载能氢原子与单层石墨碰撞过程的分子动力学研究
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摘要
在高温热核聚变装置中,偏滤器发挥着不可替代的作用；同时,碳基材料因具有良好的热机械性能和低原子序数而作为国际热核聚变反应堆(ITER)中偏滤器的备选材料之一。但是碳基材料与氢原子(或氢同位素)反应产生的高化学腐蚀率和滞留问题,阻碍着其在燃烧聚变装置中应用。因此,碳基材料的化学腐蚀行为需要深入研究。
通常,轰击到偏滤器靶面的氢原子的能量范围在100 eV以下；在这一能量范围内,碳氢粒子间的碰撞反应不能应用Trim及其变体程序计算。目前,没有一种宏观的理论计算模型可以合理的解释低能量氢原子与碳基材料的化学腐蚀机理,另一方面,只有研究碳氢键的形成、断裂和键能变化才能解释化学腐蚀机理。Brenner等人建立了可以很好的描述金刚石的薄膜沉积过程的半经验键序势能函数。最近,人们采用Brenner势研究碳氢粒子间的化学腐蚀和氢(或其同位素)滞留。然而,到目前为止,关于碳基材料化学腐蚀的理论知识依旧很匮乏。为此,本人采用Brenner势,编写可以描述碳氢系统的分子动力学程序,深入研究了载量氢原子与单层石墨间碰撞过程。
论文的第一部分研究低能量氢原子与单层石墨晶体之间的碰撞过程。为了考虑石墨晶体的结构对碳氢原子间的碰撞过程,以及入射氢原子的入射位置及能量对碰撞过程的影响,在模拟中,选择石墨六角环上的三个对称点作为氢原子的初始入射位置(这三个点分别与能带理论中第一布里渊区的r,M,K三点对应)。氢与碳作用,会发生不同的碰撞过程：入射粒子或被吸附,或被反射,或被穿透。研究发现,入射氢原子的能量若小于0.35 eV,所有的氢原子均被单层石墨反射；若氢原子被碳靶原子吸附,形成碳氢键,那么邻近的碳碳键变长,键能降低了1.2 eV。
论文的第二部分研究了单空位缺陷对石墨层中碳氢粒子间碰撞的影响。将氢原子以不同能量分别向单空位缺陷边缘的两个碳原子轰击,分析入射氢原子的能量损失、发生吸附反应的能量范围和靶原子的能量传递过程。研究发现：单空位缺陷边缘的碳氢粒子更易发生吸附反应；在碳氢粒子正碰过程中,氢原子随入射能量的改变出现了双反射区域；碳氢粒子在空位缺陷边缘吸附后,形成了高结合能的sp2结构,其邻近的碳碳键能未降低；单空位缺陷边缘的碳原子吸附能量的能力强,但传递能量的能力弱。这些结果对理解聚变反应中碳材料的高化学腐蚀及氚滞留有重要意义。
The divertor has been proved to be an essential part for a nuclear fusion reactor in handling large particle fluxes. Carbon based materials due to its excellent thermal resistance and low atomic number has been chosen as a primary material for the divertor target plates for the International Thermonuclear Experimental Reactor (ITER). However, two major issues-large erosion yield and hydrogen/tritium retention-are questioning whether the carbon-based materials can be used in future fusion devices. Further study on carbon-based materials is needed to answer the inescapable question.
As well known, the energy of the particles incident on the divertor plates seldom exceeds one hundred electron volts; this energy range cannot be described adequately by the potentials used in Trim code and its variants. Up to now no macroscopic theoretical model available can predict reasonably the sputtering yield of Carbon based materials caused by low-energy hydrogen impact. Microscopic model, taking into account the C-H bond forming and breaking, is desperately needed. Brenner et al. developed a set of reactive empirical bond-order (REBO) potentials and applied it successfully to studying chemical vapor growth of diamond. Recently, many studies have been carried out on C-H systems for explaining the chemical erosion of carbon-based materials and even hydrogen (or its isotope) retention. However, the knowledge of chemical erosion process of carbon-based materials is still limited.
We develop a molecular dynamic simulation code with REBO potential for analyzing chemical erosion processes of graphite. In the first part of this thesis, the collision processes between incident hydrogen atom and single graphite sheet are modeled in detail. Since the structure of graphene has great effects on the interaction between hydrogen and carbon, the energy and bombarding location of incident hydrogen atom are critical parameters. To characterize the structural effects, the high symmetrical points, corresponding toΓ, M, K in the energy band, are chosen as the impacting targets. The evolutions of kinetic and potential energy of incident hydrogen atom as well as C-C and C-H bond energy are evaluated during collision processes. The simulation results show that the interaction between hydrogen and carbon atom cannot be described theoretically by two-body approximation and must take into account the effects of multi-body interaction. At different incident locations, the states of incident hydrogen exhibit very different characteristics. The adsorption, reflection, and penetration coefficients of incident atoms are accessed. It is found that the incident hydrogen with energy lower than 0.35 eV is 100 percent reflected. When one hydrogen atom is adsorbed to one carbon atom, the bond energy of this carbon with its nearest neighbors is reduced by 1.2 eV from 4.9 eV.
