曲率对Rh在锯齿型单壁碳纳米管内外吸附影响的研究

利用密度泛函理论系统的研究了单壁碳纳米管的曲率对Rh原子在锯齿型碳管内外的吸附行为, 发现Rh原子在管外吸附比管内稳定; 随着碳管管径的增加, 曲率减小, 管内外吸附能的差值逐渐减小, 接近Rh原子在石墨烯上的吸附能. 电荷密度分析表明, 由于卷曲效应使碳纳米管管外的电荷密度大于管内, 随着曲率减小, 这种差别逐渐减小. 管内外吸附Rh原子的Bader电荷差值及局域态密度差别亦随着曲率的下降而减小, 这与Rh原子在管内外吸附能的变化规律相一致.     

曲率对Rh在锯齿型单壁碳纳米管内外吸附影响的研究

利用密度泛函理论系统的研究了单壁碳纳米管的曲率对Rh原子在锯齿型碳管内外吸附行为的影响,发现Rh原子在管外吸附比管内稳定;随着碳管管径的增加,曲率减小,管内外吸附能的差值逐渐减小,接近Rh原子在石墨烯上的吸附能.电荷密度分析表明,由于卷曲效应使碳纳米管管外的电荷密度大于管内,随着曲率减小,这种差别逐渐减小.管内外吸附R...     

卷曲方式对Rh原子在单壁碳纳米管内外吸附的影响

碳纳米管曲率与卷曲方式是同时存在并影响金属原子在碳纳米管内外吸附行为的重要因素, 单独研究卷曲方式对金属吸附行为的影响较困难. 选取曲率相近、卷曲方式不同的扶手椅型(6, 6)、锯齿型(10, 0)与手性(8, 4)单壁碳纳米管(SWCNT), 利用密度泛函理论研究了Rh原子在SWCNT内外的吸附行为. 构型优化表明:由于SWCNT卷曲方式不同, 导致Rh原子在(6, 6),(10, 0)与(8, 4)SWCNT内外吸附的稳定构型不同; 不同卷曲方式亦使SWCNT与Rh原子相互作用的C原子不同, 导致Rh 关键词： 密度泛函理论 单壁碳纳米管 Rh原子 卷曲方式     

硼原子掺杂对碳纳米管吸附Ne原子影响的第一性原理计算

采用基于第一性原理的密度泛函理论(DFT)和局域密度近似(LDA)方法,优化计算得到碳纳米管(CNT),硼原子取代碳原子及其吸附氖原子前后系统的几何结构,能量,电子能带和态密度.结果显示,碳纳米管的能带结构与石墨的层状几何结构相似,能量的变化只在kz=0和kz=0.5平面之间沿着c轴方向出现.B原子取代C原子使价带和导带分别分裂为两个和三个能带.对Ne原子的吸附使价带能量沿着c轴方向升高并导致Fermi面附近的态密度下降.Ne原子的吸附在谷位H最稳定,顶位A其次.C-C间σ键的弯曲使Ne原子吸附在桥位b1比桥位b2处更为稳定.Ne原子在管外的吸附均为放热过程,而管内则为吸热过程.结构分析表明Ne原子对C原子有排斥作用,对B原子却具有吸引作用.B原子取代C原子的位置略凸出于CNT的管壁之外,使Ne原子的吸附能增加.     

N2H4在NiFe(111)合金表面吸附稳定性和电子结构的第一性原理研究

采用基于色散校正的密度泛函理论进行了第一性原理研究, 详细分析了肼(N₂H₄)在Ni₈Fe₈/Ni(111)合金表面稳定吸附构型的吸附稳定性和电子结构及成键性质. 通过比较发现, 肼分子以桥接方式吸附在表面的两个Fe原子上是最稳定的吸附构型, 其吸附能为-1.578 eV/N₂H₄. 同时发现, 肼分子在这一表面上吸附稳定性的趋势为: 桥位比顶位吸附更有利, 且在Fe原子上比在Ni原子上的吸附作用更强. 进一步分析了不同吸附位点上稳定吸附构型的电子结构、电荷密度转移以及电子局域化情况. 结果发现: 相同吸附位点的电子态密度图基本一致, 并且N原子的p轨道和与之相互作用的表面原子的d轨道之间存在态密度上的重叠; 吸附后电荷密度则主要从肼分子转移到表面原子之上; 在电子局域化函数切面图中也发现吸附后电子被局域到肼分子的N原子和相邻的表面原子之间. 这些电子结构的表征都充分说明肼分子与表面原子之间通过电荷转移形成了强烈的配位共价作用.     

