锂的物态方程及相结构稳定性

 用能带论LMTO方法，在对bcc、fcc锂的能带结构进行自洽计算的基础上，对两种结构的物态方程做了计算。压缩比1～12、压力至10³ GPa的计算结果分别与实验（σ<3）及TF统计模型进行了比较。通过对总能的计算，研究了晶体结构的稳定性。说明在我们所研究的压力范围内，fcc结构比bcc结构更稳定。     

硅纳米颗粒在碳纳米管表面生长的分子动力学模拟

采用分子动力学模拟方法研究了硅纳米颗粒在碳纳米管上的生长，并分析了这种复合材料的基本结构.研究表明，由于硅原子和碳纳米管之间的相互作用以及碳纳米管的巨大的表面曲率，硅原子在碳纳米管表面不是形成覆盖碳纳米管的二维薄膜，而是生成具有三维结构的硅纳米颗粒.小纳米颗粒的结构和无基底条件下生成的颗粒结构基本一致.对于大纳米颗粒，不同于无基底条件下形成的球状纳米晶体硅结构，硅纳米颗粒沿管轴方向伸长，其结构为类似于硅晶体的无定形网络结构. 关键词： 纳米颗粒 碳纳米管 硅 分子动力学模拟     

Fe在Ru(1010)表面上沉积的LEED，ARUPS研究

Fe在Ru(1010)表面上的沉积,经过LEED和ARUPS的测量研究.结果表明,经过退火Fe在Ru(1010)表面根据覆盖度大小分别形成(1×1)和P(2×1)结构.当覆盖度大于10个单层时,表面结构不再保持与衬底相关的晶格常数与对称性,形成fcc铁的(111)外延结构.铁覆盖度较小时,费米能级附近的价电子能级与清洁时相似,外延fcc铁表面则形成了与表面有关的价电子能级. 关键词：     

C60分子在GaAs(001)表面的外延生长的扫描隧道显微镜研究

利用扫描隧道显微镜（STM）系统地研究了C₆₀薄膜在GaAs（001）表面的异质外延生长．在GaAs（001）2×4-β相表面，观察到C₆₀薄膜以非密排面进行生长，并在生长中有结构相变产生．实验数据表明，薄膜下层面心立方（fcc）的晶格常数比C₆₀晶体的晶格常数要大13%；而薄膜的表层结构则展示了非理想的六角密堆（hcp）结构，其表面为hcp（1100）面，生长过程是非理想的层状生长模式．在GaAs（001）-c（4×4）衬底上，C₆₀薄膜的表面仍然是fcc（111）面，其结构参数与C₆₀晶体一致，但C₆₀薄膜采用了三维模式进行生长 关键词：     

轴向拉伸对Ni纳米线结构和稳定性的影响

采用推广模拟退火算法和Sutton Chen势, 选取fcc[111]结构的Ni纳米线为初始构型, 研究了轴向拉伸对Ni纳米线的结构和稳定性的影响。 研究结果表明: 拉伸程度的大小对Ni纳米线的结构和稳定性有很大的影响; 随着拉伸强度的变化, 纳米线结构分别为fcc[111]结构、 (6, 0)型管＋中心柱状结构（又为螺旋结构）、 (6, 3) 型管＋中心柱状结构、 fcc[110]结构、 过渡结构（为规则结构）和缺陷结构; 从结合能分布来看, 结合能先减小, 再增大, 结合能最小时对应最稳定结构 (6, 0) 型管＋中心柱状结构（又为螺旋结构）。 Atomic structures and stabilities of Ni nanowires are studied by using the generalized simulated annealing method with Sutton Chen potential. The initial structure is face centered cubic [111] structure. The result shows that the length of the supercell strongly affects the structures and stabilities of Ni nanowires. fcc [111] structure, (6, 0), (6, 3) nanowires, fcc[110], transition structure and defect structure are found for different wire lengths. And from the analyses of the binding energy, it is found that (6, 0) nanowires (helical structure) is the most stable form.     

外压下ZrN结构相变的第一性原理研究

利用基于密度泛函理论的赝势平面波方法,研究了面心立方(fcc)和体心立方(bcc)结构ZrN的平衡态性质以及不同压力下的弹性性质,计算了fcc和bcc结构ZrN的焓-压关系,讨论了其相对稳定性。通过对总能、焓-压关系、弹性性质以及声子色散关系的分析,推测fcc结构到bcc结构的相变发生在205~235GPa之间。     