In the second part of this thesis, the collision processes between one hydrogen atom and graphene with single vacancy defect have been investigated. Energy transfers between hydrocarbon particles have been studied during the collision processes at the edge of vacancy defects. Energy losses for C-C and C-H bond also have been studied. The results show:The monovacancy has a big influence on adsorption between hydrocarbon particles; In certain areas of the graphite sheet, an incident hydrogen atom can be reflected backwards in two different energy ranges; hydrocarbon particles, which adsorbed at the monovacancy edge, form a bond in sp2 configuration, without an overhang configuration. However, C-C bond energy does not reduce while previous work found that theirs bond energy decreased byl.2 eV during hydrocarbon bond forming. We also found that, the carbon atom, at the vacancy edge, has more capacity to absorb incident energy, but has less capacity to spread the gained energy. These results will be of great help to understand the chemical erosion and tritium retention in fusion devices.
通常,轰击到偏滤器靶面的氢原子的能量范围在100 eV以下；在这一能量范围内,碳氢粒子间的碰撞反应不能应用Trim及其变体程序计算。目前,没有一种宏观的理论计算模型可以合理的解释低能量氢原子与碳基材料的化学腐蚀机理,另一方面,只有研究碳氢键的形成、断裂和键能变化才能解释化学腐蚀机理。Brenner等人建立了可以很好的描述金刚石的薄膜沉积过程的半经验键序势能函数。最近,人们采用Brenner势研究碳氢粒子间的化学腐蚀和氢(或其同位素)滞留。然而,到目前为止,关于碳基材料化学腐蚀的理论知识依旧很匮乏。为此,本人采用Brenner势,编写可以描述碳氢系统的分子动力学程序,深入研究了载量氢原子与单层石墨间碰撞过程。
论文的第一部分研究低能量氢原子与单层石墨晶体之间的碰撞过程。为了考虑石墨晶体的结构对碳氢原子间的碰撞过程,以及入射氢原子的入射位置及能量对碰撞过程的影响,在模拟中,选择石墨六角环上的三个对称点作为氢原子的初始入射位置(这三个点分别与能带理论中第一布里渊区的r,M,K三点对应)。氢与碳作用,会发生不同的碰撞过程：入射粒子或被吸附,或被反射,或被穿透。研究发现,入射氢原子的能量若小于0.35 eV,所有的氢原子均被单层石墨反射；若氢原子被碳靶原子吸附,形成碳氢键,那么邻近的碳碳键变长,键能降低了1.2 eV。
论文的第二部分研究了单空位缺陷对石墨层中碳氢粒子间碰撞的影响。将氢原子以不同能量分别向单空位缺陷边缘的两个碳原子轰击,分析入射氢原子的能量损失、发生吸附反应的能量范围和靶原子的能量传递过程。研究发现：单空位缺陷边缘的碳氢粒子更易发生吸附反应；在碳氢粒子正碰过程中,氢原子随入射能量的改变出现了双反射区域；碳氢粒子在空位缺陷边缘吸附后,形成了高结合能的sp2结构,其邻近的碳碳键能未降低；单空位缺陷边缘的碳原子吸附能量的能力强,但传递能量的能力弱。这些结果对理解聚变反应中碳材料的高化学腐蚀及氚滞留有重要意义。
The divertor has been proved to be an essential part for a nuclear fusion reactor in handling large particle fluxes. Carbon based materials due to its excellent thermal resistance and low atomic number has been chosen as a primary material for the divertor target plates for the International Thermonuclear Experimental Reactor (ITER). However, two major issues-large erosion yield and hydrogen/tritium retention-are questioning whether the carbon-based materials can be used in future fusion devices. Further study on carbon-based materials is needed to answer the inescapable question.
As well known, the energy of the particles incident on the divertor plates seldom exceeds one hundred electron volts; this energy range cannot be described adequately by the potentials used in Trim code and its variants. Up to now no macroscopic theoretical model available can predict reasonably the sputtering yield of Carbon based materials caused by low-energy hydrogen impact. Microscopic model, taking into account the C-H bond forming and breaking, is desperately needed. Brenner et al. developed a set of reactive empirical bond-order (REBO) potentials and applied it successfully to studying chemical vapor growth of diamond. Recently, many studies have been carried out on C-H systems for explaining the chemical erosion of carbon-based materials and even hydrogen (or its isotope) retention. However, the knowledge of chemical erosion process of carbon-based materials is still limited.
