Structure and phase behavior of colloidal dumbbells with tunable attractive interactions.
Phys Chem Chem Phys
; 15(47): 20590-9, 2013 Dec 21.
Article
in En
| MEDLINE
| ID: mdl-24185816
ABSTRACT
We investigate thermodynamic and structural properties of colloidal dumbbells in the framework provided by the Reference Interaction Site Model (RISM) theory of molecular fluids and Monte Carlo simulations. We consider two different models in the first one we set identical square-well attractions on the two tangent spheres constituting the molecule (SW-SW model); in the second scheme, one of the square-well interactions is switched off (HS-SW model). Appreciable differences emerge between the physical properties of the two models. Specifically, the k â 0 behavior of SW-SW structure factors S(k) points to the presence of a gas-liquid coexistence, as confirmed by subsequent fluid phase equilibria calculations. Conversely, the HS-SW S(k) develops a low-k peak, signaling the presence of aggregates; such a process destabilizes the gas-liquid phase separation, promoting at low temperatures the formation of a cluster phase, whose structure depends on the system density. We further investigate such differences by studying the phase behavior of a series of intermediate models, obtained from the original SW-SW by progressively reducing the depth of one square-well interaction. RISM structural predictions positively reproduce the simulation data, including the rise of S(k â 0) in the SW-SW model and the low-k peak in the HS-SW structure factor. As for the phase behavior, RISM agrees with Monte Carlo simulations in predicting a gas-liquid coexistence for the SW-SW model (though the critical parameters appear overestimated by the theory) and its progressive disappearance when moving toward the HS-SW model.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Type of study:
Prognostic_studies
Language:
En
Journal:
Phys Chem Chem Phys
Journal subject:
BIOFISICA
/
QUIMICA
Year:
2013
Document type:
Article
Affiliation country:
Italy
Country of publication:
ENGLAND
/
ESCOCIA
/
GB
/
GREAT BRITAIN
/
INGLATERRA
/
REINO UNIDO
/
SCOTLAND
/
UK
/
UNITED KINGDOM