拉压变形对B(N)掺杂碳纳米管Al吸附性能的影响

为了研究(5,5)碳纳米管的B(N)环状掺杂效应,以及拉压变形对B(N)环状掺杂碳纳米管Al吸附性能的影响,采用基于密度泛函理论的平面波赝势和广义梯度近似方法,对B(N)环状掺杂碳纳米管Al吸附模型进行了几何优化,计算了B(N)环状掺杂碳纳米管的形成能,并确定了Al原子的最稳定吸附位置.结果表明,B(N)环状掺杂(5,5)碳纳米管的结构较为稳定.B(N)环状掺杂可以增加碳纳米管与Al之间的吸附能;一定范围内的拉伸和压缩变形则会降低碳纳米管与Al之间的大部分吸附能.     

Li在B掺杂石墨烯表面的吸附和扩散行为

基于密度泛函理论的第一性原理,研究Li在不同B掺杂量的石墨烯表面的吸附和扩散行为。结果表明,Li在3.12%(原子数分数)B掺杂石墨烯表面具有较大的吸附能(Ead),约2.548 e V,是Li在未掺杂石墨烯表面吸附能(1.126 e V)的2.3倍;B掺杂后,导致石墨烯费米能级下移至价带,石墨烯呈现缺电子性,有利于Li的吸附;Li在2.00%(原子数分数)B掺杂石墨烯表面扩散的最小扩散能垒较小,约0.250 e V,略高于Li在石墨烯表面的扩散能垒(0.248 e V)。     

改性石墨烯纳米材料气敏特性的理论研究

利用基于密度泛函理论的第一性原理计算方法,研究单个CO和O2气体分子在多种金属原子修饰的石墨烯表面的吸附作用.结果表明,空位缺陷结构的石墨烯能够显著提高金属原子的稳定性,失去部分电荷的金属原子有助于调控气体分子的吸附特性.对比发现,单个金属Al和Mo原子掺杂的石墨烯体系对O2分子具有极高的灵敏性和选择性.通过不同气体分子的吸附能够调控石墨烯体系的电子结构和磁性.研究结果测试了不同金属原子修饰石墨烯表面的反应活性,为设计新型金属-石墨烯功能器件提供参考.     

Co、Ni-锯齿型石墨烯纳米带体系的磁性与电子结构研究

采用自旋极化的密度泛函理论计算方法研究Co、Ni吸附的锯齿型石墨烯纳米带（n=6,8,10）的几何构型、电子结构与磁性。在真空环境里,吸附过渡金属面后,锯齿型石墨烯纳米带发生弯曲,金属面大多不平整,且在n=8,10的锯齿型石墨烯纳米带上Co、Ni原子倾向于团聚成立体团簇。所有的Co、Ni-锯齿型石墨烯纳米带体系都是金属性的。计算结果表明,石墨烯纳米带的类一维性和边界形状将影响多个金属原子吸附后的堆积构型,同时锯齿型石墨烯纳米带作为吸附底物使吸附的过渡金属产生与无基底支持的二维、三维金属体系和石墨基底上吸附的过渡金属不同的磁性。     

锂离子掺杂聚并吡啶对其电子性质的影响

用量子化学MNDO和EHMO-CO方法研究锂离子(Li^ )对聚并吡啶(PPyPy)的掺杂行为及其对体系电子性质的影响．结果表明：LI^ 可吸附在PPyPy表面的不同位置，洞位是最稳定吸附点．LI^ 掺杂比例不同，体系能隙变化较大，即LI^ 的掺杂对体系的电子性质有较大影响。     

高岭土掺杂NASICON固体电解质及全固态电池性能

针对LiTi2(PO4)3基固态电解质电导率低的问题,采用浙江三门高岭土矿作为主要原料,以高温固相法制备铝、镁、硅共掺杂钠超离子导体(NASICON)型快离子导体Li1+2x+2yAlxMgyTi2-x-ySixP3-xO12.研究掺杂比例、温度对固态电解质离子电导率的影响.结果表明,组成为Li1.8Al0.1Mg0.3Ti1.6Si0.1P2.9O12固体电解质在423 K时有最高离子电导率7.86×10-4 S·cm-1.以该组成固态电解质为基片,喷雾热解原位制备Al/ Li1+xV3O8/ Li1.8Al0.1Mg0.3Ti1.6Si0.1 P2.9O12 /C全固态电池并在1.8～3.9 V电压区间进行50次充放电测试.该电池具有较好的稳定性及循环容量保持能力.30次循环以后放电容量基本稳定在190～205 mAh·g-1之间,充放电效率大于90%.     

