Metastability in pressure-induced structural transformations of CdSe/ZnS core/shell nanocrystals.
The kinetics and thermodynamics of structural transformations under pressure depend strongly on particle size due to the influence of surface free energy. By suitable design of surface structure, composition, and passivation it is possible, in principle, to prepare nanocrystals in structures inaccessible to bulk materials. However, few realizations of such extreme size-dependent behavior exist. Here, we show with molecular dynamics computer simulation that in a model of CdSe/ZnS core/shell nanocrystals the core high-pressure structure can be made metastable under ambient conditions by tuning the thickness of the shell. In nanocrystals with thick shells, we furthermore observe a wurtzite to NiAs transformation, which does not occur in the pure bulk materials. These phenomena are linked to a fundamental change in the atomistic transformation mechanism from heterogeneous nucleation at the surface to homogeneous nucleation in the crystal core.
Department of Chemistry, University of California, Berkeley, California 94720, United States. michael.gruenwald@berkeley.edu
Michael
M
Grünwald
Katie
K
Lutker
A Paul
AP
Alivisatos
Eran
E
Rabani
Phillip L
PL
Geissler
D019187:Cadmium Compounds / Q000737:chemistry*; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011312:Pressure; D018036:Selenium Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013816:Thermodynamics; D017967:Zinc Compounds / Q000737:chemistry*
D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C058667:cadmium selenide; C031238:zinc sulfide