Fast approximate methods for global chemical insight DFTB

Computational Chemistry: time & length scales time (s) continuum methods COSMO-RS (My) 1012 …… (s) mesoscale methods 100 molecular dynamics kinetic Monte Carlo Reax. FF (ms) 10 -3 (ms) 10 -6 (ns) 10 -9 (ps) 10 -12 (fs) 10 -15 semi-empirical DFTB ab initio DFT length (m) (nm) 10 -9 (mm) 10 -6 (mm) 10 -3 (m) 100 Copyright © 2012, SCM. ADF seminar UD, 23 March 2012 (AU) 109

Density-functional Based Tight-Binding (DFTB) Fast and efficient approximated DFT: ideally suited for large systems Precomputed pairwise Hamiltonian/Overlap Molecular System H S Charges/Energy / Orbitals Copyright © 2012, SCM. • from DFT calcs. • includes vd. W, relativistic • need for each A-B pair • highly transferable • tedious work – automate QUASINANO project SCM – Heine group ADF seminar UD, 23 March 2012

DFTB: current capabilities • • • Second-order or third-order self-consistent charges (SCC, DFTB 3) Molecules, polymers, surfaces, bulk Geometry and transition state optimization Frequencies, phonons, (P)DOS, band structure, Mulliken analysis Molecular Dynamics: velocity Verlet, Scaling or Berendsen thermostat Fully integrated in GUI (pre-optimization/Hessian re-use ADF/BAND) Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

DFTB - tensile simulations of Mo. S 2 nanotubes Harmonic behaviour until rupture! I. Kaplan-Ashiri, S. R. Cohen, K. Gartsman, R. Rosentsveig, V. Ivanovskaya, T. Heine, G. Seifert, H. D. Wagner, and R. Tenne, Proc. Natl. Acad. Sci. USA 103 (2006), 523 -528. Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

QUASINANO (EU project), DFTB: outlook • Automated ADF + BAND parameter generation for DFTB • Future work (2 years): • Parametrization for large part of periodic table • Properties (reuse ADF code. . ) • Hybrid DFT / DFTB method (nontrivial) COF-5 COF B. Lukose, A. Kuc, T. Heine, Chemistry Eur. J. 2011, 17, 2388 -2392; B. Lukose, A. Kuc, J. Frenzel, T. Heine, Beilstein J. Nanotechnology 2010, 1, 60 -70. Broad applicability depends on (automatic) generation of reliable DFTB parameters for large part of periodic table Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Other fast approximate methods with our GUI • • MOPAC 2009: Stewart’s semi-empirical PM 3, PM 6 -DH, … • molecules, periodic systems (gamma point only) • 70 atoms parametrized (up to Bi, but no lanthanides) UFF: Universal Force Field: all elements; molecules & periodic Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

COSMO-RS Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

COSMO-RS (COnductor-like Screening Model for Realistic Solvents) • • Quantum-based (post-SCF) thermodynamic properties liquids Original: Dr. Klamt (J. Phys. Chem. A 102 (1998) 5074; book) ADF: reparametrized by Pye, Ziegler, van Lenthe, Louwen • 216 molecules against 642 exp. data: • vapor p: ~0. 2 log, partition coeff. : ~0. 35 log, hydration ~0. 37 kcal/mol Instantaneous prediction of thermodynamic properties of mixed liquids: • activity coefficients, solvent free energies • excess energies for mixing GE, HE, TSE • boiling points, solubilities, partition coefficients, vapor-liquid equilibria • p. Ka Database of 1892 precalculated molecules, including many solvents Easy to calculate more compounds with ADF Database and COSMO-RS GUI included in license Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

COSMO-RS Conductor-like Screening Model for Real Solvents Calculation of the chemical potential -profile: charge density on COSMO ( = ) surface pair-wise interaction between molecules statistical thermodynamics October 2010 Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Solvation energies, activity coefficients, solubility Water is the solvent Experimental values taken from: • • • A. Klamt et al. , J. Phys. Chem. A 102 (1998) 5074 J. Li et al. , Analytical Chemistry 65 (1993), 3212 Wikipedia Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

p. Ka values (acid) AH (aq) + H 2 O (l) → H 3 O+ (aq) + A- (aq) (base) BH+ (aq) + H 2 O (l) → H 3 O+ (aq) + B (aq) Empirical fitting as in [1], different parameters used for ADF COSMO-RS Fitting calculated Δgdiss against experimental p. Ka (acid) p. Ka = 0. 62 ΔGdiss/(RT ln(10)) + 2. 10 (base) p. Ka = 0. 67 ΔGdiss/(RT ln(10)) - 2. 00 Experimental values taken from [1] F. Eckert, M. Diedenhofen, A. Klamt, Mol. Phys. 108 (2010) 229 Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Vapor pressure ternary mixture Methanol, Acetone. Chloroform at 330 K Copyright © 2012, SCM.

