Interface MD Application

Transcription

1 Interface MD Application July 15, 2017 Hendrik Heinz Department of Chemical and Biological Engineering Materials Science and Engineering Program University of Colorado-Boulder, CO, USA 1

2 Predict Facet-Specific Binding of Peptides in Solution to Surfaces and Nanoparticles (Pd) C D E {111} {110} {100} 5 Å E a = -68±1 E a = -43±2 E a = +3±1 F 5 21 Å G 7 26 Å 9 31 Å H 10 Å E a = -20±1 E a = -17±1 Pd C N O H E a = -29±2 Pd4 peptide = TSNAVHPTLRHL Ramezani-Dakhel et al. 2017, 9,

3 Predict of Activity a of Pd Nanoparticle Catalysts in C-C Coupling Reactions (Stille Reaction) Mechanism Activity a b Rate determining step a a b b Abstraction (kcal/m given particle shape, determined from HE > 8 e Particle shape (Pd4) E i RT b b Abstraction Abstraction energy energy (kcal/mol) (kcal/mol) > 85 R N : total R N : rate total of rate abstraction of abstraction E i : abstraction E i : abstraction energy energy of atom of iatom i N : total N : number total number of surface of surface atoms atoms > 85 c c 1 1 RNR ~ N ~ N N e Catalytic efficiency is predictable for any XRD/PDF data, and using the computed atom leaching rate N Ei R N R: total rate of RT Ee N : total rate of abstraction i : E energy E i of : atom abstract i : abstraction energy of atom i i i 1N : N total : total number number of surface of N surface : atoms atoms H. Ramezani-Dakhel, M. R. Knecht, R. R. Naik, H. Heinz PCCP 2013; ACS Nano 2015, 9, 5082; Chem. Sci. 2015, 6, c N i 1i 1 N Ei Ei RT RT R N e ~ 1 N R N : total rate total num 3

4 Explain Interlayer Structure in Clay Minerals (Alkylammonium-Montmorillonite) Basal plane spacing (A) monolayer complete bilayer complete Carbon atoms per chain NH 3 head group NMe 3 head group (C n H 2n+1 NR 3 ) 0.33 (Si 4 O 8 )[Al 1.67 Mg 0.33 O 4 (OH) 4 ] CEC 90 mmol/100g HRTEM of MMT embedded in an epoxy matrix (Drummy et al. JPCB 2005) Increase of basal-plane spacing in a step-like pattern according to the formation of an alkyl monolayer, alkyl bilayer etc (<5% dev from XRD) Gallery spacing for peralkylated head groups rises smoothly and is shifted by ~ 2 C atoms relative to primary ammonium head groups ( bumpy due to H bonds) Heinz et al. J. Am. Chem. Soc. 2003, 125, Heinz et al. Chem. Mater. 2007, 19,

5 Strain field in experiment Identify Atomic Positions and Structure in Alloys and Carbides By Imaging Plus Simulation Strain field in MD simulation 3D structure of a WC x tip containing amorphous carbon inclusions: x ~0.15 at surface and ~8 layers penetration With Jianwei Miao, UCLA, U. Dahmen, LBL, W. Ercius, Birmingham (UK) Imaged at TEAM I (currently largest EM) Xu et al. Nat. Mater. 2015, 14,

6 Understand Mechanisms of Cement Hydration (CSH) with Polycarboxylate Ethers (100) surface of tobermorite 14 Å 6

7 Supply Realistic, ph-resolved Surface Models Example: Silica Surface Model Database Typical: Q3 surfaces, 4.7 SiO(H,Na) per nm 2, with 0-20% ionization Si O O - Na + H 2 nm 0% ionized 4.7 OH/nm 2 (pzc) ph~4 for 20 nm particle ph~2.5 for 400 nm particle * 9% ionized ph~7 for 20 nm particle ph~5 for 400 nm particle 18% ionized ph~9 for 20 nm particle ph~7 for 400 nm particle Amorphous Q3, Q3/Q4, Q2 surfaces with 0-20% ionization Emami, Perry, and Heinz et al. Chem. Mater. 2014, 26,

8 Understand Nanocrystal Growth Example: Hydroxyapatite Biomineralization Exptl data from C. Tamerler, U Kansas (020) Adsorption energy (kcal/mol) Peptide HABP 1 strong binding (MLPHHGA) HAp (001) HAp (101) HAp (010) HAp (020) HAp cleaved surface (020) Adsorption energy (kcal/mol) Peptide HABP 2 nonbinding (NPGFAQA) 14 HAp (001) HAp (101) HAp (010) HAp (020) HAp cleaved surface 5 (020) 8

9 Explain Molecular Control Over Pt Nanocrystal Shape Using a Phenyl Molecular Switch Binding contrast between {111} and {100} surfaces determines preferred shape With Y. Huang, UCLA Synthesis from H 2 PtCl 6 with sodium borohydride and ascorbic acid in the presence of peptides Y. Huang and H. Heinz et al. Nano Letters 2013, 13, 840. Ramezani-Dakhel et al. Adv. Funct. Mater. 2015, 25,

10 Discover Mechanism of Mineral Agglomeration and Working Principle of Grinding Aids (Ca 3 SiO 5 ) 0.5 nm thin organic layer eliminates >90% of attractive Coulomb forces Up to 70% reduction in cohesive energy of hydroxylated (040) cleavage plane by grinding aids Significant differences among molecules depending on surfacespecific mitigation of local electric fields Agglomeration Energy, mj/m HC: Hydroxylated C 3 S C 3 S HC HC-Gly HC-TEA HC-TIPA HC-MDIPA Heinz, Farmer et al. J. Chem. Phys. 2006, 124, Mishra, Flatt, Heinz J. Phys. Chem. C 2013, 117, Sandmeyer Award (SCS 2016). 10