We develop a molecular dynamic simulation code with REBO potential for analyzing chemical erosion processes of graphite. In the first part of this thesis, the collision processes between incident hydrogen atom and single graphite sheet are modeled in detail. Since the structure of graphene has great effects on the interaction between hydrogen and carbon, the energy and bombarding location of incident hydrogen atom are critical parameters. To characterize the structural effects, the high symmetrical points, corresponding toΓ, M, K in the energy band, are chosen as the impacting targets. The evolutions of kinetic and potential energy of incident hydrogen atom as well as C-C and C-H bond energy are evaluated during collision processes. The simulation results show that the interaction between hydrogen and carbon atom cannot be described theoretically by two-body approximation and must take into account the effects of multi-body interaction. At different incident locations, the states of incident hydrogen exhibit very different characteristics. The adsorption, reflection, and penetration coefficients of incident atoms are accessed. It is found that the incident hydrogen with energy lower than 0.35 eV is 100 percent reflected. When one hydrogen atom is adsorbed to one carbon atom, the bond energy of this carbon with its nearest neighbors is reduced by 1.2 eV from 4.9 eV.
In the second part of this thesis, the collision processes between one hydrogen atom and graphene with single vacancy defect have been investigated. Energy transfers between hydrocarbon particles have been studied during the collision processes at the edge of vacancy defects. Energy losses for C-C and C-H bond also have been studied. The results show:The monovacancy has a big influence on adsorption between hydrocarbon particles; In certain areas of the graphite sheet, an incident hydrogen atom can be reflected backwards in two different energy ranges; hydrocarbon particles, which adsorbed at the monovacancy edge, form a bond in sp2 configuration, without an overhang configuration. However, C-C bond energy does not reduce while previous work found that theirs bond energy decreased byl.2 eV during hydrocarbon bond forming. We also found that, the carbon atom, at the vacancy edge, has more capacity to absorb incident energy, but has less capacity to spread the gained energy. These results will be of great help to understand the chemical erosion and tritium retention in fusion devices.
引文
[1]王淦昌.21世纪主要能源展望[J].核科学与工程,1998,18(2)：97—108.
[2]李云凯,纪康俊.聚变堆等离子体面对材料[J].材料导报,1999,13(3)：3-5.
[3]石秉仁.磁约束聚变原理及实践[M].原子能出版社,1999.
[4]金钟声.受控热核聚变实验装置[M].中国科学技术大学出版社,1999.
[5]S. Yu, Lu'yanov. Diagnostics of a Thermonuclear Plasma [M], Energoatomizdat, Moscow, pp.112-113.1985.
[6]HT-7U物理设计组.HT-7U物理设计文集[M].合肥：中国科学院等离子体物理所,1998.
[7]J. R. Roth,李兴中等译.聚变能引论[M].北京：清华大学出版社,1993.
[8]F. Peterson. Inertial Fusion Energy:A Tutorial on the Technology and Economics, University of California[M]. Berkeley:University of California Press,1998.
[9]等离子体物理科学发展战略研究课题组.核聚变与低温等离子体[M].科学出版社,2004.
[10]I. Smid, M. Aldba, G. Vieider, et al. Development of tungsten armor and bonding to Copper for plasma-interactive components[J]. J. Nucl. Mater.1998,258-263:150-172.
[11]R. Andreani. The European technology fusion program[J]. Fusion Eng. Des.2001,56-57: 5-18.
[12]H. Bolt, V. Barabash, W. Krauss, et al. Materials for the plasma-facing components of fusion reactors[J]. J. Nucl. Mater.2004,329-333:66-73.
[13]K. Ioki, V. Barabash, A. Cardella, et al. Design and material selection for ITER first wall/blanket, divertor and vacuum vessel [J]. J. Nucl. Mater.1998,258-263:74-84.
[14]G. Janeschitz, K. Borrass, G. Federici, et al. The ITER divertor concept [J]. J. Nucl. Mater.1995,220-222:73-88.
[15]R. Tivey, T. Ando, A. Antipenkov, et al. ITER divertor, design issues and research and development [J]. Fusion Eng. Des.1999,46:207-220.
[16]C. Garca-Rosales. Erosion processes in plasma-wall interactions[J]. J. Nucl. Mater. 1994,211:202-214.
[17]T. Hino, F. Hirano, Y. Yamauchi, et al. Hydrogen retention and erosion of carbon tungsten mixed material[J]. Fusion Eng. Des.2000,49-50:213-216.
[18]P. Andrew, D. Brennan, J. Coad, et al. Tritium recycling and retention in JET[J]. J. Nucl. Mater.1999,266-269:153.
[19]R. Neu, R. Dux, A. Geier. Tungsten as a Plasma Facing Material in ASDEX Upgrade[J]. Fusion Eng. Des.2003,65:367-374.
[20]W. Eckstein, C. Garcia-Rosales, J. Roth, et al. Threshold energy for sputtering and its dependence on angle of incidence[J]. Nucl. Instr. Meth.1993, B83:95.
[21]W. Eckstein, J. Roth, G. Eric, et al. Physical and chemical sputtering of multi component sol ids[J]. Fusion Technol.1991,19:2076-2082.
[22]W. Eckstein, J. Bohdanski, J. Roth. Physical Sputtering in Atomic and Plasma Material Interaction Data for Fusion[J]. Nucl. Fusion.1991,16:51.
