Browsing by Author "Liu, Mingjie"

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    Computational Study of Carbon-Based Low-Dimensional Materials on Structures, Properties and Applications
    (2016-08-30) Liu, Mingjie; Yakobson, Boris I
    Low-dimensional materials including both 1D and 2D scenarios exhibit unique properties distinguished from their bulk states. In this thesis, computational modeling of low-dimensional materials on their structures, properties and applications has been investigated. First-principles simulations are employed to investigate the following topics. First of all in the 1D scenario, a comprehensive study on carbyne-one dimensional carbon chain-from its structure to properties has been conducted, and the extreme mechanical performance and intriguing metal-insulator transition under tension has been demonstrated. The properties of proposed 1D boron nanostructures have also been investigated and a constant-tension structural transition between two boron phases has been revealed. Secondly, two examples for the energy application of low-dimensional materials have been presented. The first example contains the energy storage with graphene and its derivatives applied in Li-ion batteries as well as the examination on the lithium nucleation process on graphene. The second example is the exploration of the energy conversion with N-doped carbon materials as effective catalysts in electrochemical reduction of CO2. Lastly, the simplified model- jellium model- has been applied in carbon nanotube growth. The termination effect and the chiral selectivity in CNT growth have been investigated.
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    A jellium model of a catalyst particle in carbon nanotube growth
    (AIP Publishing, 2017) Artyukhov, Vasilii I.; Liu, Mingjie; Penev, Evgeni S.; Yakobson, Boris I.
    We show how a jellium model can represent a catalyst particle within the density-functional theory based approaches to the growth mechanism of carbon nanotubes (CNTs). The advantage of jellium is an abridged, less computationally taxing description of the multi-atom metal particle, while at the same time in avoiding the uncertainty of selecting a particular atomic geometry of either a solid or ever-changing liquid catalyst particle. A careful choice of jellium sphere size and its electron density as a descriptive parameter allows one to calculate the CNT–metal interface energies close to explicit full atomistic models. Further, we show that using jellium permits computing and comparing the formation of topological defects (sole pentagons or heptagons, the culprits of growth termination) as well as pentagon–heptagon pairs 5|7 (known as chirality-switching dislocation).
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    New insights into the properties and interactions of carbon chains as revealed by HRTEM and DFT analysis
    (Elsevier, 2014) Casillas, Gilberto; Mayoral, Alvaro; Liu, Mingjie; Ponce, Arturo; Artyukhov, Vasilii I.; Yakobson, Boris I.; Jose-Yacaman, Miguel
    Atomic carbon chains have raised interest for their possible applications as graphene interconnectors as the thinnest nanowires; however, they are hard to synthesize and subsequently to study. We present here a reproducible method to synthesize carbon chains in situ TEM. Moreover, we present a direct observation of the bond length alternation in a pure carbon chain by aberration corrected TEM. Also, cross bonding between two carbon chains, 5ﾠnm long, is observed experimentally and confirmed by DFT calculations. Finally, while free standing carbon chains were observed to be straight due to tensile loading, a carbon chain inside the walls of a carbon nanotube showed high flexibility.