Purton JA, Parker SC, Allan NL. Monte Carlo simulation and free energies of mixed oxide nanoparticles.
Phys Chem Chem Phys 2013;
15:6219-25. [PMID:
23515460 DOI:
10.1039/c3cp50388g]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A Monte Carlo Exchange technique is used to study the thermodynamic properties of MgO-MnO nanoparticles ranging in size from 1728 to 21,952 ions. The solubility of Mg(2+) is much greater in MnO than the reverse, reflecting the difference in size between the two cations. The solubility, for a given temperature, diminishes with nanoparticle size. As the Mn concentration is progressively increased the Mn(2+) ions occupy the corners, edges and then surface sites of the nanoparticle before entering subsurface layers. We do not observe any pronounced ordering of the cations within the body of the nanoparticles themselves. The enthalpies of forming ternary nanoparticles from particles of MgO and MnO of the same size vary with the size of the nanoparticle and become more positive for a given concentration as the particle size increases. Free energies of mixing of the two end-member nanoparticles have been determined using the semigrand ensemble. The consolute temperature (the temperature above which there is complete miscibility) increases non-linearly with the size of the nanoparticle by approximately 70% over the size range considered.
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