The wurtzite to rock salt structural transformation in CdSe nanocrystals under high pressure

Journal Article · Wed Mar 15 04:00:00 EST 1995 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.469512· OSTI ID:6767587

Tolbert, S H; Alivisatos, A P ^[1]

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1. Materials Sciences Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720 (United States)

Structural transformations in CdSe nanocrystals are studied using high pressure x-ray diffraction and high pressure optical absorption at room temperature. The nanocrystals undergo a wurtzite to rock salt transition analogous to that observed in bulk CdSe. Both the thermodynamics and the kinetics of the transformation, however, are significantly different in finite size. The nanocrystal phase transition pressures vary from 3.6 to 4.9 GPa for crystallites ranging from 21 to 10 A in radius, respectively, in comparison to a value of 2.0 GPa for bulk CdSe. The size dependent data can be modeled using thermodynamics when surface energies are accounted for. Surface energies calculated in this way can be used to understand the dynamic microscopic path followed by atoms during the phase transition. X-ray diffraction data also shows that unlike bulk CdSe, crystalline domain size is conserved upon multiple transition in the nanocrystals, indicating that the transition only nucleates once in each nanocrystal.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6767587
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 102:11; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ABSORPTION SPECTRA
CADMIUM COMPOUNDS
CADMIUM SULFIDES
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL-PHASE TRANSFORMATIONS
DIFFRACTION
ENERGY
FREE ENERGY
INORGANIC PHOSPHORS
NUCLEATION
PHASE TRANSFORMATIONS
PHOSPHORS
PHYSICAL PROPERTIES
PRESSURE DEPENDENCE
SCATTERING
SIZE
SPECTRA
SULFIDES
SULFUR COMPOUNDS
SURFACE ENERGY
SURFACE PROPERTIES
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
VERY HIGH PRESSURE
X-RAY DIFFRACTION