[23]W. Eckstein. Energy distributions of sputtered particles[J]. Nucl. Instrum. Methods Phys. Res., Sect. B.1986,18:344-348.
[24]M. Peter. Theory of Sputtering. I. Sputtering Yield of Amorphous and Polycrystalline Targets[J]. Phys. Rev.1969,184:383-416.
[25]J. Roth, J. Bohdansky, and W. Ottenberger, Data on low energy light ion sputtering: IPP Report IPP 9-26[R]. Max Planck Institute fur Plasmaphysik, Garching,1979.
[26]J. Roth, Chemical erosion of carbon based materials in fusion devices[J]. J. Nucl. Mater.1999,266-269:51-57.
[27]B.V. Mech, A.A. Haasz, and J. W. Davis. Chemical erosion of pyrolytic graphite by low energy H and D impact[J]. J. Nucl. Mater.1998,255:153-164.
[28]D.W. Brenner,O. A. Shenderova, J. A. Harrison, et al. A second-generation reactive empirical bond order (REBO) potential energy expression for Hydrocarbons[J]. J. Phys.:Condens.Matter.2002,14:783-802.
[29]D. R. Alfonso, S. E. Ulloa, D. W. Brenner. Hydrocarbon Adsorption on a Diamond (100) Stepped Surface[J]. Phys Rev. B.1994,43:4948.
[30]M P. Allen, D J. Tildesley. Computer Simulation of Liquids [M]. Oxford:Clarendon Press,1987.
[31]M. Born, R. Oppenheimer. Zur Quantentheorie der Molekeln[J]. Ann. der Physik.1927,84: 457.
[32]B. J. Alder, T. E. Wainwright, Studies in molecular dynamics. I. General method[J].J. Chem. Phys.1959,31:459-466.
[32]A.Rahman. Correlations in motion of atoms in liquid argon[J]. Phys. Rev,.1964,136:405-411.
[33]A. Rahman, F. H. Stillinger. Molecular dynamics study of liquid Water[J]. J. Chem. Phys.,1971,55:3336-3359.
[34]J. A. McCammon, B. R. Gelin, M. KarPlus. Dynamics of folded Proteins[J]. Nature 1977,267:585 - 590.
[35]H. J. C. Berendsen, J. P. M. Postma, W. F. V. Gunsteren. Molecular dynamics methods with coupling to an external bath[J]. J. Chem. Phys.,1984,8-1:3684-3690.
[36]S. A. Nose. Unified formulation of the constant temperature molecular dynamics methods[J]. J. Chem. Phys.1984,81:5-11.
[37]L.Verlet. Computer'Experiments'on Classical Fluids. I. Thermodynamical Properties of Lennard-Jones Molecules[J]. Phys. Rev.1967,159:98.
[38]R. W. Hockney. Computer Simulation Using Particles[J]. Methods. Comput. Phys. 1970,9:136.
[39]W. C. Swope, H. C. Andersen, P. H. Berens, et al. A computer simulation method for the calculation of equilibrium constants for the formation of physical clusters of molecules:applications to small water clusters[J]. J. Chem. Phys.1982,76:637.
[40]D. C. RaPaPort. The Art of Molecular Dynamics Simulation[M]. New York:Cambridge University Press,2004.
[41]A. F. Voter. Hyperdynamics:Accelerated Molecular Dynamics of Infrequent Events[J]. J. Chem. Phys.1997,06:4665.
[42]潘必才.包含键环境修正的硅氢紧束缚势模型物理学[J].物理学报,2001,50：268-272.
[43]J. Tersoff. New Empirical Model for the structural Properties of Silicon[J]. Phys. Rev. Lett.1984,56:632-635.
[44]D. W. Brenner. Empirical Potential for hydrocarbons for use in simulating the Chemical vapor deposition of diamond films [J]. Phys. RevB.1990,42:9458 - 9471.
[45]Jiang JinWu, Wang JianSheng, Li Baowen. Elastic and nonlinear stiffness of graphene: A simple approach[J]. Phys. Rev. B.2010,81:073405.
[46]D. W. Brenner. The Art and Science of an Analytic Potential [J]. phys. stat. sol. (b). 2000,217:23.
[47]M. T. Yin, Marvin L.Cohen. Will Diamond Transform under Megabar Pressures?[J]. Phys. Rev. Lett.1983,50:2006.
[48]M. T. Yin, Marvin L. Cohen. Structural theory of graphite and graphitic silicon[J]. Phys. Rev. B.1983,29:6996.
[49]Russell D. Johnson III, Computational Chemistry Group, NIST. Computational Chemistry Comparison and Benchmark Datebase[DB/OL].2000. [2000,09,22]. http://srdata. nist. gov/ cccbdb/
[50]R. Tivey, T. Ando, A. Antipenkov, et al. ITER divertor, design issues and research and development[J]. Fusion Eng. Des.1999,46:207-220.
[51]R. Parker, G. Janeschitz, H. D. Pacher, et al. Plasma-wall interactions in ITER[J]. J. Nucl. Mater.1997,241-243:1-26.
