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Now showing items 72-91 of 122

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    Large-scale molecular dynamics simulations of shock induced plasticity in tantalum single crystals 

    Ravelo, Ramon; An, Qi; Germann, Timothy C.; Holian, Brad Lee (AIP Publishing, 2012)
    We report on large-scale non-equilibrium molecular dynamics (NEMD) simulations of shock wave compression in Ta single crystals. The atomic interactions are modeled via a recently developed and optimized embedded-atom method ...
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    Large-scale molecular simulations of hypervelocity impact of materials 

    Jaramillo-Botero, Andres; An, Qi; Theofanis, Patrick L.; Goddard III, William A. (Elsevier, 2013)
    We describe the application of the ReaxFF reactive force field with short-range distance-dependent exponential inner wall corrections and the non-adiabatic electron Force Field (eFF) for studying the hypervelocity impact ...
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    Large-scale, long-term nonadiabatic electron molecular dynamics for describing material properties and phenomena in extreme environments 

    Jaramillo?Botero, Andres; Su, Julius; Qi, An; Goddard III, William A. (2010 Wiley Periodicals, Inc., 2011)
    We describe the first principle-based electron force field (eFF) methodology for modeling the simultaneous dynamics of electrons and nuclei (eMD) evolving nonadiabatically under transient extreme conditions. We introduce ...
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    Left-right loading dependence of shock response of (111)//(112) Cu bicrystals: Deformation and spallation 

    An, Q.; Han, W. Z.; Luo, S. N.; Germann, T. C.; Tonks, D. L.; Goddard III, William A. (AIP Publishing, 2012)
    We investigate with molecular dynamics the dynamic response of Cu bicrystals with a special asymmetric grain boundary (GB), (111)//(112)?110?, and its dependence on the loading directions. Shock loading is applied along ...
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    Light irradiation induced brittle-to-ductile and ductile-to-brittle transition in inorganic semiconductors 

    Wang, Hongwei; Morozov, Sergey; Goddard, William A.; An, Qi (Physical Review B, 2019)
    The intrinsic brittleness of inorganic semiconductors prevents them from extended engineering applications under extreme conditions of high temperature and pressure, making it essential to improve their ductility. Here, ...
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    Locating Si atoms in Si-doped boron carbide: A route to understand amorphization mitigation mechanism 

    Khan, Atta U.; Etzold, Anthony M.; Yang, Xiaokun; Domnich, Vladislav; Xie, Kelvin Y.; Hwang, Chawon; Behler, Kristopher D.; Chen, Mingwei; An, Qi; LaSalvia, Jerry C. (Elsevier, 2018)
    he well-documented formation of amorphous bands in boron carbide (B4C) under contact loading has been identified in the literature as one of the possible mechanisms for its catastrophic failure. To mitigate amorphization, ...
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    Mechanical properties in thermoelectric oxides: Ideal strength, deformation mechanism, and fracture toughness 

    Li, Guodong; Aydemir, Umut; Morozov, Sergey I.; Miller, Samuel A.; An, Qi; Goddard III, William A.; Zhai, Pengcheng; Zhang, Qingjie; Snyder, G. Jeffrey (Elsevier, 2018)
    The recent dramatic improvements in high-performance thermoelectric (TE) oxides provide new exciting applications in the TE field, but the mechanical properties so important for engineering applications remain largely ...
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    Mechanical softening of thermoelectric semiconductor Mg2Si from nanotwinning 

    Li, Guodong; An, Qi; Morozov, Sergey I.; Duan, Bo; Goddard III, William A.; Zhai, Pengcheng; Zhang, Qingjie; Snyder, G. Jeffrey (Elsevier, 2018)
    Nanotwinning exhibits strengthening effects in many metals, semiconductors, and ceramics. However, we show from ab-initio calculations that nanotwins significantly decrease the strength of thermoelectric semiconductor ...
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    Mechanism and kinetics of the electrocatalytic reaction responsible for the high cost of hydrogen fuel cells 

    Cheng, Tao; Goddard, William A.; An, Qi; Xiao, Hai; Merinov, Boris; Morozov, Sergey (Royal Society of Chemistry, 2017)
    The sluggish oxygen reduction reaction (ORR) is a major impediment to the economic use of hydrogen fuel cells in transportation. In this work, we report the full ORR reaction mechanism for Pt(111) based on Quantum Mechanics ...
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    Microalloying boron carbide with silicon to achieve dramatically improved ductility 