Reax. FF Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Engineering challenges…. Coal power plant - Higher efficiency - Lower exhaust - Higher combustion temperature - Need new materials that can sustain higher temperatures and oxidation chemistry Pre-oxidized Al-tube with ethylene/O 2/ozone mixture - Higher efficiency - Longer lifetime - Cheaper - Need new, cheap catalyst materials that are resistant to Ni-particle reacting with propene poisoning at T=1500 K Fuel cell …require atomistic-scale solutions

Reax. FF Computational expense 1000000 Time/iteration (seconds) 100000 10000 x 1000, 000 100 QM (DFT) Reax. FF 10 1 0. 01 0 100 200 300 Nr. of atoms 400 -Reax. FF allows for reactive MDsimulations on systems containing more than 1000 atoms - Reax. FF is 10 -50 times slower than nonreactive force fields - Better scaling than QM-methods (Nlog. N for Reax. FF, N 3 (at best) for QM

Failure of the harmonic model Energy (kcal/mol) C-C bond stretching in Ethane Around the equilibrium bond length Full dissociation curve C-C bond length (Å) -Reax. FF employs a bond length/bond order relationship -All connectivty-dependent-parameters bond-length dependent

Reax. FF in ADF - collaboration van Duin • Improved usability • Geometry builder • Input set up, output visualization • Speed: • Serial speed-ups • parallelized version • removed memory bottlenecks (now 100, 000 atoms on laptop) • Combinations with ADF: • Transition State search using ADF’s algorithms • Also geometry optimization, numerical frequencies, . . • Future: QM/MM? Not trivial Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Reax. FF integration into graphical user interface Collaboration van Duin group - SCM Integration team: Olivier Visser, Alexei Yakovlev (SCM) - Mike Russo, Kaushik Joshi (Penn State) Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Reax. FF: Reactions in large, dynamical systems not currently described by Reax. FF YSZ/Ni/butane interface simulation at T=750 K Large part of periodic table covered, including metals Enables dynamics studies of reactions in material science Adri van Duin, Goddard, and coworkers

Reax. FF parameter files • Standard force field parametrizations in ADF 2012: • • • (H/O/N/B) Ammonia Borane Al-water: (AL/H/O) - unpublished Au. O: (Au/O) CHO: (C/H/O) Hydrocarbon oxidation Cu-water: (Cu/H/O) Fe. OCH: (Fe/O/C/H) HE: (C/H/O/N) RDX/High Energy Na. H: (Na/H) Ni. CH: (Ni/C/H/O/N/S/F/Pt/Cl) VOCH: (V/O/C/H) Zn. OH: (Zn/O/H) • Additional standard force fields to follow gradually • Tools to make new parametrization available in the code, BUT currently too hard for non-expert • Semi-automated approach using Genetic Algorithms (ADF 2013? ) Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Aqueous phase reactions and surface chemistry MD(300 K) With Kim & Kubicki (PSU) Zn. O/H 2 O Partially hydroxyl covered surface Water/Ti. O 2 5 Si(OH)4+OH- Si 5 O 15 H 9+6 H 2 O Zeolite growth With Thuat Trinh (Eindhoven) Cu/Zn oxides With Raymand & Hermannsson (Uppsala) Reax. FF for water Dendrimers/metal cations Pt/Ni fuel cells Nafion fuel cell Enzymes/ Proteins DNA/ With Ramie & Doren(Delaware) organic Phosphates/sulfonates Jahn-Teller distorted With Ram Devanathan (PNNL)) catalysis Cu(H O) 2+-cluster

Examples of recent parallel Reax. FF simulations Hexane cracking on a Fe/H-ZSM 5 catalyst (Fe/O: Aryanpour et al. , JPC-A 2010) Noble gas accommodation coefficients on a graphene wafer (Kamat et al. , submitted) Copyright © 2012, SCM. Cu-metal particle on a Zn. O-support with water vapor (Zn/O: Raymand et al. , Surf. Sci. 2010) Pyrolysis of an Illinois coal sample (Kamat, Russo, Mathews and van Duin, in print) ADF seminar UD, 23 March 2012

Summary • DFT: accurate, static calcs of <1000 atoms • Semi-empirical programs (DFTB/MOPAC) for large approximate calculations of molecules & periodic systems • COSMO-RS for thermodynamic properties fluids/mixtures • Reax. FF for large-scale reactive molecular dynamics • Reax. FF, DFTB limited by parameters • Work in progress to automate • (Advanced MD / QM/MM) • Future: workflow to automate complex job set-ups Copyright © 2012, SCM. ADF seminar UD, 23 March 2012

Thank you! Questions? http: //www. scm. com/News/Research. Highlights E-mail: goumans@scm. com Copyright © 2012,

New python tool: Py. MD Adaptive QM/MM Metadynamics T-region R 2 t=∆ R 1 t=2∆ E-region A-region Smooth QM MM transition molecules passing the QM/MM boundary. Copyright © 2012, SCM. t=N∆ ADF seminar UD, 23 March 2012

DFTB features (April 2011) - DFTB with Self Consistent Charge (SCC) London Dispersion correction for vd. Waals interactions Single Point, Geometry Optimization, Transition State Optimization Vibrational Frequencies, Molecular Dynamics non-Periodic and Periodic systems, with multiple k-points Optimization of geometry and/or lattice parameters Molecular Dynamics with Simple Scaling and Berendsen Thermostats Support for restarting in MD simulations Interfaced with ADF-GUI (input set up, visualization results) Copyright © 2012, SCM. ADF seminar UD, 23 March 2012