[52]G. Janeschitz, K. Borrass, G. Federici, et al. The ITER divertor concept[J]. J. Nucl. Mater.1995,220-222:73-88.
[53]A. P. Zakharov, A. E. Gorodetsky, V. Kh. Alimov, et al. Hydrogen retention in plasma facing materials and its consequences on tokamak operation[J]. J. Nucl. Mater. 1997,241-243:52-67.
[54]H. Atsumi. Hydrogen retention in graphite and carbon materials under a fusion reactor environment[J]. J. Nucl. Mater.2003,313-316:543-547.
[55]R. A. Causey. Hydrogen isotope retention and recycling in fusion reactor plasma-facing components [J]. J. Nucl. Mater.2002,300:91-117.
[56]B. V. Mech, A. A. Haasz, J. W. Davis. Chemical erosion of pyrolytic graphite by low energy H and D'impact[J]. J. Nucl. Mater.1997,241-243:1147-1151.
[57]J. Roth, R. Preuss, W. Bohmeyer, et al. Flux dependence of carbon chemical erosion by deuterium ions[J]. Nucl. Fusion 2004,44:21-25.
[58]A. Sagara, S. Masuzaki, T. Morisaki, et al. Helical divertor operation and erosion/deposition at target surfaces in LHD[J]. J. Nucl. Mater.2003,313-316:1-10.
[59]T. Nakano, H. Kubo, S. Higashijima, et al. Measurement of the chemical sputtering yields of CH(?)/CD4 and C2Hx/C2Dx, at the carbon divertor plates of JT-60U[J]. Nucl. Fusion 2002,42:689-696.
[60]J. H. Liang, M. Mayer, J. Roth, et al. Computer simulation of chemical erosion of graphite due to hydrogen ion bombardment[J]. Nucl. Instrum. Methods Phys. Res. 2003,202:195-200.
[61]E. Salonen, K. Nordlund, J. Tarus, et al. Suppression of carbon erosion by hydrogen shielding during high flux hydrogen bombardment[J]. Phys. Rev. B. 1999,60:14005-14008.
[62]D. A. Alman, D. N. Ruzic. Molecular dynamics calculation of carbon/hydrocarbon reflection coefficients on a hydrogenated graphite surface[J]. J. Nucl. Mater. 2003,313-316:182-186.
[63]E. Salonen, K. Nordlund, J. Keinonen. Swift chemical sputtering of amorphous hydrogenated carbon[J]. Phys. Rev. B.2001,63:195415.
[64]A. Ito, H. Nakamura. Molecular dynamics simulation of collisions between hydrogen and graphite[J]. J. Plasma Physics.2006,72:805-808.
[65]A. Ito, H. Nakamura, A. Takayama. Chemical Reaction between Single Hydrogen Atom and Graphene[J]. Condens. Matter Phys.2008,2:0703377.
[66]A. Ito, H. Nakamura. Molecular Dynamics Simulation of Bombardment of Hydrogen Atoms on Graphite Surface[J]. Commun. Comput. Phys.2008,4:592-610.
[67]A. Ito, H. Nakamura. Hydrogen isotope sputtering of graphite by molecular dynamics simulation[J]. Thin Solid Films.2008,516:6553-6559.
[68]A. Ito, Y. Wang, S. Irle, et al. Molecular dynamics simulation of hydrogen atom sputtering on the surface of graphite with defect and edge[J]. J. Nucl. Mater. 2009,390-391:183-187.
[69]J. P. Biersack, L.G. Haggmark. A Monte Carlo Computer Program For The Transport of Energetic Ions in Amorphous Targets[J]. Nucl. Instrum. Methods.1980:174:257-269.
[70]J. P. Biersack, W. Eckstein. Sputtering Studies with the Monte Carlo Program TRIM. SP[J]. Appl. Phys. A.1984,34:73-94.
[71]W. Moller, W. Eckstein. Tridyn-A Trim Simulation Code Including Dynamic Composition Changes[J]. Nucl. Instrum. Methods Phys. Res., Sect. B2.1984,814-818.
[72]W. Moller, W. Eckstein. Tridyn-Binary Collision Simulation of Atomic Collisions and Dynamic Composition Changes in solids[J]. Comput. Phys. Commun.1988,51:355-368.
[73]J. Lindhard, M. Scharff. Energy Dissipation by Ions in the kev Region [J]. Phys. Rev. 1961,124:128.
[74]R. Yamada. Chemical sputtering yields of graphite[J]. J. Nucl. Mater.1987,145-147: 359-363.
[75]J. W. Davisa, A. A. Haasza, P. C. Stangebya. Hydrocarbon formation due to combined H+ ion and HO atom impact on pyrolytic graphite [J]. J. Nucl. Mater.1988,155-157:234-240.
[76]E. Vietzke, V. Philipps. Hydrocarbon formation on carbon surfaces facing a hydrogen plasma[J]. Fusion Technol.1989,15:108-117.