硼原子掺杂对碳纳米管吸附Ne原子影响的第一性原理计算

采用基于第一性原理的密度泛函理论（DFT）和局域密度近似（LDA）方法,优化计算得到碳纳米管（CNT）,硼原子取代碳原子及其吸附氖原子前后系统的几何结构,能量,电子能带和态密度。结果显示,碳纳米管的能带结构与石墨的层状几何结构相似,能量的变化只在kz=0和kz=0.5平面之间沿着c轴方向出现。B原子取代C原子使价带和导带分别分裂为两个和三个能带。对Ne原子的吸附使价带能量沿着c轴方向升高并导致Fermi面附近的态密度下降。Ne原子的吸附在谷位H最稳定,顶位A其次。C-C间σ键的弯曲使Ne原子吸附在桥位b1比桥位b2处更为稳定。Ne原子在管外的吸附均为放热过程,而管内则为吸热过程。结构分析表明Ne原子对C原子有排斥作用,对B原子却具有吸引作用。B原子取代C原子的位置略凸出于CNT的管壁之外,使Ne原子的吸附能增加。     

硼原子掺杂对碳纳米管吸附Ne原子影响的第一性原理计算

采用基于第一性原理的密度泛函理论（DFT）和局域密度近似（LDA）方法，优化计算得到碳纳米管（CNT），硼原子取代碳原子及其吸附氖原子前后系统的几何结构，能量，电子能带和态密度。结果显示，碳纳米管的能带结构与石墨的层状几何结构相似，能量的变化只在kz=0和kz=0.5平面之间沿着c轴方向出现。B原子取代C原子使价带和导带分别分裂为两个和三个能带。对Ne原子的吸附使价带能量沿着c轴方向升高并导致Fermi面附近的态密度下降。Ne原子的吸附在谷位H最稳定，顶位A其次。C-C间σ键的弯曲使Ne原子吸附在桥位b1比桥位b2处更为稳定。Ne原子在管外的吸附均为放热过程，而管内则为吸热过程。结构分析表明Ne原子对C原子有排斥作用，对B原子却具有吸引作用。B原子取代C原子的位置略凸出于CNT的管壁之外，使Ne原子的吸附能增加。     

缺陷碳纳米管限域金属Ti原子的理论研究

基于密度泛函第一性原理研究了金属原子Ti在原始、单空位缺陷(SV)、Stone-Wales(SW)缺陷碳纳米管内外的吸附情况.我们的计算结果表明金属Ti原子在缺陷碳纳米管内外结合能的排列顺序为:SVSW-zSW-xpristine(外吸附),SVSW-xSW-zpristine(内吸附).同时,我们通过吸附结构、电子密度和态密度等分析了Ti原子与碳纳米管的作用机制.其中,SV缺陷碳纳米管由于失去一个碳原子而形成了的三个悬键具有很强的结合能力,金属原子Ti在SV缺陷碳纳米管内外的吸附能力都是最强的.对于SW缺陷的碳纳米管,由于缺陷的位置不同,对于金属原子Ti内外吸附的能力也是不同的.因此,缺陷的存在能调节碳纳米管载体对Ti原子的吸附性能.     

嵌入锂原子的zigzag型单壁碳纳米管的电子传导特性

运用基于第一性原理的密度泛函理论（DFT）的非平衡格林函数（NEGF）方法对Li原子嵌入后的zigzag型单壁碳纳米管(SWCNT)的电子输运性质进行了研究.在构建和优化了Li原子嵌入的zigzag型单壁碳纳米管的电子输运模型后,研究了该系统的电子传输概率、能态密度、电子透射谱,还研究了电子能量和偏置电压设置与变化对其电子输运特性的影响.结果显示zigzag型单壁碳纳米管嵌入Li原子后,电子输运特性发生了较大变化,具有电子输运拓宽效应和量子台阶复苏效应. 关键词： Li原子 碳纳米管 电子输运 拓宽效应     

碳纳米管吸附铜原子的密度泛函理论研究

采用密度泛函方法对铜原子在有限长（5,5）椅型单壁碳纳米管的吸附行为进行了研究.计算结果表明,铜原子吸附在管外壁要比吸附在管内壁能量上更为有利,在管外壁碳原子顶位吸附最佳,属于明显的化学吸附.且用前线轨道理论对其成键特性进行了分析,表明在顶位吸附时主要由铜原子的4s轨道电子与碳纳米管中耦合的σ-π键形成新的σ键.此外还对比计算了两种典型位置电子密度,发现顶位吸附的成键中有更大的电子云重叠.进一步表明在某些情况下铜碳原子可以成键. 关键词： 碳纳米管 铜原子 成键特性     

Structural, curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube

This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.     

Study on the electronic structure and hydrogen adsorption by transition metal decorated single wall carbon nanotubes

The ground state geometry and electronic structure of various 4d transition metal (TM) atom (Y, Zr, Nb and Mo) decorated single wall carbon nanotubes (SWCNTs) are obtained using density functional theory and the projector augmented wave (PAW) method. We found a systematic change in the adsorption site of the transition metal atom with increasing number of d electrons. We also predicted that Y and Zr decorated SWCNTs are metallic whereas Nb and Mo decorated SWCNTs are semiconducting. From detailed electronic structure and Bader charge analysis we found that the systematic variation of the adsorption site with the number of d electrons is related to the decreasing amount of charge transfer from the TM atom to the SWCNT along the 4d series. We have also studied the hydrogen adsorption capabilities of these decorated SWCNTs to understand the role of transition metal d electrons in binding the hydrogen molecules to the system. We found that metallic SWCNT + TM systems are better hydrogen adsorbers. We showed that the hydrogen adsorption by a TM decorated SWCNT will be maximum when all the adsorptions are physisorption and that the retention of magnetism by the system is crucial for physisorption.     