    An, Qi; Goddard III, William A. (American Chemical Society, 2014)
    Boron carbide (B4C) is a hard material whose value for extended engineering applications such as body armor
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    Mixed anionic surfactant-templated mesoporous silica nanoparticles for fluorescence detection of Fe3+ 

    Gai, Fangyuan; Zhou, Tianlei; Chu, Guang; Li, Ye; Liu, Yunling; Huo, Qisheng; Akhtar, Farid (2016)
    This work demonstrates a novel method for the synthesis of large pore mesoporous silica nanoparticles (MSNs) with a pore diameter of 10.3 nm and a particle diameter of similar to 50 nm based on the incorporation of mixed ...
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    Nanometallic glasses: size reduction brings ductility, surface state drives its extent 

    Chen, David Z.; Jang, Dongchan; Guan, Kelly M.; An, Q.; Goddard III, W. A.; Greer, Julia R. (American Chemical Society, 2013)
    We report tensile experiments on Ni80P20 metallic glass samples fabricated via a templated electroplating process and via focused ion beam milling, which differed only in their surface energy states: Ga-ion-irradiated and ...
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    Nanotwinned Boron Suboxide (B6O): New Ground State of B6O 

    An, Qi; Reddy, K. Madhav; Dong, Huafeng; Chen, Ming-Wei; Oganov, Artem R.; Goddard III, William A. (American Chemical Society, 2016)
    Nanotwinned structures in superhard ceramics rhombohedral boron suboxide (R-B6O) have been examined using a combination of transmission electron microscopy (TEM) and quantum mechanics (QM). QM predicts negative relative ...
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    Nanotwinning and amorphization of boron suboxide 

    Kunka, Cody; An, Qi; Rudawski, Nicholas; Subhash, Ghatu; Zheng, James; Halls, Virginia; Singh, Jogender (Elsevier, 2018)
    Recently, researchers discovered that in contrast to isolated twins, periodic twins with nanoscale spacing can dramatically improve mechanical properties. Ceramics engineers now seek to incorporate this “nanotwinning” into ...
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    Nanotwins soften boron-rich boron carbide (B13C2) 

    An, Qi; Goddard III, William A. (AIP Publishing, 2017)
    Extensive studies of metals and alloys have observed that nanotwins lead to strengthening, but the role of nanotwins in ceramics is not well established. We compare here the shear strength and the deformation mechanism of ...
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    Nanotwins soften boron-rich boron carbide (B13C2) 

    An, Qi; Goddard, William A. (2017)
    Extensive studies of metals and alloys have observed that nanotwins lead to strengthening, but the role of nanotwins in ceramics is not well established. We compare here the shear strength and the deformation mechanism of ...
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    New ground-state crystal structure of elemental boron 

    An, Qi; Reddy, K. Madhav; Xie, Kelvin Y.; Hemker, Kevin J.; Goddard III, William A. (American Physical Society, 2016)
    Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic ...
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    Nucleation of amorphous shear bands at nanotwins in boron suboxide 

    An, Qi; Reddy, K. Madhav; Qian, Jin; Hemker, Kevin J.; Chen, Ming-Wei; Goddard III, William A. (Nature Research, 2016)
    The roles of grain boundaries and twin boundaries in mechanical properties are well understood for metals and alloys. However, for covalent solids, their roles in deformation response to applied stress are not established. ...
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    Ordering and dimensional crossovers in metallic glasses and liquids 

    Chen, David Z.; An, Qi; Goddard III, William A.; Greer, Julia R. (American Physical Society, 2017)
    The atomic-level structures of liquids and glasses are amorphous, lacking long-range order. We characterize the atomic structures by integrating radial distribution functions (RDF) from molecular dynamics (MD) simulations ...
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    The Photoelectrochemical and Photocatalytic Properties of Tantalum Oxide and Tantalum Nitride 

    Khanal, Vijay; Irani, Rowshanak; Fiechter, Sebastian; Abdi, Fatwa F.; Subramanian, Vaidyanathan (Journal of The Electrochemical Society, 2019)
    The surfactant-assisted synthesis of tantalum oxide nanoparticles (Ta2O5), its subsequent nitridation to form tantalum nitride (Ta3N5), and the evaluation of the photoactivity of these nanoparticles, are presented. The ...