O在Au(111)表面吸附的密度泛函理论研究

应用密度泛函理论，本文系统地研究了O在Au(111)表面上的吸附能、吸附结构、功函数、电子密度和投影态密度，给出了覆盖度从0.11ML到1.0ML的范围内，O的吸附特性随覆盖度变化的规律.研究发现O的稳定吸附位为3重面心立方(fcc)洞位，O在fcc洞位的吸附能对覆盖度比较敏感，其值随着覆盖度的增加而减小；O诱导Au(111)表面功函数的变化量与覆盖度成近线性关系，原因是Au表面电子向O偏移，形成表面偶极子；O—Au的相互作用形成成键态和反键态，且反键态都被占据，造成O—Au键很弱，O吸附能较小. 关键词： 表面吸附 Au(111)表面 密度泛函理论 电子特性     

金属fcc(100)表面吸附原子的自扩散现象

通过静态计算和分子动力学方法 ,系统地研究了吸附原子在金属fcc( 10 0 )表面的自扩散现象 ,所采用的模型势是一系列由原子嵌入方法 (EAM )得到的。结果表明金属fcc( 10 0 )表面可分为三种不同的类型 ,即硬、中性和软。而且发现在大多数表面 ,如硬的和许多中性表面的简单交换机制都是通过“应力产生和释放”的模型 ,而不是以前所认为“合作运动”模型 ,只有在软表面“合作运动”模型才变得重要。另外 ,在软表面上还观察到了另一种形式的复杂交换机制 ,它不同于“应力产生和释放”模型基础上的复杂交换机制。     

Ni纳米线的结构和性质研究

采用推广模拟退火算法(Generalized Simulated Annealing,GSA)和Sutton-Chen势,研究了初始构型为面心立方(fcc)结构的Ni纳米线,在沿径向压缩时的结构和性质.结果表明:径向压缩程度对Ni纳米线的结构有很大的影响.当Ni纳米线直径大于0.398nm时(初始直径为0.498nm),其结构由fcc结构变为类似fcc结构,但结合能变化很小,表明其结构之间几乎可以实现零能量转换,且稳定性基本不变;当Ni纳米线直径小于0.398nm时,其结构从无定形结构变为缺陷结构,结合能迅速上升,表明其结构稳定性降低;键角的分布也证明了以上结果的正确性.     

通过电沉积及氟硅烷改性而成的三维铜镍复合超疏水表面（英文）

将Cu-Ni微纳米颗粒电沉积在铝基底上,通过1H、1H、2H、2H-全氟癸基三甲氧基硅烷(FAS-17)对其进行修饰,制备了超双疏(SAP)表面.采用扫描电子显微镜、X射线衍射、能量色散X射线光谱和傅里叶变换红外光谱对其形貌和化学成分进行了研究.结果表明,SAP表面具有三维微纳结构,最大水接触角160.0°,油接触角151.6°.进一步测试了SAP表面的机械强度和化学稳定性,结果显示该SAP表面具有优良的耐磨性、耐酸耐碱性能、自洁性和防污性能.     

Decay characteristics of surface mounds with contrasting interlayer mass transport channels

The decay characteristics of three-dimensional (3D) islands formed on surfaces are investigated theoretically considering two types of interlayer mass transport mechanisms. If an adatom on a given layer can easily descend from any site along the periphery of the layer, an optimal island slope and a constant terrace width will be selected during the decay. In contrast, if the adatom can descend primarily through selective (such as kinked) sites, the decay will be accompanied by a gradual increase in the island slope. These generic conclusions provide the basis for a microscopic understanding of the decay of nanostructures in fcc(111) and fcc(100) metal homoepitaxy and are applicable to other systems as well.     

Anomalous scaling in heteroepitaxial island dynamics on Ag(100)

Diffusion and decay of alloyed Cu/Ag islands are investigated in the size range from 1 to 40 nm2 on Ag(100) at room temperature with fast-scanning tunneling microscopy and density functional theory. While islands at sizes above 7 nm2 show the diffusion and decay behavior expected for dynamics based on single atom hopping, islands smaller than 4 nm2 diffuse faster and decay slower than predicted by standard theory. This anomalous behavior at unexpected large island sizes is related to a size dependent dealloying of the Cu/Ag islands.     

Reduction of Cu2O islands grown on a Cu(100) surface through vacuum annealing

The reduction of Cu2O islands grown on Cu(100) surfaces through vacuum annealing was visualized by an in situ ultrahigh vacuum transmission electron microscope. The shrinkage of the island followed a linear decay behavior. The complete reduction of the oxide islands leads to the formation of nanoindentations on the Cu surfaces. A simple phenomenological kinetic model based on the dissociation along the island perimeter suitably describes the reduction behavior of the surface oxide islands.     

