Browsing by Author "Ngoepe, Phuti E."

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    Generating structural distributions of atomistic models of Li2O nanoparticles using simulated crystallisation
    (Royal Society of Chemistry, 2010-12-31T00:00:00Z) Sayle, Thi X. T.; Ngoepe, Phuti E.; Sayle, Dean C.
    Simulated crystallisation has been used to predict that Li2O nanoparticles comprise octahedral morphologies bounded by {111} and truncated by {100} with inverse fluorite crystal structure. We observe that by changing the temperature of the (simulated) crystallisation, changes in the microstructure can be realised, such a strategy facilitates the generation of full atomistic models with microstructural distributions similar to the structural diversity observed synthetically.
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    Simulating Mn02 nanoparticles using simulated amorphisation and recrystallisation
    (American Chemical Society , 2011-03-18) Sayle, Thi X. T.; Catlow, C. Richard A.; Maphanga, R. Regina; Ngoepe, Phuti E.; Sayle, Dean C.
    Models of MnO2 nanoparticles, with full atomistic detail, have been generated using a simulated amorphization and recrystallization strategy. In particular, a 25,000-atom “cube” of MnO2 was amorphized (tension-induced) under molecular dynamics (MD). Long-duration MD, applied to this system, results in the sudden evolution of a small crystalline region of pyrolusite-structured MnO2, which acts as a nucleating “seed” and facilitates the recrystallization of all the surrounding (amorphous) MnO2. The resulting MnO2 nanoparticle is about 8 nm in diameter, conforms to the pyrolusite structure (isostructural with rutile TiO2, comprising 1 × 1 octahedra) is heavily twinned and comprises a wealth of isolated and clustered point defects such as cation vacancies. In addition, we suggest the presence of ramsdellite (2 × 1 octahedra) intergrowths. Molecular graphical snapshots of the crystallization process are presented.