氢原子在金属锂表面台阶附近吸附和表面扩散行为的ab initio研究

取Li7H和Li9H两个原子簇模拟氢原子与含台阶的金属锂表面的相互作用, 以小基组用ab initip方法计算了体系的吸附和表面扩散势能面(或势能曲线)。结果表明: (1)对Li7H体系, 台阶面附近沿垂直边棱方向存在三种不同的桥位吸附位, 最稳定的吸附位在上台面接近台阶边棱处, 台阶面显著地改变了表面扩散活化能, 台阶边棱处有一个较高的势垒。于是, 迁移原子将会在台阶边棱处受到反射, 并可被捕获于台阶面上及其附近。由势能面确定了最低能量表面扩散途径。(2)对Li9H体系, 在Li7H原子簇基础上增加次表面层两个锂原子后, 表面扩散活化能略有减小, 氢原子在上台面的桥位吸附更趋稳定, 各吸附位相对稳定性及势垒内何位置几无改变, 这些结果显示了台阶面对氢原子的化学吸附和表面扩散发生扰动, 台阶边棱对表面扩散起着重要作用。     

不同覆盖度下Li原子在Si(001)表面上的吸附构型和电子结构

采用基于赝势平面波基组的密度泛函理论, 对不同Li原子覆盖度下Li/Si(001)体系的吸附构型、电子结构以及吸附Li原子对表面性质的影响进行了系统研究. 计算结果表明, 在所考察的覆盖度范围内, Li原子倾向于吸附在相邻两个Si-Si二聚体之间各种对称性较高的空穴位, 其中覆盖度为0.75 ML(monolayer)时具有最小的平均吸附能. 由能带结构分析结果可知, 随着覆盖度的增大, Si(001)表面存在由半导体→导体→半导体的变化过程. 在覆盖度为1.00 ML时, 由于表层二聚体均受到显著破坏, 使得体系带隙明显增大. 吸附后, 有较多电子从Li原子转移到底物, 导致Si(001)表面功函显著下降, 并随着覆盖度的增加表面功函呈现振荡变化. 此外, 从热力学稳定性角度上看, 覆盖度为0.75 ML的Li/Si(001)表面较难形成.     

氢原子在Ru(0001)和Ru(1010)面上吸附扩散势能面的结构

本文构造了H-Ru相互作用的五参数Morse势,用经典的对势方法研究了氢原子在Ru(0001)和Ru(1010)面上的吸附和扩散,得到了氢原子在两个表面上的吸附位、吸附几何、结合能及本征振动等数据与实验结果符合得很好;同时研究了两个体系的吸附扩散势能面结构。     

氮原子在Ni平坦和缺陷表面上的吸附和振动

 构造了氮－镍相互作用的5－参数Morse势，研究了氮原子在Ni（\r\n100），Ni（110）和Ni（111）平坦表面的吸附和振动，获得了氮原子\r\n在三个低指数表面的吸附位、吸附构型、结合能和本征振动等数据，计\r\n算结果与实验结果非常吻合．同时，与Ni（100）表面对比，系统研究\r\n了氮原子在Ni（510）台阶面的吸附和扩散．计算结果表明，氮原子在\r\n台阶下部形成最稳定的吸附态，台阶对下台面上扩散的氮原子形成捕获\r\n势，对上台面上扩散的氮原子形成反射势．     

氢原子在Ni(100), Ni(111)和Ni(110)面上吸附扩散势能面的结构

本文构造了氢-镍相互作用的5参数Morse势, 用经典的对势方法研究氢原子在Ni(100), Ni(111)和Ni(110)面上的吸附和扩散, 得到氢原子在三个表面上的吸附位、吸附几何、结合能及本征振动等数据, 和实验结果符合得很好。同时, 系统地研究了三个体系的吸附扩散势能面结构。     

氢原子在Ru(0001)和Ru(100)面上吸附扩散势能面的结构

本文构造了H—Ru相互作用的五参数Morse势,用经典的对势方法研究了氢原子在Ru(0001)和RU(1010)面上的吸附和扩散,得到了氢原子在两个表面上的吸附位、吸附几何、结合能及本征振动等数据与实验结果符合得很好;同时研究了两个体系的吸附扩散势能面结构.     

氢原子在镍台阶面上吸附、振动和表面扩散行为的理论研究

本文用对势方法研究了氢原子在Ni(510)台阶面上的吸附和振动, 计算结果与实验符合得很好。并考察了氢原子在Ni(997)台阶面上的吸附和扩散, 结果表明,台阶对下台面上扩散的氢原子开成捕获势阱, 对上台面扩散的氢原子形成反射势,这也很好地支持了实验结果。     

氢原子在金属锂表面台阶附近吸附和表面扩散行为的ab initio研究

取Li_7H和Li_9H两个原子簇模拟氢原子与含台阶的金属锂表面的相互作用,以小基组用abinitio方法计算了体系的吸附和表面扩散势能面(或势能曲线),结果表明:(1)对Li_7H体系,台阶面附近沿垂直于边棱方向存在三种不同的桥位吸附位,最稳定的吸附位在上台面接近台阶边棱处,台阶面显著地改变了表面扩散活化能,台阶边棱处有一个较高的势垒,于是,迁移原子将会在台阶边棱处受到反射,并可被捕获于台阶面上及其附近,由势能面确定了最低能量表面扩散途径,(2)对Li_9H体系,在Li_7H原子簇基础上增加次表面层两个锂原子后,表面扩散活化能略有减小,氢原子在上台面的桥位吸附更趋稳定,各吸附位相对稳定性及势垒几何位置几无改变,这些结果显示了台阶面对氢原子的化学吸附和表面扩散发生扰动,台阶边棱对表面扩散起着重要作用。     