[77]A. A. Haasz, J. W. Davis. Comparison of the chemical erosion of carbon/carbon composites and pyrolytic graphite[J]. J. Nucl. Mater.1990,175 84-89.
[78]A. Cambe, E. Gauthier, J. Hogan, et al. Chemical sputtering of carbon in Tore-Supra outboard pump limiter[J]. J. Nucl. Mater.2003,313-316:364-369.
[79]Y. Ferroa, F. Marinellia, A. Allouche, et al. Density functional study of chemical erosion mechanisms in carbon and boron-doped carbon as plasma facing material in tokamaks[J]. J. Nucl. Mater.2003,321:294-304.
[80]Sun Jizhong, Li Shouyang, T. Stirner, et al. Molecular dynamics simulation of energy exchanges during hydrogen collision with graphite sheets[J]. J. Appl. Phys. 2010,10:100-107
[2]李云凯,纪康俊.聚变堆等离子体面对材料[J].材料导报,1999,13(3)：3-5.
[3]石秉仁.磁约束聚变原理及实践[M].原子能出版社,1999.
[4]金钟声.受控热核聚变实验装置[M].中国科学技术大学出版社,1999.
[5]S. Yu, Lu'yanov. Diagnostics of a Thermonuclear Plasma [M], Energoatomizdat, Moscow, pp.112-113.1985.
[6]HT-7U物理设计组.HT-7U物理设计文集[M].合肥：中国科学院等离子体物理所,1998.
[7]J. R. Roth,李兴中等译.聚变能引论[M].北京：清华大学出版社,1993.
[8]F. Peterson. Inertial Fusion Energy:A Tutorial on the Technology and Economics, University of California[M]. Berkeley:University of California Press,1998.
[9]等离子体物理科学发展战略研究课题组.核聚变与低温等离子体[M].科学出版社,2004.
[10]I. Smid, M. Aldba, G. Vieider, et al. Development of tungsten armor and bonding to Copper for plasma-interactive components[J]. J. Nucl. Mater.1998,258-263:150-172.
[11]R. Andreani. The European technology fusion program[J]. Fusion Eng. Des.2001,56-57: 5-18.
[12]H. Bolt, V. Barabash, W. Krauss, et al. Materials for the plasma-facing components of fusion reactors[J]. J. Nucl. Mater.2004,329-333:66-73.
[13]K. Ioki, V. Barabash, A. Cardella, et al. Design and material selection for ITER first wall/blanket, divertor and vacuum vessel [J]. J. Nucl. Mater.1998,258-263:74-84.
[14]G. Janeschitz, K. Borrass, G. Federici, et al. The ITER divertor concept [J]. J. Nucl. Mater.1995,220-222:73-88.
[15]R. Tivey, T. Ando, A. Antipenkov, et al. ITER divertor, design issues and research and development [J]. Fusion Eng. Des.1999,46:207-220.
[16]C. Garca-Rosales. Erosion processes in plasma-wall interactions[J]. J. Nucl. Mater. 1994,211:202-214.
[17]T. Hino, F. Hirano, Y. Yamauchi, et al. Hydrogen retention and erosion of carbon tungsten mixed material[J]. Fusion Eng. Des.2000,49-50:213-216.
[18]P. Andrew, D. Brennan, J. Coad, et al. Tritium recycling and retention in JET[J]. J. Nucl. Mater.1999,266-269:153.
[19]R. Neu, R. Dux, A. Geier. Tungsten as a Plasma Facing Material in ASDEX Upgrade[J]. Fusion Eng. Des.2003,65:367-374.
[20]W. Eckstein, C. Garcia-Rosales, J. Roth, et al. Threshold energy for sputtering and its dependence on angle of incidence[J]. Nucl. Instr. Meth.1993, B83:95.
[21]W. Eckstein, J. Roth, G. Eric, et al. Physical and chemical sputtering of multi component sol ids[J]. Fusion Technol.1991,19:2076-2082.
[22]W. Eckstein, J. Bohdanski, J. Roth. Physical Sputtering in Atomic and Plasma Material Interaction Data for Fusion[J]. Nucl. Fusion.1991,16:51.
[23]W. Eckstein. Energy distributions of sputtered particles[J]. Nucl. Instrum. Methods Phys. Res., Sect. B.1986,18:344-348.
[24]M. Peter. Theory of Sputtering. I. Sputtering Yield of Amorphous and Polycrystalline Targets[J]. Phys. Rev.1969,184:383-416.
[25]J. Roth, J. Bohdansky, and W. Ottenberger, Data on low energy light ion sputtering: IPP Report IPP 9-26[R]. Max Planck Institute fur Plasmaphysik, Garching,1979.
[26]J. Roth, Chemical erosion of carbon based materials in fusion devices[J]. J. Nucl. Mater.1999,266-269:51-57.
[27]B.V. Mech, A.A. Haasz, and J. W. Davis. Chemical erosion of pyrolytic graphite by low energy H and D impact[J]. J. Nucl. Mater.1998,255:153-164.
