The energetics of prenucleation clusters in lattice solutions

Journal Article · Thu Dec 01 00:00:00 EST 2016 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4964489· OSTI ID:1330117

Legg, Benjamin A. ^[1]; De Yoreo, James J. ^[2]

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1. Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
2. Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA, Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA

According to classical nucleation theory, nucleation from solution involves the formation of small atomic clusters. Most formulations of classical nucleation use continuum “droplet” approximations to describe the properties of these clusters. However, the discrete atomic nature of very small clusters may cause deviations from these approximations. Here, we present a self-consistent framework for describing the nature of these deviations. We use our framework to investigate the formation of “polycube” atomic clusters on a cubic lattice, for which we have used combinatoric data to calculate the thermodynamic properties of clusters with 17 atoms or less. We show that that the classical continuum droplet model emerges as a natural approach to describe the free energy of small clusters; but with a size-dependent surface tension. However, this formulation only arises if an appropriate “site-normalized” definition is adopted for the free energy of formation. These results are independently confirmed through the use of Monte Carlo calculations. Our results show that clusters formed from sparingly soluble materials (μM solubility range) tend to adopt compact configurations that minimize the solvent-solute interaction energy. As a consequence, there are distinct minima in the cluster-size-energy landscape that correspond to especially compact configurations. Conversely, highly soluble materials (1 M) form clusters with expanded configurations that maximize configurational entropy. The effective surface tension of these clusters tends to smoothly and systematically decrease as cluster size increases. However, materials with intermediate solubility (1 mM) are found to have a balanced behavior, with cluster energies that follow the classical ‘droplet’ scaling laws remarkably well.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1330117
• Alternate ID(s): OSTI ID: 1368135; OSTI ID: 1420691
• Report Number(s): PNNL-SA-118541; JCPSA6; 10.1063/1.4964489
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Vol. 145 Journal Issue: 21; ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY