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Connecting Experiment and Theory across Length and Time-scales Algorithms and Software for Materials Research C yber I

Connecting Experiment and Theory across Length and Time-scales Algorithms and Software for Materials Research C yber I nfrastructure. J. J. Rehr Department of Physics University of Washington Seattle, WA. Why we need computational theory: ``If I can’t calculate it,

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Connecting Experiment and Theory across Length and Time-scales Algorithms and Software for Materials Research C yber I

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  1. Connecting Experiment and Theory across Length and Time-scales Algorithms and Software for MaterialsResearchCyberInfrastructure J. J. Rehr Department of Physics University of Washington Seattle, WA

  2. Why we need computational theory: ``If I can’t calculate it, I don’t understand it.” R.P. Feynman

  3. What’s going on outside NSF in CIfor computational materials research?

  4. CI at the DOE CMSN Synchrotron x-ray sources Advanced Computation Currently five CRTs linking scientists at Universities, National Laboratories and Industry

  5. CI in Europe European Theoretical Spectroscopy Facility nanoquanta Psi_k WIEN2k, VASP, ABINIT, ADF, …

  6. Example 1: Multiple frequency scales:X-rayAbsorption Spectra (XAS) theory vs expt fcc Al arXiv:cond-mat/0601242 http://leonardo.phys.washington.edu/feff/opcons UV X-ray Photon energy (eV)

  7. CI:New Theory/Algorithm development:Green’s FunctionCodes ● Beyond Ground State Density Functional Theory and Quasiparticles ● Inelastic losses, self-energy Σ, vibrations, … ● Core-hole effects Σ +

  8. Paradigm shift: Use Green’s functionsnotwave functions! Ψ Efficient!

  9. FEFF8 USER FRIENDLY ab initio XAS Code Matrix inversion 89 atom cluster BN Core-hole, SCF potentials Essential!

  10. FAST Parallel Computing Algorithms FEFFMPI MPI: Natural parallelization G(E) Each CPU does few energies Lanczos: Iterative matrix inverse Smooth crossover between XANES and EXAFS! 1/NCPU

  11. Impact: Quantitative Theory of XAS; Quantitative Analysis of EXAFS and XANES 1000’s of applications J. J. Rehr & R.C. Albers Rev. Mod. Phys. 72, 621 (2000)

  12. Impact on Science:QuantitativeTheory ofOptical ResponseUV – X-ray Dielectric function Energy Loss (EELS) Absorption coefficient Refractive index Reflectivity X-ray scattering factorsf = f0 +f1 +if2 Full spectrumGreen’s function(FEFF8MPI) codes

  13. CI: Bayesian Fit to Experiment J. Synchrotron Rad. 12,70 (2004) Combined fit of XAFS+XANES w/ a priori information Approach: Minimize χ2=Σi|μi theory(X)-μi expt|2 +xAx(a priori information) → [Q + A] x = b Q information matrix A a priori matrix b normalized signal x parameters R,N,… μ0 Natural separation into Relevant (Q dominates) or Irrelevant (A dominates) parameters

  14. Example 2: Multiple length/time scales Real time approach for non-linear optical response in nano-scale systemsPhotonics Devices Y. Takimoto, F. Vila, and J. J. Rehr Supported by NSF Science and Technology Center at UW Grant DMR-0120967 (Y.T. and F.V) and DOE Grant DE-FG02-97ER45623 (JJR) and facilitated by the DOE CMSN.

  15. CI: Real Time-TDDFT for Nano-scale systems* Real space/real timesolution toKohn-Sham equations Perturbation ΔH(t) = − E · xθ(-t) *TDDFT extension of SIESTA (LCAO Basis) A.Tsolakidis, D. Sanchez-Portal and R.M. Martin, Phys. Rev. B 235416 (2002); extended by Y. Takimoto et al.

  16. Static Limit

  17. Optical absorption of FTC chromophores from RT-TDDFT vs experiment FTC(A) FTC(B) FTC(C) Expt: L. Dalton et al. (UW)

  18. CI: New Algorithms for Frequency Dependent Nonlinear responseof large organic photonic chromophores Response function Re B333(ω)is related to the imaginary part of the first-order non-linear polarizability β333. Nonlinear response of FTC chromophore

  19. CI Computer-science Nuts and Bolts forCombined, user-friendlycodes • NEED: standard Input/Output protocols e.g. XML I/O new international standard (SIESTA, ABINIT, chemistry CPL …) • Graphical User Interfaces GUIs e.g. JAVA, PERL or XML based: XFORM – XHTML • International cooperation (e.g. EU: nanoquanta, CML)

  20. (Yoshi Takimoto, UW) xmu.xml in Excel FEFFML –prototypeXML for FEFF schema for FEFF output xmu.dat <feffOutput> <data> <energy>8985.121</energy> <energyWrtEdge>-3.348</energyWrtEdge> <k>0</k> <mu>3.19E-01</mu> <mu0>4.51E-01</mu0> <chi>-1.53E-01</chi> </data> <data> <energy>8985.131</energy> <energyWrtEdge>-3.339</energyWrtEdge> <k>0.05</k>

  21. CI: GUI Development in FEFF (JAVA) (J. Kas UW)

  22. Rx CI for MR Theory • Develop user-friendly codes for materials research Combined ground state, excited state, & analysis codes Condensed matter toolkit • Develop Quantitative understanding of excited states Linking theory and experiment across length & time scales Quantitative Interpretation of Spectra • Trainhigh-performance-computation savvy grad students and postdocs

  23. That’s all folks!

  24. CMSN-ESESRF

  25. ETSF

  26. Inelastic losses Ab initioInelastic Mean Free Path Ab initioCollision Stopping Power λ[ ε(ω) ] CSP [ ε(ω) ] FEFF8-MP FEFF8-MP arXiv:cond-mat/0605135 Application: New Detector Design (PNNL - DHS)

  27. http://www.leonardo.washington.edu/feff/opcons Optical Constants FEFF8 vs DESY Tables

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