Motivation Localisation at Low Temperatures Localisation in Super uid Helium Interaction Induced Localisation of Protons Temperature and Super uid Helium Solvation Effects ukasz Walewski Ruhr-University Bochum VI Workshop in Electronvolt Neutron Spectroscopy, Abingdon 2014 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 1 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Motivation – Super uid Helium Environment Helium Nano Droplet Isolation (HENDI) Spectroscopy1 Ultra-cold & Ultra-gentle Matrix adapts perfectly to the solute → QM ground state delocalisation transparent from IR to UV → refractive index close to 1 spectral line half-width < 0.25 cm−1 → ultra-cold, weak interactions absorbs binding energy → evaporative cooling almost free rotation of the solute → zero viscosity 1 Review: J. P. Toennies, A. F. Vilesov, Angew. Chem. Int. Ed. 43 (2004) 2622 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 2 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Motivation – What Could Be In uenced ? Nuclear Quantum Effects Quantum mechanical treatment of the atomic nuclei, as opposed to the classical point particle viewpoint, affects: molecular structure nuclear delocalisation reactivity. . . Nuclear quantum effects will be investigated for the rst time at super uid helium temperatures. Interaction Induced Localisation of Protons classical nuclei quantum nuclei . W., H. Forbert, D. Marx, J. Phys. Chem. Lett. 2 (2011) 3069 Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 3 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Motivation – What Could Be In uenced ? Nuclear Quantum Effects 8 P(δ) Quantum mechanical treatment of the atomic nuclei, as opposed to the classical point particle viewpoint, affects: 6 4 molecular structure 2 nuclear delocalisation 0 reactivity. . . Realistic description of the electronic structure is necessary. Interaction Induced Localisation of Protons quantum classical T = 100 K −0.4 −0.2 0 0.2 0.4 δ[Å] . W., H. Forbert, D. Marx, ChemPhysChem 14 (2013) 817 Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 4 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Motivation – What Are We Speci cally Interested In ? Aggregation induced chemical reactions 1 00 successive aggregation of H2 O molecules + -1 Energy (kJ mol ) Energy (kJ/mol) -20 −20 + -40 −40 -60 −60 essentially barrierless process + -80 −80 formation of the partially aggregated (PA) structure PA -100 −100 -120 −120 -140 −140 -160 SIP Cooling in He Droplet 10 20 20 00 10 30 40 50 60 70 80 90 HCl dissociation 100 110 120 130 140 150 160 170 180 Simulation Steps/1000 Simulation Steps/1000 this mechanism can not be accessed by exploring the PES of a xed number of H2 O's 1 H. Forbert, M. Masia, A. Kaczmarek, N. N. Nair and D. Marx, JACS 133 (2011) 4062 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 5 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Ultra-Low Temperatures vs Interatomic Interactions T = 1.67 K Reff [ Å ] L H 2.68 1.00 Effective radius of a bound nucleus s √ 3 3 Z Reff = 3 d3~r 4π Ω H2 1.97 0.73 Ω ≡ ∀~r : P(~r) ≥ Pmax · e− 2 H2 O 1.26 0.47 1 Free atom radius of gyration p h2 /2πm kB T Λ free √ = Rg = √ 8π 8π Localisation index HCl 1.26 0.47 L = Reff /Rfree g . W., H. Forbert, D. Marx, Mol. Phys. 111 (2013) 2555 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 6 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Strikingly Strong Localisation Due to Hydrogen Bonds T = 1.67 K Interaction Induced Localisation of Protons Nucleus Cl(1) O(2) O(3) O(4) O(5) H(6) H(7) H(8) H(9) H(10) H(11) H(12) H(13) H(14) Reff [ Å ] 0.31 0.31 0.34 0.37 0.40 0.30 0.41 0.31 0.36 0.37 0.35 0.48 0.66 0.67 L 0.69 0.45 0.50 0.55 0.59 0.11 0.15 0.12 0.13 0.14 0.13 0.18 0.25 0.25 Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 7 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Strikingly Strong Localisation Due to Hydrogen Bonds Cl H T = 1.67 K Effective size of H smaller than that of Cl ? Interaction Induced Localisation of Protons Nucleus Cl(1) O(2) O(3) O(4) O(5) H(6) H(7) H(8) H(9) H(10) H(11) H(12) H(13) H(14) Reff [ Å ] 0.31 0.31 0.34 0.37 0.40 0.30 0.41 0.31 