[28]D.W. Brenner,O. A. Shenderova, J. A. Harrison, et al. A second-generation reactive empirical bond order (REBO) potential energy expression for Hydrocarbons[J]. J. Phys.:Condens.Matter.2002,14:783-802.
[29]D. R. Alfonso, S. E. Ulloa, D. W. Brenner. Hydrocarbon Adsorption on a Diamond (100) Stepped Surface[J]. Phys Rev. B.1994,43:4948.
[30]M P. Allen, D J. Tildesley. Computer Simulation of Liquids [M]. Oxford:Clarendon Press,1987.
[31]M. Born, R. Oppenheimer. Zur Quantentheorie der Molekeln[J]. Ann. der Physik.1927,84: 457.
[32]B. J. Alder, T. E. Wainwright, Studies in molecular dynamics. I. General method[J].J. Chem. Phys.1959,31:459-466.
[32]A.Rahman. Correlations in motion of atoms in liquid argon[J]. Phys. Rev,.1964,136:405-411.
[33]A. Rahman, F. H. Stillinger. Molecular dynamics study of liquid Water[J]. J. Chem. Phys.,1971,55:3336-3359.
[34]J. A. McCammon, B. R. Gelin, M. KarPlus. Dynamics of folded Proteins[J]. Nature 1977,267:585 - 590.
[35]H. J. C. Berendsen, J. P. M. Postma, W. F. V. Gunsteren. Molecular dynamics methods with coupling to an external bath[J]. J. Chem. Phys.,1984,8-1:3684-3690.
[36]S. A. Nose. Unified formulation of the constant temperature molecular dynamics methods[J]. J. Chem. Phys.1984,81:5-11.
[37]L.Verlet. Computer'Experiments'on Classical Fluids. I. Thermodynamical Properties of Lennard-Jones Molecules[J]. Phys. Rev.1967,159:98.
[38]R. W. Hockney. Computer Simulation Using Particles[J]. Methods. Comput. Phys. 1970,9:136.
[39]W. C. Swope, H. C. Andersen, P. H. Berens, et al. A computer simulation method for the calculation of equilibrium constants for the formation of physical clusters of molecules:applications to small water clusters[J]. J. Chem. Phys.1982,76:637.
[40]D. C. RaPaPort. The Art of Molecular Dynamics Simulation[M]. New York:Cambridge University Press,2004.
[41]A. F. Voter. Hyperdynamics:Accelerated Molecular Dynamics of Infrequent Events[J]. J. Chem. Phys.1997,06:4665.
[42]潘必才.包含键环境修正的硅氢紧束缚势模型物理学[J].物理学报,2001,50：268-272.
[43]J. Tersoff. New Empirical Model for the structural Properties of Silicon[J]. Phys. Rev. Lett.1984,56:632-635.
[44]D. W. Brenner. Empirical Potential for hydrocarbons for use in simulating the Chemical vapor deposition of diamond films [J]. Phys. RevB.1990,42:9458 - 9471.
[45]Jiang JinWu, Wang JianSheng, Li Baowen. Elastic and nonlinear stiffness of graphene: A simple approach[J]. Phys. Rev. B.2010,81:073405.
[46]D. W. Brenner. The Art and Science of an Analytic Potential [J]. phys. stat. sol. (b). 2000,217:23.
[47]M. T. Yin, Marvin L.Cohen. Will Diamond Transform under Megabar Pressures?[J]. Phys. Rev. Lett.1983,50:2006.
[48]M. T. Yin, Marvin L. Cohen. Structural theory of graphite and graphitic silicon[J]. Phys. Rev. B.1983,29:6996.
[49]Russell D. Johnson III, Computational Chemistry Group, NIST. Computational Chemistry Comparison and Benchmark Datebase[DB/OL].2000. [2000,09,22]. http://srdata. nist. gov/ cccbdb/
[50]R. Tivey, T. Ando, A. Antipenkov, et al. ITER divertor, design issues and research and development[J]. Fusion Eng. Des.1999,46:207-220.
[51]R. Parker, G. Janeschitz, H. D. Pacher, et al. Plasma-wall interactions in ITER[J]. J. Nucl. Mater.1997,241-243:1-26.
[52]G. Janeschitz, K. Borrass, G. Federici, et al. The ITER divertor concept[J]. J. Nucl. Mater.1995,220-222:73-88.
[53]A. P. Zakharov, A. E. Gorodetsky, V. Kh. Alimov, et al. Hydrogen retention in plasma facing materials and its consequences on tokamak operation[J]. J. Nucl. Mater. 1997,241-243:52-67.
[54]H. Atsumi. Hydrogen retention in graphite and carbon materials under a fusion reactor environment[J]. J. Nucl. Mater.2003,313-316:543-547.
[55]R. A. Causey. Hydrogen isotope retention and recycling in fusion reactor plasma-facing components [J]. J. Nucl. Mater.2002,300:91-117.
