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A Database of New Zeolite-Like Materials

A Database of New Zeolite-Like Materials. Michael W. Deem Rice University. TexPoint fonts used in EMF: A A A A A A A A A A A A. Outline. Motivation Monte Carlo sampling to construct database History of database of hypotheticals

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A Database of New Zeolite-Like Materials

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

  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. C113 (2009) 21353-21360. R. Pophale, P. A. Cheeseman, and M. W. Deem, Phys. Chem. Chem. Phys. (2011) doi:10.1039/c0cp02255a.

  3. Motivation & Goals • Create database of hypothetical zeolite (SiO2) 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!) LTL EMT VFI

  4. What is a Zeolite? • SiO2 structure • Four-connected network • 3D periodic • 190 known zeolites (Si1-xAlxO2) • Used for • Catalysis, especially petroleum refining • Gas separation • Ion exchange LTL EMT VFI

  5. How Many Space Groups are There? http://cst-www.nrl.navy.mil/lattice/spcgrp/index.html

  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/1000Å3, d = 2 • Loop through 1 ≤ nunique ≤ 8; nunique ≤ 4.5 ntot / nsymm • 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) Euc

  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 LTL EMT VFI

  11. History of Database • Roughly 2000 structures in 1992 JACS114 (1992) 7189-7198 • Compared to a few hundred in Joe V. Smith database • Produced from unit cells of known structures • Reproduced in 2003 J. Phys. Chem. B107 (2003) 8612-8620 • New search begun in 2004 • Geometrical and topological features investigated Ind. Eng. Chem. Res.45 (2006) 5449-5454 J. Phys. Chem. C113 (2009) 21353-21360 Phys. Chem. Chem. Phys. (2011) doi:10.1039/c0cp02255a • Zefsa: http://www.mwdeem.rice.edu/zefsaII

  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 • 6th 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 www.hypotheticalzeolites.net (an excellent website) • 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 www.hypotheticalzeolites.net • 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 • www.hypotheticalzeolites.net/DATABASE/DEEM/

  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. Energetic Refinement Procedure • 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 Add O Energy minimize

  20. Refined Results • Roughly 4 370 000 structures • 3.3M unique Si-only structures • 2.6M unique SiO2 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

  21. Interatomic Potential Anomaly • SLC and BKS force fields contain an anomaly: u=ae-br –c/r6 • 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.

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

  23. 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, 330 000 SLC topologies have been found in this range (or better); 590 000 in BKS subset Framework Energies of Quartz and Known Zeolites From Foster et al., Nature Materials 3 (2004) 234

  24. Energy-Density Distributions • Two major clusters of zeolite-like materials • One group around 18 Si / 1000 A3 • One group around 8 Si / 1000 A3 BKS SLC

  25. Energy-Density Distributions • SLC and BKS structures have similar distributions • The group around 8 Si / 1000 A3 is novel • Corma has made structures in this range: PNAS107 (2010) 13997; Nature458 (2009) 1154. BKS SLC

  26. 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) 1040-1047 • Can the rest of the distribution be made? • Can the low-density structures (8 Si / 1000 A3) be made? SLC BKS

  27. 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 SLC BKS

  28. 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 SLC BKS Knowns

  29. 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

  30. High-Frequency Dielectric Constant • Example property calculation • Many structures with desirable k < 1.6 Angew. Chem. Int. Ed.45 (2006) 6329-6332 • Large rings correlated with low k

  31. 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 DiffractionS23 (2008) 5-12 SLC BKS Knowns

  32. Screening the Database • David Sholl at Georgia Tech • Adsorption, diffusion, geometry • Berend Smit at Berkeley • CO2 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”

  33. Big Picture Questions/Challenges • Can we identify structures for particular applications? • e.g. CO2separation? • 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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