Faceting Transition of Gold Nano Materials
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Faceting Transition of Gold Faceting Transition of Gold Nano Materials Nano Materials Yanting Wang Advisors: Prof. Stephen Teitel, Prof. Christoph Dellago May 22, 2003 Department of Physics and Astronomy University of Rochester Introduction Introduction Simulation of morphological Simulation of morphological and structural change of and structural change of gold nanorods gold nanorods Faceting Transition of gold Faceting Transition of gold cluster cluster Faceting Transition of gold Faceting Transition of gold nanorods nanorods Conclusion and future work Conclusion and future work
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Faceting Transition of Gold Nano Materials. Yanting Wang. Advisors: Prof. Stephen Teitel, Prof. Christoph Dellago. Introduction Simulation of morphological and structural change of gold nanorods Faceting Transition of gold cluster Faceting Transition of gold nanorods - PowerPoint PPT Presentation
Transcript of Faceting Transition of Gold Nano Materials
Faceting Transition of Gold Nano MaterialsFaceting Transition of Gold Nano Materials
Yanting Wang
Advisors: Prof. Stephen Teitel, Prof. Christoph Dellago
May 22, 2003
Department of Physics and AstronomyUniversity of Rochester
IntroductionIntroductionSimulation of morphological and Simulation of morphological and structural change of gold nanorodsstructural change of gold nanorodsFaceting Transition of gold clusterFaceting Transition of gold clusterFaceting Transition of gold nanorodsFaceting Transition of gold nanorodsConclusion and future workConclusion and future work
Wide range of applicationsWide range of applicationsLaser heating experiments of rodsLaser heating experiments of rods
Shorter and wider inter. ParticlesShorter and wider inter. ParticlesInternal point and planar defectsInternal point and planar defects
MD simulation of heating rodsMD simulation of heating rodsMeta-stable intermediate stateMeta-stable intermediate stateFcc-hcp structural changeFcc-hcp structural change
Faceting transition of ih gold clusterFaceting transition of ih gold clusterFacets vanish below TFacets vanish below T
mm
Faceting transition of gold nanorodsFaceting transition of gold nanorodsSome evidence of connection Some evidence of connection
between faceting and Tbetween faceting and Tss
IntroductionIntroduction
Wang, Z. L. et al., Surf. Sci. 1999, 440, L809.Link, S. et al., J. Phys. Chem. B 2000, 104, 6152.Link, S. et al., J. Phys. Chem. B 2000, 104, 7867.
Simulation of Morphological and Simulation of Morphological and Structural Change of Gold NanorodsStructural Change of Gold Nanorods
Experiments: more than 106 atomsSimulation:1404-11076 atoms
Colored by local structure: yellow --fcc green --hcp red --others
Faceting Transition of Icosahedral Gold ClusterFaceting Transition of Icosahedral Gold Cluster
Cooled from liquid obtaining ih cluster, then heated up.Equilibrated at each temperature by constant T MD.
Colored by local structure: yellow --fccgreen --hcpgray --decahedron
Tm~1090K
T=100K T=1500K
??
Average shape of ih gold clusterAverage shape of ih gold cluster
400K 600K 900K 1000K 1050K 1075K
Cone algorithmCone algorithm Multi-layersMulti-layers Local curvature fittingLocal curvature fitting
Average shapeAverage shape
Colored by larger local curvature with warmer color represents larger curvature.
Surface diffusion of ih gold clusterSurface diffusion of ih gold cluster
Mean squared displacementsMean squared displacements
Interlayer diffusionInterlayer diffusion Surface structureSurface structure Bulk structureBulk structure
Faceting transition point?Faceting transition point?
Definition of Definition of faceting transition faceting transition pointpoint
Larger local curvature Larger local curvature distributiondistribution
Geometrical Geometrical difficulties of defining difficulties of defining faceting transition faceting transition point for nano clusterspoint for nano clusters
Standard deviation
Normalized distribution
Small cluster sizeAsymmetric facets and edgesMacroscopic shape fluctuationLarge influence of surface atom's thermal fluctuation to the macroscopic shape
No angular discontinuities.
Not a good interpretation!
Faceting Transition of Gold NanorodFaceting Transition of Gold Nanorod
N=11076 Ts~990K T
m~1280K
Colored by larger local curvature with warmer color represents larger curvature.
ConclusionConclusion
Icosahedral gold clusterIcosahedral gold clusterThe vertices, edges and facets get rounder with higher The vertices, edges and facets get rounder with higher temperature and totally disappear below Ttemperature and totally disappear below T
mm..
Faceting transition occurs before bulk melting.Faceting transition occurs before bulk melting.Surface becomes unstructured at higher temperature than that Surface becomes unstructured at higher temperature than that of surface diffusion.of surface diffusion.
Gold nanorodGold nanorodMacroscopic shape transformations are intimately connected Macroscopic shape transformations are intimately connected with the faceting transition occurring on the sides of the rod.with the faceting transition occurring on the sides of the rod.
Future WorkFuture Work
Icosahedral gold clusterIcosahedral gold clusterDefine faceting transition for small size nano cluster.Define faceting transition for small size nano cluster.Quantify faceting transition geometrically and find the Quantify faceting transition geometrically and find the transition temperature.transition temperature.
Gold NanorodGold NanorodDetailed analysis of surface atom behavior.Detailed analysis of surface atom behavior.Quantify faceting transition geometrically.Quantify faceting transition geometrically.Find out the energetic relation between surface behavior and Find out the energetic relation between surface behavior and internal structural change.internal structural change.