F覆盖度对石墨烯体系电子结构和光学性能的影响

为了研究不同F覆盖度下石墨烯吸附体系的电子结构和光学性能,采用第一性原理对本征石墨烯和石墨烯吸附体系进行了几何优化,计算并分析了各体系的吸附能、能带结构、电子态密度、光吸收系数与反射率.结果表明,F原子稳定吸附在石墨烯的顶位,当F覆盖度为6.2%时,体系吸附能最大.F原子的吸附打开了石墨烯的能隙,使其由半金属型转变为半导体型.当F覆盖度为3.1%时,体系能隙值最大.与本征石墨烯相比,石墨烯吸附体系在费米能级处的电子态密度值增大,当F覆盖度为9.4%时,可以获得最大态密度值.石墨烯吸附体系的光吸收系数和反射率峰值相比本征石墨烯均明显减小,且F覆盖度越大,峰值减小程度越显著.在一定波长范围内吸附体系的吸收系数和反射率均出现蓝移现象.     

Bi4Ti3O12陶瓷及其A和B位掺杂的介电研究

测量了Bi4Ti3O12(BTO)陶瓷及其A和B位掺杂的系列材料介电损耗。在温度损耗谱上观察到一损耗峰，通过氧处理和内耗等相关实验手段，证实该峰（PI）是与氧空位有关的弛豫峰。同时观察该峰随不同掺杂类型的变化，分析了BTO陶瓷B位掺杂对铁电性的影响。     

稀土元素Gd掺杂GaN的电子结构和磁学性质研究

采用基于密度泛函理论(DFT)结合投影缀加平面波(PAW)的方法,通过VASP软件包计算研究了稀土元素Gd掺杂GaN的晶格参数、形成能、电子态密度、能带结构和磁学性质.计算过程中将稀土元素Gd的4f电子计入价电子,采用LSDA+U方法处理4f电子的强关联效应.计算结果表明:Gd原子之间的耦合是反铁磁性的,当有足够的空穴载流子存在时能够稳定铁磁相;Ga空位虽然能够提供空穴稳定铁磁相,但是由于在p型GaN中Ga空位的形成能较高而难以形成;而间隙N缺陷和间隙O缺陷的形成能较低,能够稳定GaN∶Gd体系的铁磁相并且能够分别引入1μB和2μB的磁矩,因此认为间隙N和O可能是巨大磁矩的来源.     

高氯酸根在聚并吡啶表面的吸附行为对导电性能的影响

用量子化学ＭＮＤＯ、ＣＮＤＯ／２和ＥＨＭＯ－ＣＯ方法研究高氯酸根（ＣｌＯ＾－４）在聚并吡啶表面的吸附行为以及对聚合物能带结构的影响,结果表明：ＣｌＯ＾－４可吸附在聚并吡啶表面的不同位置,洞位为最稳定吸附点,ＣｌＯ＾－４在大多数位置的吸附使体系的能隙变窄,Ｔ３位减小最多,ＣｌＯ＾－４掺杂聚并吡啶有利于导电性能的提高。     

锂离子掺杂聚并苯对其电子性质的影响

采用量子化学ＭＮＤＯ、ＣＮＤＯ／２方法,对锂离子掺杂有机导体聚并苯从理论上进行探讨,找出Ｌｉ＾＋在聚并苯分子表面的稳定吸附位,ＥＨＭＯ－ＣＯ能带结构计算表明：Ｌｉ＾＋吸附在聚并苯表面不同位置后,在多数情况体系的能隙略有增大,而在洞位时,能隙略减小,有利于导电性的提高。作为电极,洞位是Ｌｉ＾＋吸附与脱附的最佳位置。     