原子表面扩散的对称破缺对二维岛形成的控制

文章阐述了当CO吸附改变时Pt/Pt(111)同质外延单层岛的的微观选择机制，即岛的取向由沉积原子的边－角扩散运动的不对称性惟一决定，对没有CO介入的理想真空生长情况，衬底温度不能改变三角形岛的取向。CO的吸附反转了边－角扩散牟不对称性，从而使岛的取向发生变化。     

Island shape selection in Pt(111) submonolayer homoepitaxy with or without CO as an adsorbate

The microscopic selection mechanisms of single-layer island shapes in Pt(111) homoepitaxy with or without minute amounts of CO adsorbate have been investigated theoretically. For clean growth, only triangular islands of a fixed orientation are obtained within a wide range of growth temperatures, with the orientation uniquely determined by a disparity in the rates of atom supply to an island corner site from the two island edges defining the corner. This novel picture is further corroborated by growth predictions in the presence of CO, whose preferential decoration of one type of the island edges reverses the intrinsic rate disparity for atom supply, thereby inverting the island orientation.     

Cu-Au体系非对称异质外延行为的分子动力学研究

利用分子动力学模拟方法研究了Cu/Au(001)和Au/Cu(001)异质外延岛的演化行为. 研究结果显示：Cu-Au体系的相互外延行为呈现出明显的非对称性. Cu在Au(001)基体表面可以形成完整的外延结构，而Au在Cu(001)基体表面外延将导致失配位错的出现. 导致非对称外延生长行为的根本原因是外延岛的应变状态的差异和外延岛自身性质的不同. 随着外延岛的长大，Cu外延岛与Au(001)基体的微观失配度由最初的接近宏观失配度的9%左右迅速单调下降，并最终趋于晶格匹配；而Au在Cu(001)基体表面外延的微观失配度则呈现出振荡增加趋势. Cu/Au(001)体系的基体形变主要发生在外延岛的边缘，而Au/Cu(001)体系的基体形变主要发生在外延岛内部所对应的区域.     

3D KMC simulations of crater growth during the reduction of oxide nanoislands on metal surfaces

The homoepitaxial growth of Cu nanocraters induced by thermal reduction of Cu₂O nanoislands on Cu(100) surfaces is simulated using a three-dimensional (3D) kinetic Monte Carlo (KMC) model by incorporating surface diffusion, attachment and detachment Cu adatoms dislodged from reducing Cu₂O islands. The craters are observed to grow continuously in rim height and rim slopes while remaining relatively constant in rim width in the course of the oxide decomposition. Such a growth behavior is attributed to the climbing uphill of Cu adatoms released from the perimeter of the reducing Cu₂O island at the crater bottom. The observed decay of the rim height and slopes after completion of the reduction of oxide islands suggests that these surface craters are thermodynamically unstable at high temperatures.     

The molecular dynamic study of anharmonic effects at Cu(111) and Ag(111) surfaces in the presence of Cu- and Ag-trimer island

The molecular dynamics (MD) technique based on semi-empirical potentials, is used to carry out the diffusion of Cu- and Ag-trimer on Cu- and Ag(111) surface at 300, 500 and 700 K temperatures. The constant energy MD simulation elaborates the anharmonic effects at the surface such as fissures, dislocations and vacancy creation, in the presence of island. The fissures and dislocations formed are in the range of 1.5–4 Å and 1–7 Å, respectively, from the island's position. The Cu and Ag islands both diffuse easily on Cu(111) surface, manipulate that the trend of diffusion is faster on Cu surface as compared to Ag surface. The process of breaking and opening of the island has also been observed. Moreover, a surface atom popped-up at 700 K by creating a vacancy near the Cu island on Ag surface. The rate of diffusion increases with the increase in temperature, both for homo- and hetero-cases.     

Formation of nanoislands in the course of copper deposition on a Cu(111)-(9 × 9)-Ag surface

The process of copper deposition on a structured Cu(111)-(9 × 9)-Ag surface, which represents a (9 × 9) loop dislocation network, is studied by scanning tunneling microscopy. It is found that, when the substrate temperature is 100 K and the copper coverage is 0.1–0.4 of a monolayer, islands of a size no greater than 50 Å are formed at the Ag/Cu(111) interface. The islands remain stable as the sample is heated to room temperature. The shape and boundaries of the nanoislands follow the initial surface superstructure and are determined by the nonuniformity of the interaction of the upper silver layer with the copper substrate. The mechanism of island formation and the origin of their stability are explained in terms of the atom exchange between the adsorbate and substrate.     

Quantum size effects in adatom island decay

The decay of hexagonal Ag adatom islands on top of larger Ag adatom islands on a Ag(111) surface is followed by a fast-scanning tunneling microscope. Islands do not always show the expected increase in decay rate with decreasing island size. Rather, distinct quantum size effects are observed where the decay rate decreases significantly for islands with diameters of 6, 9.3, 12.6, and 15.6 nm. We show that electron confinement of the surface state electrons is responsible for this enhancement of the detachment barrier for adatoms from the island edge.