氢原子在平坦金属锂(100)面上表面扩散行为的ab initio研究

本文用Li7(4,3)-H和Li9(5,4)-H小原子簇模拟氢原子在平坦金属锂(100)面吸附体系, 取小基组作了各吸附位吸附势能曲线及相应分子轨道能级图、吸附和表面扩散势能面的ab initio研究。结果表明, 氢原子优先吸附在配位数较高的吸附位上, 并倾向于由高配位数吸附位向低配位数吸附位迁移, 表面扩散各向异性, 扩散跳跃步长与锂单晶晶格原子间距数量级相同。从吸附和表面扩散势能确定了最低能量表面扩散途径, 分析了原子在平坦金属表面上迁移的微观过程。     

氢原子在钯低指数表面上的吸附和扩散

采用氢－钯相互作用的五参数Ｍｏｒｓｅ势，用对势方法研究了氢原子在Ｐｄ（１００）、Ｐｄ（１１１）和Ｐｄ（１１０）低指数平坦表面上的吸附和扩散，得到氢原子在三个表面上的吸附位、吸附几何、结合能和本征振动等数据，计算结果和实验结果符合得很好。在此基础上，系统地研究了三个系统的吸附扩散势能面结构。     

The Li ion transport behavior in the defect graphene composite Li3N SEI: a first-principle calculation

An artificial solid electrolyte interface (SEI) of a graphene composite lithium salt can inhibit the growth of dendrites by driving the lithium deposition behavior on the surface of the lithium metal anode. The first-principle method was used to calculate the graphene/lithium nitride SEI, including the structural form and stability of intrinsic (G-Li₃N), single-vacancy defect (SVG-Li₃N), and double-vacancy defect (DVG-Li₃N) graphene heterostructure. The adsorption and migration behavior of lithium ions on the heterostructure surface and the interface were also calculated. This study showed that the modification of double-vacancy defect graphene improved the stability of the heterostructure, and the adhesion work of the composite SEI is the highest. The modification of defective graphene increases the adsorption energy of lithium atoms on the surface and interface of the heterostructure: the strongest adsorption of Li atoms on the single-vacancy defect region of the heterostructure, the opposition migration pathway of Li atoms on the surface and interface of the DVG-Li₃N heterostructure, and the decrease diffusion energy of Li atoms on the surface and interface of the DVG-Li₃N heterostructure. A composite layered SEI of graphene and Li₃N was constructed to inhibit dendritic growth by adjusting the deposition behavior of lithium atoms.     

锂在非层状硫化物中的电化学嵌入反应I:锂在硫化铅中的嵌入过程

通过库伦滴定、三角波电位扫描和X射线衍射物相分析,研究了Li/PbS电池的阴极反应机理.发现在该电池放电的第一个阶段(放电深度小于1.5),阴极上发生的是锂嵌入硫化铅晶格的反应,并且锂嵌入后硫化铅的主晶格结构基本未变,锂进入了晶体的立方体间隙中心位置.测得锂嵌入硫化铅生成LiPbS的嵌入自由能为-300.48kJ.mol^-^1(25℃),锂在LiyPbS(0相似文献   

Enhanced Li Adsorption and Diffusion in Single‐Walled Silicon Nanotubes: An ab Initio Study

We report a first‐principles investigation of Li adsorption and diffusion in single‐walled Si nanotubes (SWSiNTs) of interest to Li‐ion battery anodes. We calculate Li insertion characteristics in SWSiNTs and compare them with the respective ones in carbon nanotubes (CNTs) and other silicon nanostructures. From our calculations, SWSiNTs show higher reactivity toward the adsorption of Li adatoms than CNTs and Si nanoclusters. Considering the importance of Li kinetics, we demonstrate that the interior of SWSiNTs may serve as a fast Li diffusion channel. The important advantage of SWSiNTs over their carbon analogues is a sevenfold reduction in the energy barrier for the penetration of the Li atoms into the nanotube interior through the sidewalls. This prepossesses easier Li diffusion inside the tube and subsequent utilization of the interior sites, which enhances Li storage capacity of the system. The improvements in both Li uptake and Li mobility over their analogues support the great potential of SWSiNTs as Li‐ion battery anodes.     

Li+ ionic conductivities and diffusion mechanisms in Li-based imides and lithium amide

In this study, both experimental ionic conductivity measurements and the first-principles simulations are employed to investigate the Li(+) ionic diffusion properties in lithium-based imides (Li(2)NH, Li(2)Mg(NH)(2) and Li(2)Ca(NH)(2)) and lithium amide (LiNH(2)). The experimental results show that Li(+) ions present superionic conductivity in Li(2)NH (2.54 × 10(-4) S cm(-1)) and moderate ionic conductivity in Li(2)Ca(NH)(2) (6.40 × 10(-6) S cm(-1)) at room temperature; while conduction of Li(+) ions is hardly detectable in Li(2)Mg(NH)(2) and LiNH(2) at room temperature. The simulation results indicate that Li(+) ion diffusion in Li(2)NH may be mediated by Frenkel pair defects or charged vacancies, and the diffusion pathway is more likely via a series of intermediate jumps between octahedral and tetrahedral sites along the [001] direction. The calculated activation energy and pre-exponential factor for Li(+) ion conduction in Li(2)NH are well comparable with the experimentally determined values, showing the consistency of experimental and theoretical investigations. The calculation of the defect formation energy in LiNH(2) reveals that Li defects are difficult to create to mediate the Li(+) ion diffusion, resulting in the poor Li(+) ion conduction in LiNH(2) at room temperature.