Study on hydrogen atom adsorption and diffusion properties on Mg (0001) surface

Hydrogen atom adsorption and diffusion properties on clean and vacancy defective Mg (0001) surface have been investigated systematically by using a first-principles calculations method based on the density functional theory. The calculation results of adsorption energy and diffusion energy barrier show that hydrogen atom is apt to be adsorbed at fcc and hcp sites on clean Mg (0001) surface, and fcc adsorption site is found to be more preferred. The highest diffusion energy barrier is estimated as 0.6784 eV for the diffusion of hydrogen from clean Mg (0001) surface into its bulk. Surface effects, which affect hydrogen diffusion obviously, results in a slow diffusion velocity of hydrogen from surface to subsurface, while a fast one from subsurface to bulk, indicating the range of surface effects is only restricted within two topmost layers of Mg (0001) surface. Comparatively, Mg atom vacancy on Mg (0001) surface not only enhances the chemisorption interaction between H and Mg surface, but also benefits H atom diffusion in Mg bulk with relatively more diffusion paths compared with that of clean surface. Besides, hydrogen atom is found to occupy mostly the tetrahedral interstice when it diffuses into the Mg bulk. Further analysis of the density of states (DOS) shows that the system for hydrogen atom to be adsorbed at fcc site has a lower DOS value (N (E _F)) at Fermi level and more bonding electrons at the energy range blow the Fermi level of H/Mg (0001) system as compared with that at hcp site. On the other hand, the enhanced chemisorption interaction between hydrogen and defective surface should be attributed to the fact that the electronic structures of Mg (0001) surface are modified by an Mg vacancy, and the bonding electrons of the topmost layer Mg atoms are transferred from low energy range to Fermi level, which is in favor of improving the surface activity of Mg (0001) surface. Supported by the PhD Programs Foundation of Ministry of Education of China (Grant No. 200805321032), the Science and Technology Program Project of Hunan Province (Grant No. 2008GK3083) and the Program for Changjiang Scholars and the Innovative Research Team in university (Grant No. 531105050037)     

锂原子在Li(100)平坦表面和台阶面吸附扩散的行为

采用足够大的Cluster模拟了理想的Li(100)平坦表面和台阶面。用对势方法计算出了Cluster和Li原子的相互作用势,得到了吸附扩散势能面。给出了最佳吸附位在洞位;最低能量扩散通道为洞位→桥位→洞位。Li原子在台阶面的吸附扩散势表明,下台面形成捕获势、上台面形成反射势。     

Study on H atoms diffusion and adsorption properties of MgH<Subscript>2</Subscript>-V systems

Based on experimental results that VH_0.81/MgH₂ interface was found during the process of mechanically milling MgH₂+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH₂-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH₂ interface is formed due to V alloying MgH₂ phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH₂ phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH₂-V systems is reduced compared with that of MgH₂ phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH₂ across VH/MgH₂ interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH₂ phase region. Supported by the Ministry of Science and Technology of China (Grant No. 2006CB605104) and the National Natural Science Foundation of China (Grant No. 50771044)     

First-principles study on adsorption of Au atom on hydroxylated SiO<Subscript>2</Subscript> surface

Adsorption of single gold (Au) atom at three kinds of sites (hollow, bridge and top) on the hydroxylated β-cristobalite SiO2 (1 1 1) surface was studied using the first-principles calculations with general gradient approximation (GGA). The results of adsorption energies and density of electronic states (DOS) suggest that the hollow and bridge sites have the basically equal capability of binding Au, while the ability of the Top site is weaker. Two new energy levels emerge after the adsorption at all sites; i...     

石墨烯/h-BN面内异质结构热输运的分子动力学研究

采用非平衡分子动力学方法探究石墨烯/h-BN面内异质结构界面热导的影响因素,讨论了单空位缺陷和Stone-Wales (SW)缺陷在近界面不同位置时的声子热输运活动。模拟结果证明,当h-BN一侧单空位缺陷远离界面,界面热导随之降低; SW缺陷则由共价键类型和位置决定其对界面热导的影响,由此揭示缺陷的类型和位置对界面热导带来的调节作用。此外,讨论了界面处存在单空位缺陷时,温度变化影响界面热导背后的潜在机理。本研究对微观尺度下的二维异质结构材料的热导性能提供理论参考和实验指导。     

H2在Pt（111）表面吸附及电催化的密度泛函理论

Pt是燃料电池的重要电催化剂,为研究H2在Pt表面的吸附和氧化行为,采用密度泛函理论,通过构造表面层模型方法,对H2分子在金属态和电极Pt(111)表面Top、Bridge和Hollow三种吸附位进行研究。 H2在Pt(111)表面Hollow位吸附能最大,Top位吸附能最小;电极表面吸附能远大于金属态表面吸附能。吸附过程中H—H键被拉长,吸附后H—H键振动频率比自由分子振动频率减少,产生明显红移。电吸附过程中电子由H2分子向电极Pt(111)表面进行了不同程度的转移。计算结果与实验结果十分相近,从理论上解释了H2在电极Pt表面的电吸附和电催化机理。