共查询到18条相似文献,搜索用时 156 毫秒
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基于嵌入原子势考察体心立方(bcc)金属Ta的广义层错能和广义孪晶能并获得广义层错能和广义孪晶能曲线. 研究表明,bcc Ta的广义层错能曲线与面心立方金属的广义层错能曲线有明显差异,Ta的广义层错能曲线不存在明显的能量极小值,位错主要以全位错的形式发射. 不同原子厚度的广义孪晶能曲线表明4个原子层的孪晶能曲线开始出现亚稳定的能量极小值,5个原子层的孪晶能曲线出现稳定的能量极小值. 为进一步验证广义层错能和广义孪晶能曲线揭示的塑性变形机理,采用准连续介质力学多尺度方法研究Ⅱ型裂纹尖端的初始塑性变形过程.
关键词:
广义层错能
广义孪晶能
体心立方金属钽
Ⅱ型裂纹 相似文献
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用分子动力学方法研究了端口接枝不同数量羟基对扶手椅型和锯齿型单壁碳纳米管弹性模量的影响.结果表明,未接枝的扶手椅型(5, 5),(10,10)管和锯齿型(9, 0),(18, 0)管杨氏模量分别为948,901和804,860GPa.在接枝2—8个羟基情况下,锯齿型单壁碳纳米管拉伸杨氏模量基本不随接枝数量增加发生变化,而扶手椅单壁碳纳米管则不同,接枝状态下的弹性模量比未接枝状态小很多,但接枝一定数量后,其杨氏模量又略增到某一稳定值.分别从接枝后碳纳米管变形电子密度等值线结构、C—C键长和系统结合能变化规律等方面,对单壁碳纳米管弹性模量的接枝效应进行了分析.
关键词:
碳纳米管
羟基
接枝效应
杨氏模量 相似文献
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从能带理论出发,采用电子紧束缚能量色散关系,推导锯齿,扶手椅和手性单壁碳纳米管(SWCNT)的电子能带结构表达式,指出单壁碳纳米管或为金属或为半导体的判据。结果表示:单壁碳纳米管的电子结构与其几何结构密切相关,如扶手椅型单壁碳纳米管是金属性的,而对其它类型的单壁碳纳米管是与碳纳米管的手性指数有关,只有手性指数n和m的差别等于3的倍数时,单壁碳纳米管是金属性的,否则会显出有带隙的半导体特性。这意味着单壁碳纳米管是由特殊的电子传输和光学性质,在纳米电子学领域具有巨大的潜在应用价值。 相似文献
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运用分子动力学方法具体模拟研究单个碳纳米管(CNTs)在加热过程中的结构变化.选择多组不同结构的单壁碳纳米管(SWCNTs)和双壁碳纳米管(DWCNTs)作为研究对象,加热温度从室温开始到4000 K,压强保持为1 atm.结果表明单壁碳管中手性型结构热稳定性最好,其次是扶手椅型和锯齿型,当手性角相同时,直径大的热稳定性更高;对于双壁碳管,研究表明当双壁中至少之一为手性结构时其热稳定好,而内外壁均为锯齿结构的稳定性最差,该结果进一步支持了有关单壁碳管的结论;还从理论上探索了描述结构热稳定性的方式,并在键层
关键词:
单壁碳纳米管
双壁碳纳米管
分子动力学方法
热稳定性能 相似文献
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利用计入卷曲效应的单壁碳纳米管(SWCNT)的能量色散关系,计算最低导带的电子速度及有效质量,并与不计入卷曲效应的结果进行了比较.计算结果表明:卷曲效应对电子速度及有效质量的影响与SWCNT的类型密切相关,金属锯齿型SWCNT对卷曲效应最为敏感,其次是扶手椅型SWCNT,最不敏感的是半导体锯齿型SWCNT.由此可以推断,卷曲效应对金属锯齿型SWCNT电子结构及低偏压输运特性影响最大,其次是扶手椅型SWCNT,影响最不明显的是半导体锯齿型SWCNT.这些结果与实验测量及密度泛函理论计算结果完全一致.
