不同晶向Cu纳米线结构和电子特性的第一性原理计算

基于密度泛函理论框架下的第一性原理计算方法,系统研究了[100]、[110]和[111]3个低指数晶向不同尺寸Cu纳米线的弛豫结构和电子特性。由于配位数的减少,纳米线表面原子向内收缩且角部区域内的原子弛豫量较大,即存在着"倒棱"现象。纳米线的结合能随着其线径的增加而增加,[110]晶向六边形结构的Cu纳米线最稳定,这与在实验中最容易形成该晶向纳米线的结果一致。纳米线表面原子与其最近邻原子间的相互作用明显增强,因此相对于体相Cu晶体,纳米线的力学性能得以提高。所有Cu纳米线都具有金属性,且其量子电导随着线径的增加而增大。     

Cu掺杂ZnS纳米线结构和磁性质

本文采用第一性原理密度泛函理论系统地研究了Cu原子掺杂ZnS纳米线的结构、电子性质和磁性质.所有掺杂纳米线的形成能比纯纳米线的形成能低,说明掺杂过程是放热的.并且Cu原子趋于替代纳米线的表面的Zn原子.电子结构显示Cu掺杂纳米线是半金属铁磁半导体材料,在自旋电子学方面有重要应用.     

高温下Fe_73Cu_1.5Nd_3Si_13.5B_9非晶合金结构演化的原位X射线研究

利用原位X射线衍射测量结构参数方法,研究了Fe_73Cu_1.5Nd_3-Si1_3.5B_9非晶合金热力学结构弛豫.通过Fourier变换得到不同温度的径向分布函数、近邻原子间距等原子构型的结构信息.研究结果表明,发生热力学结构弛豫时,大块金属玻璃的非晶结构保持稳定,但温度改变该非晶短程有序的次近邻局域原子构型.     

高温下Fe73CU1．5Nd3Si13．5B9非晶合金结构演化的原位X射线研究

利用原位X射线衍射测量结构参数方法,研究了Fe73Cu1.5Nd3-Si13.5B9非晶合金热力学结构弛豫．通过Fourier变换得到不同温度的径向分布函数、近邻原子间距等原子构型的结构信息．研究结果表明,发生热力学结构弛豫时,大块金属玻璃的非晶结构保持稳定,但温度改变该非晶短程有序的次近邻局域原子构型．     

Al和氧空位对ZnO:Co稀磁半导体磁性质的影响

利用基于密度泛函理论的第一性原理计算方法,研究了Al共掺杂和氧空位缺陷对Co掺杂ZnO磁性质的影响,发现Al原子共掺杂引入的自由电子载流子会稳定体系的反铁磁性从而减弱Co原子间的铁磁性交换,而氧空位缺陷束缚的电子载流子对提高体系的铁磁性具有积极的作用.氧空位引入的电子载流子部分转移到Co原子和近邻Zn原子,形成以电子载流子为媒介的Co原子间的耦合作用,稳定体系的铁磁态,增强Co原子间的交换耦合作用.     

Fe掺杂ZnO纳米线电子性质和磁性质

本文采用第一性原理密度泛函理论系统地研究了Fe原子单掺杂和双掺杂ZnO纳米线的电子性质和磁性质.所有掺杂纳米线的形成能都比纯纳米线的形成能低,说明掺杂过程是放热的.计算结果显示Fe原子趋于占据纳米线表面位置.纳米线的总磁矩主要来源于Fe原子3d轨道的贡献.由于杂化,相邻的O原子也产生了少量自旋.在超原胞内,Fe、O原子磁矩平行排列,表明它们之间是铁磁耦合.表面掺杂纳米线显示出半导体特性,而中间掺杂纳米线显示出半金属性,在自旋电子学领域有广泛应用.     

闪锌矿结构链中的非线性表面局域模

利用数值计算研究了近邻原子质量和作用力常数均不同的一维链中的非线性表面局域模,该模型模拟闪锌矿结构晶体中〈111〉方向一列表面原子的非线性振动.在考虑近邻原子间相互作用势函数中的四次方非线性项后,在相应线性系统频带的禁带中和光学支上面发现了非线性表面局域模(S1模和S2模).在考虑近邻原子间相互作用势函数中的三次方和四次方非线性项时,非线性表面局域模中出现静态"直流"分量,表面局域模振动频率降低.结果还表明在相应线性系统频带的光学支上面和禁带中是否存在非线性表面局域模与三次方、四次方非线性项和最大的可能达到的位移有关.     

过渡金属掺杂ZnO纳米线结构、电子性质和磁性质

本文采用密度泛函理论系统地研究了过渡金属原子Co和Ni单掺杂和双掺杂ZnO纳米线的结构、电子性质和磁性质.所有掺杂纳米线的束缚能都为负值,表明掺杂过程是放热的. Co原子趋于占据纳米线中间位置,而Ni原子趋于占据纳米线表面位置.所有掺杂纳米线能隙都小于纯纳米线能隙,并显示出直接带隙半导体特性.纳米线的总磁矩主要来源于磁性原子的贡献. Co掺杂纳米线出现了铁磁和反铁磁两种耦合状态;而Ni掺杂纳米线出现了铁磁、反铁磁和顺磁三种耦合状态.     

C掺杂ZnS纳米线电子性质和磁性质

运用第一性原理方法研究了C掺杂ZnS纳米线的电子性质和磁性质.研究发现C原子趋于替代纳米线表面的S原子.所有掺杂纳米线显示了半导体特性.纳米线的总磁矩主要来源于C原子2p轨道的贡献.由于杂化,相邻的Zn原子和S原子也产生了少量自旋.在超原胞内,C、Zn和S原子磁矩平行排列,表明它们之间是铁磁耦合.铁磁态和反铁磁态的能量差达到了121meV,表明C掺杂ZnS纳米线可能存在室温铁磁性,这在自旋电子学领域有很大应用前景.     

金属Al、Cu钝化机理电子理论研究

通过计算机编程建立水吸附Al和Cu的模型,利用实空间的Recussion方法分别计算了Al和Cu被H2O吸附前后系统的状态密度和能量变化,及表面金属原子与其近邻原子间的键级积分,并将两个计算结果进行比较.从结果中分析,金属原子的电子转移到H2O分子的O原子上.水吸附金属表面后,状态密度有所下降,次表面原子几乎不受影响,系统总能降低,系统变稳定.H2O使金属表面化学活性降低,并从键级积分计算结果中讨论了Al和Cu钝化膜的形成机理:水通过氧与金属表面原子成键后,表面金属原子与次表面原子作用增强,水中氧和氢原子相互作用改变的不同导致形成不同的钝化膜.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the