[56]B. V. Mech, A. A. Haasz, J. W. Davis. Chemical erosion of pyrolytic graphite by low energy H and D'impact[J]. J. Nucl. Mater.1997,241-243:1147-1151.
[57]J. Roth, R. Preuss, W. Bohmeyer, et al. Flux dependence of carbon chemical erosion by deuterium ions[J]. Nucl. Fusion 2004,44:21-25.
[58]A. Sagara, S. Masuzaki, T. Morisaki, et al. Helical divertor operation and erosion/deposition at target surfaces in LHD[J]. J. Nucl. Mater.2003,313-316:1-10.
[59]T. Nakano, H. Kubo, S. Higashijima, et al. Measurement of the chemical sputtering yields of CH(?)/CD4 and C2Hx/C2Dx, at the carbon divertor plates of JT-60U[J]. Nucl. Fusion 2002,42:689-696.
[60]J. H. Liang, M. Mayer, J. Roth, et al. Computer simulation of chemical erosion of graphite due to hydrogen ion bombardment[J]. Nucl. Instrum. Methods Phys. Res. 2003,202:195-200.
[61]E. Salonen, K. Nordlund, J. Tarus, et al. Suppression of carbon erosion by hydrogen shielding during high flux hydrogen bombardment[J]. Phys. Rev. B. 1999,60:14005-14008.
[62]D. A. Alman, D. N. Ruzic. Molecular dynamics calculation of carbon/hydrocarbon reflection coefficients on a hydrogenated graphite surface[J]. J. Nucl. Mater. 2003,313-316:182-186.
[63]E. Salonen, K. Nordlund, J. Keinonen. Swift chemical sputtering of amorphous hydrogenated carbon[J]. Phys. Rev. B.2001,63:195415.
[64]A. Ito, H. Nakamura. Molecular dynamics simulation of collisions between hydrogen and graphite[J]. J. Plasma Physics.2006,72:805-808.
[65]A. Ito, H. Nakamura, A. Takayama. Chemical Reaction between Single Hydrogen Atom and Graphene[J]. Condens. Matter Phys.2008,2:0703377.
[66]A. Ito, H. Nakamura. Molecular Dynamics Simulation of Bombardment of Hydrogen Atoms on Graphite Surface[J]. Commun. Comput. Phys.2008,4:592-610.
[67]A. Ito, H. Nakamura. Hydrogen isotope sputtering of graphite by molecular dynamics simulation[J]. Thin Solid Films.2008,516:6553-6559.
[68]A. Ito, Y. Wang, S. Irle, et al. Molecular dynamics simulation of hydrogen atom sputtering on the surface of graphite with defect and edge[J]. J. Nucl. Mater. 2009,390-391:183-187.
[69]J. P. Biersack, L.G. Haggmark. A Monte Carlo Computer Program For The Transport of Energetic Ions in Amorphous Targets[J]. Nucl. Instrum. Methods.1980:174:257-269.
[70]J. P. Biersack, W. Eckstein. Sputtering Studies with the Monte Carlo Program TRIM. SP[J]. Appl. Phys. A.1984,34:73-94.
[71]W. Moller, W. Eckstein. Tridyn-A Trim Simulation Code Including Dynamic Composition Changes[J]. Nucl. Instrum. Methods Phys. Res., Sect. B2.1984,814-818.
[72]W. Moller, W. Eckstein. Tridyn-Binary Collision Simulation of Atomic Collisions and Dynamic Composition Changes in solids[J]. Comput. Phys. Commun.1988,51:355-368.
[73]J. Lindhard, M. Scharff. Energy Dissipation by Ions in the kev Region [J]. Phys. Rev. 1961,124:128.
[74]R. Yamada. Chemical sputtering yields of graphite[J]. J. Nucl. Mater.1987,145-147: 359-363.
[75]J. W. Davisa, A. A. Haasza, P. C. Stangebya. Hydrocarbon formation due to combined H+ ion and HO atom impact on pyrolytic graphite [J]. J. Nucl. Mater.1988,155-157:234-240.
[76]E. Vietzke, V. Philipps. Hydrocarbon formation on carbon surfaces facing a hydrogen plasma[J]. Fusion Technol.1989,15:108-117.
[77]A. A. Haasz, J. W. Davis. Comparison of the chemical erosion of carbon/carbon composites and pyrolytic graphite[J]. J. Nucl. Mater.1990,175 84-89.
[78]A. Cambe, E. Gauthier, J. Hogan, et al. Chemical sputtering of carbon in Tore-Supra outboard pump limiter[J]. J. Nucl. Mater.2003,313-316:364-369.
[79]Y. Ferroa, F. Marinellia, A. Allouche, et al. Density functional study of chemical erosion mechanisms in carbon and boron-doped carbon as plasma facing material in tokamaks[J]. J. Nucl. Mater.2003,321:294-304.
[80]Sun Jizhong, Li Shouyang, T. Stirner, et al. Molecular dynamics simulation of energy exchanges during hydrogen collision with graphite sheets[J]. J. Appl. Phys. 2010,10:100-107