关键词:
单壁碳纳米管
卷曲效应
电子速度
电子有效质量 相似文献
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利用紧束缚势分子动力学模拟方法,研究了温度在1000 K-3000 K之间单壁碳纳米管端口结构的变化趋势.计算表明,温度对整个管端口结构有重要影响,温度升高容易使理想单壁碳管端口封闭.温度在3000 K下碳管端口达到封闭,而且端口封闭导致碳管系统能量的降低.碳纳米管长度越长,端口封闭越快,且扶手型碳纳米管比锯齿型碳纳米管更容易形成端口封闭的结构. 相似文献
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用分子动力学方法研究了N,O,Si,P,S等5种杂质对扶手椅型(5,5)和锯齿型(9,0)单壁碳纳米管杨氏模量的影响.结果表明:直径为0.678和0.704 nm的扶手椅型(5,5)和锯齿型(9,0)碳纳米管在无掺杂时其杨氏模量分别为948和804 GPa.在掺杂浓度10%以下,碳纳米管的拉伸杨氏模量均随掺杂浓度增加近似呈线性下降规律,下降率以Si掺杂最大,N掺杂最小.对与C同周期的元素掺杂,随原子序数增加碳纳米管的杨氏模量下降率增大;与C不同周期的元素掺杂,碳纳米管的杨氏模量随掺杂浓度增加下降率更大,但
关键词:
碳纳米管
杂质
杨氏模量
分子动力学方法 相似文献
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Effects of Radius and Orientation of Single-Walled Carbon Nanotubes on Their Nonlinear Tensile Deformation Behaviour 下载免费PDF全文
By capturing the atomic information and reflecting the behaviour governed by a nonlinear potential function, an analytical molecular mechanics approach is applied to establish the constitutive relation for single-walled carbon nanotubes (SWCNTs). The nonlinear tensile deformation curves of zigzag and armchair nanotubes with different radii are predicted, and the elastic properties of these SWCNTs are obtained. A conclusion is made that the nanotube radius has little effect on the mechanical behaviour of SWCNTs subject to simple tension, while the nanotube orientation has larger influence. 相似文献
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The calculation of energy gaps in small single-walled carbon nanotubes within a symmetry-adapted tight-binding model 下载免费PDF全文
This paper studies in detail the electronic properties of the semimetallic single-walled carbon nanotubes by applying the symmetry-adapted tight-binding model.It is found that the hybridization of π-σ states caused by the curvature produces an energy gap at the vicinity of the Fermi level.Such effects are obvious for the small zigzag and chiral single-walled carbon nanotubes.The energy gaps decrease as the diameters and the chiral angles of the tubes increase,while the top of the valence band and the bottom of the conduction band of armchair tubes cross at the Fermi level.The numeral results agree well with the experimental results. 相似文献
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Electronic properties of multi-defected zigzag single-walled carbon nanotubes are investigated by use of the tight-binding Green's function method. The Stone-Wales defects and the vacancies are considered. We find that the conductance sensitively depends on the realistic defect configurations for the metallic zigzag carbon nanotubes. Interestingly, the electronic transport properties of the nanotubes with three vacancies can be considered as the sum effect of two double-vacancies, while those with Stone-Wal... 相似文献
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The total carbo-mer of single-walled carbon nanotubes (C-SWCNTs) are constructed by inserting two sp carbon atoms into each C-C bond in pristine single-walled carbon nanotubes (SWCNTs). The geometric, mechanical and electronic properties for these novel structures are investigated by self-consistent-field crystal calculations. The calculated zigzag and chiral C-SWCNTs are all small gap semiconductors, whereas the metallic property is still kept in the armchair C-SWCNT. The calculated Young's moduli of C-SWCNTs are smaller than those of SWCNTs. Our calculations show that the zigzag C-SWCNTs have higher mobility than the corresponding SWCNTs. Moreover, the calculated mobility of the C-SWCNTs has a periodic change with the change of the tube diameters. 相似文献