H2在Li掺杂Al6Si+上吸附的理论研究

本文利用密度泛函理论的B3LYP/6-31G(d, p)和组态相互作用的QCISD/6-31G(d, p)研究了Al6Si+和Al6SiLi+团簇的几何和电子结构及其对H2分子的吸附,两种不同方法计算的H2分子在团簇上的吸附能非常一致。H2分子在Al6Si+团簇上的吸附能仅为-0.018 eV,Al6Si+团簇中掺杂Li原子可以明显增强其对H2分子的吸附。Al6SiLi+团簇吸附一个H2分子的吸附能可以达到-0.157 eV,吸附五个H2分子的平均吸附能为-0.088 eV。态密度和自然键轨道分析表明,电荷从Li原子向Si原子转移,H2分子在带正电的Li离子产生的电场中发生极化,从而在静电相互作用下吸附在Li原子周围。     

First principles study of Eu doped carbon nanotubes

The geometric and electronic structures of Eu doped single-walled carbon nanotubes (SWCNTs) have been studied using density functional theory. Three different doping configurations are considered. All of these configurations are stable upon relaxation, and Eu atom on the top of the inside hole site is the most favorable configuration for most nanotubes, except (3,3) CNT. The formation energies vary regularly with the same trend as in the Co and Fe doped cases. The electronic structures studies indicate that the charge transfer basically occurs between 5d6s of Eu and the antibonding orbital of the C6 ring of the SWCNT. Eu atom is monovalent for the exohedral and substitutional doping, and for the endohedral doping of large radius nanotubes; it is bivalent for endohedral doping of (3,3) tube. As the radius increases, the net charges on Eu atom steadily decrease for exohedral and endohedral doping. The magnetic moments of Eu atoms are preserved in all of the configurations, but they vary with the radius of nanotube and adsorbing sites.     

B（N）掺杂单壁碳纳米管的Al原子吸附性能的第一性原理研究

采用基于密度泛函理论的平面波赝势方法和广义梯度近似,对未掺杂、掺B、掺N的碳纳米管(CNT)不同位置上Al原子的吸附进行了几何优化,计算了吸附Al、掺杂前后CNT的能带结构、态密度、差分电荷密度、电荷布居数和吸附能.计算结果表明,掺B使CNT形成缺电子状态,利于具有自由电子的Al原子的吸附结合,可显著提高Al在金属性的(5,5)CNT和半导性的(8,0)CNT外壁的吸附能;掺杂N形成多电子状态,在费米能级附近半满的施主能级也利于填充Al的价电子,改善Al在(5,5)CNT和(8,0)CNT外壁的吸附结合性 关键词： 密度泛函理论 单壁碳纳米管 B(N)掺杂 Al原子吸附     

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule：ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes (SWCNTs) is investigated by density functional theory calculations. Adsorption energies and equilibrium distances are evaluated, and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared. We also investigated the role of the structural defects on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the larger diameters semiconducting CNTs, while the story is paradoxical for the metallic CNTs. The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles. Finally, the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon, hexagon, and heptagon sites in the tube surface. We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs. The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption. Consequently, one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.     

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule: ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes(SWCNTs)is investigated by density functional theory calculations.Adsorption energies and equilibrium distances are evaluated,and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared.We also investigated the role of the structural defects on the adsorption capability of the SWCNTs.We could observe larger adsorption energies for the larger diameters semiconducting CNTs,while the story is paradoxical for the metallic CNTs.The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles.Finally,the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon,hexagon,and heptagon sites in the tube surface.We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs.The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption.Consequently,one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.     

Theoretical investigation of CO adsorption on TM-doped (MgO)12 (TM = Ni, Pd, Pt) nanotubes

CO adsorption on TM-doped magnesia nanotubes (TM = Ni, Pd and Pt) have been studied by using density functional theory. Our calculation results show that CO favors adsorption on TM-doped magnesia nanotubes in the form of C atom bonding with TM atom. Fukui indices analysis clearly exhibits that doping of impurity TM atom allows for a noticeably enhancement of nucleophilic reactivity ability of magnesia nanotube. The adsorption energies demonstrate that CO molecule is more strongly bound on the 3-fold TM atoms than the 4-fold TM atoms. This finding is well confirmed by TM-C bond length, charge transfer and C-O vibrational frequency. The high adsorption energy of 2.55 eV is found when CO adsorbs on 3-fold Pt in Pt-doped magnesia nanotubes, implying the kind of the doping TM atom has a significant influence on the chemical reactivity.