杂原子对石墨烯热力学性质影响的研究
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摘要
本文采用密度泛函理论优化了含杂原子单层石墨烯的结构,并计算了相关热力学性质。研究了相关石墨烯的结构稳定性、比热容、声子谱、内能、熵、焓等热物理性质,并比较了异种原子对单层石墨烯热力学性质的影响.结果表明,杂原子单层石墨烯都较完整的单层石墨烯的稳定性较差.在声子态密度谱图中,含杂原子的石墨烯较完美石墨烯显示出更多的峰.石墨烯的热力学函数都有随温度变化而变化的情况。石墨烯的比热容随温度升高而呈逐渐升高的趋势,且在高温时比热容趋于恒定.含杂原子单层石墨烯与完整单层石墨烯相比,低温时具有较高的自由能,而高温时具有较低的自由能。石墨烯的熵随温度升高呈现逐渐升高的趋势。在温度相同时,含杂原子的石墨烯与完整石墨烯相比,具有更高的比热容和内能和熵。
The structures of the graphene with Heteroatoms were optimized and the thermodynamic properties of the graphene were calculated by density functional theory. The phonon density of states,structure stability, specific heat, Helmholtz free energy, entropy and internal energy were studied and compared each other to analyze how the heteroatoms affect the thermodynamic properties of a single layer graphene. The results show that the perfect graphene is more stable than that with heteroatom.There are more peaks in the curve of imperfect graphene than that of perfect graphene in the phonon density of states. For the thermodynamic properties of the graphene, the thermodynamic functions change with the temperature. At lower temperature, the specific heat of the graphene increases evidently with the temperature, while it changes slightly at high temperature. It is in contrast for the Helmholtz free energy. The entropy and internal energy of the graphene with heteroatoms are higher than those of the perfect graphene at the same temperature.
The structures of the graphene with Heteroatoms were optimized and the thermodynamic properties of the graphene were calculated by density functional theory. The phonon density of states,structure stability, specific heat, Helmholtz free energy, entropy and internal energy were studied and compared each other to analyze how the heteroatoms affect the thermodynamic properties of a single layer graphene. The results show that the perfect graphene is more stable than that with heteroatom.There are more peaks in the curve of imperfect graphene than that of perfect graphene in the phonon density of states. For the thermodynamic properties of the graphene, the thermodynamic functions change with the temperature. At lower temperature, the specific heat of the graphene increases evidently with the temperature, while it changes slightly at high temperature. It is in contrast for the Helmholtz free energy. The entropy and internal energy of the graphene with heteroatoms are higher than those of the perfect graphene at the same temperature.
引文
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[3] Sreejith S, Ma X, Zhao Y. Graphene Oxide Wrapping on Squaraine-loaded Mesoporous Silica Nanoparticles for Bioimaging[J]. Journal of the American Chemical Society,2012, 134(42):17346-17349
[4] Bai S, Chen S Q, Shen X P, Zhu G X, Wang G X.Nanocomposites of Hematite(alpha-Fe_2O_3)Nanospindles with Crumpled Reduced Graphene Oxide Nanosheets as High-performance Anode Material for Lithium-ion Batteries[J]. Rsc Advances, 2012, 2(29):10977-10984
[5] Fu W, Chen C N. A Facile One-Step Hydrothermal Method to Produce Graphene Oxide/Fe_2O_3-nanotubes Composites and its Electrochemical Properties[J]. Nano,2012, 7(4):1250032
[6] Huang Z, Fisher T, Murthy J. An Atomistic Study of Thermal Conductance Across a Metal-graphene Nanoribbon Interface[J]. Journal of Applied Physics, 2011,109(7):074305
[7] Xue X Y, Ma C H, Cui C X, Xing L L. High Lithium Storage Performance of Alpha-Fe_2O_3/graphene Nanocomposites as Lithium-ion Battery Anodes[J]. Solid State Sciences, 2011, 13(8):1526-1530
[8] Song H J, Jia X H, Li N, Yang X F, Tang H. Synthesis of alpha-Fe_2O_3 Nanorod/graphene Oxide Composites and Their Tribological Properties[J]. Journal of Materials Chemistry, 2012, 22(3):895-902
[9] Wang D W, Li Y Q, Wang Q H, Wang T M. Nanostructured Fe_2O_3-graphene Composite as a Novel Electrode Material for Supercapacitors[J]. Journal of Solid State Electrochemistry, 2012, 16(6):2095-2102
[10] Wang G, Liu T, Luo Y J, Zhao Y, Ren Z Y, Bai J B,Wang H. Preparation of Fe_2O_3/graphene Composite and its Electrochemical Performance as an Anode Material for Lithium Ion Batteries[J]. Journal of Alloys and Compounds, 2011, 509(24):L216-L220
[11] Gholizadeh R, Yu Y X. Work Functions of Pristine andHeteroatom-doped Graphenes Under Different External Electric Fields:an ab Initio DFT Study[J]. Journal of Physical Chemistry C, 2014, 118(48):28274-28282
[12] Ghosh S, Calizo I, Teweldebrhan D, Lau J. Extremely High Thermal Conductivity of Graphene:Prospects for Thermal Management Applications in Nanoelectronic Circuits[J]. Applied Physics Letters, 2008, 92(15):151911
[13] Jiang J, Wang J, Li B. Thermal Conductance of Graphene and Dimerite[J]. Physical Review. B, Condensed Matter,2009, 79(20):205418
[14] Nika D L, Pokatibv E P, Askerov A S, et al. Phonon Thermal Conduction in Graphene Role of Umklapp and Edge Roughness scattering[J]. Physical Review, 2009, 79(15):155413
[15] Akhoondali H, Goharrizi A Y, Sharifi M J. Combined Effect of Edge Roughness and Phonon Scattering on the Electronic Properties of Ultrascaled Graphene Nanoribbons[J]. Superlattices and Microstructures, 2014,75(7):268-277
[16] Begum K R, Sankeshwar N S. Electronic Thermal Conduction in Suspended Graphene[J]. Physica E:Lowdimensional Systems and Nanostructures, 2015, 73(5):27-34
[17] Wang J F, Xie H Q, Guo Z X. First-principles Investigation on Thermal Properties and Infrared Spectra of Imperfect Graphene[J]. Applied Thermal Engineering, 2017,116(4):456-462
[18] Novoselov K S, Geim A K, Morozov S V, Jiang D, Zhang Y, Dubonos S V,Grigorieva I V,Firsov A A. Electric Field Effect in Atomically Thin Carbon Films[J]. Science, 2004,306(22):666-669