chem. Int. Ed. 45 (2006) Large rings correlated with low k

32 PXD Search/Match Structures deposited in Armel Le Bail’s PCOD and P2D2 Within 1% on cell parameters for knowns So, search/match should succeed A. LeBail Powder Diffraction S23 (2008) 5-12 KnownsBKSSLC

33 Screening the Database David Sholl at Georgia Tech –Adsorption, diffusion, geometry Berend Smit at Berkeley –CO 2 sequestration Chris Floudas at Princeton –Geometry Randy Snurr Northwestern –MOF analogs Catalysis –D. Majda et al., J. Phys. Chem. C, 112 (2008) 1040, “Hypothetical Zeolitic Frameworks: In Search of Potential Heterogeneous Catalysts” –B. Smit & T. L. M. Maesen, Nature, 451 (2008) 671, “Towards a molecular understanding of shape selectivity”

34 Big Picture Questions/Challenges Can we identify structures for particular applications? –e.g. CO 2 separation? How does one synthesize them? –Which structures can be synthesized? –What OSDAs can be used to make them? Also: solution conditions, co-templates Significant reason for promise


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