0.36 0.37 0.35 0.48 0.66 0.67 L 0.69 0.45 0.50 0.55 0.59 0.11 0.15 0.12 0.13 0.14 0.13 0.18 0.25 0.25 Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 8 Motivation Localisation at Low Temperatures Localisation in Super uid Helium H2 O· · · HOH P ( Rg / Rgfree H ) Interaction-Induced Localisation 1.67 K 12 O H 6 0 107 K 12 6 H2 O· · · HCl P ( Rg / Rgfree H ) 0 0 0.5 Rg / Rgfree H 1 1.67 K 12 Cl H 6 0 107 K 12 6 0 0 0.5 Rg / Rgfree H 1 . W., H. Forbert, D. Marx, Mol. Phys. 111 (2013) 2555 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 9 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Interaction-Induced Localisation T Reff (Cl) Reff (H) 1.67 K 0.31 Å 0.30 Å 100 K 0.06 Å 0.22 Å . W., H. Forbert, D. Marx, J. Chem. Phys., in revision Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 10 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Simulating Pure Super uid Helium Indistinguishable identical particles → Bose–Einstein statistics Z D E 1X ˆ ˆ −β H ZBE = Trsym e = dR R e−β H PR N! P T = 3.33 K T = 2.11 K T = 1.18 K Review: D. M. Ceperley, Rev. Mod. Phys. 67 (1995) 279 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 11 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Simulating Pure Super uid Helium Indistinguishable identical particles → Bose–Einstein statistics Z D E 1X ˆ ˆ −β H ZBE = Trsym e = dR R e−β H PR N! P 1.0 0.8 3.0 ρs / ρ Cv 4.0 2.0 1.0 0.6 0.4 0.2 1 2.17 T[K] 3 1 2.17 3 T[K] T = 2.11 K Review: D. M. Ceperley, Rev. Mod. Phys. 67 (1995) 279 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 12 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Simulating Molecules in Super uid Helium – A Hybrid Method Hybrid Interactions (à la QM/MM) solute: Born-Oppenheimer energy of the ground electronic state (QM) solvent: effective He–He pair potential (MM) solute–solvent: parameterized interaction potential 1 tted using highly accurate SAPT and CC data accounts for different solute con gurations 1 A. D. Boese, H. Forbert, M. Masia, A. Tekin, D. Marx, G. Jansen PCCP, 13 (2011) 14550 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 13 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Simulating Molecules in Super uid Helium – A Hybrid Method1 Hybrid Sampling (MD/MC) solute: ab initio PIMD solvent: bosonic PIMC ˆ ˆ ˆ e−β (HBO +HHe−He +Hinter ) Correct sampling of the canonical density matrix for the total system → Implemented in our in house CP2K version 1 . W., H. Forbert, D. Marx, Comp. Phys. Comm., doi: 10.1016/j.cpc.2013.12.011 Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 14 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Additional Localisation Due to Super uid Helium? Lgp LHe 0.8 L 0.6 0.4 0.2 δL 0.2 1 3 5 7 9 11 Atom Index 13 Relative effect on the order of 10-20% . W., H. Forbert, D. Marx, J. Chem. Phys., in revision Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 15 Motivation Localisation at Low Temperatures Localisation in Super uid Helium ∆L = Lgp − LHe Additional Localisation Due to Super uid Helium 0.10 0.05 0.00 0 0.25 H, 0.5 Lgp O, 0.75 1 Cl The weaker localisation in GP, the stronger the He effect . W., H. Forbert, D. Marx, J. Chem. Phys., in revision Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 16 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Next Step: Cryochemical Reactions Acid Dissociation Mechanism HCl + 4 H2 O → Cl− + H3 O+ + 3 H2 O approach of an H2 O towards HCl O−H· · · Cl hydrogen bond creation PA SIP HCl dissociation → proton transfer H3 O+ formation → proton transfer δ[Å] 0.4 0.2 0.0 −0.2 T = 1.67 K + 4 He solvation 0 1 2 3 4 5 6 t [ ps ] . W., H. Forbert, D. Marx, Comp. Phys. Comm., and in preparation Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 17 Motivation Localisation at Low Temperatures Localisation in Super uid Helium Acknowledgements People Dominik Marx, RUB Harald Forbert, RUB Georg Jansen, UDE Daniel Boese, UDE Software & Resources CP2K Team LiDOng@Uni-Dortmund CHEOPS@Uni-Köln BoViLab@RUB Funds Interaction Induced Localisation of Protons Electronvolt Neutron Spectroscopy, Abingdon 2014 | . Walewski 18
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