类金刚石薄膜sp~2-sp~3轨道杂化的第一性原理研究

以强σ键连接的sp2和sp3杂化碳饱和簇模型,即金刚石和石墨两相和团簇模型为研究对象,通过分子结构、电荷分布、能带结构、电子态密度和分子轨道的第一性原理计算和分析,研究了类金刚石薄膜中sp2-sp3轨道杂化的空间结构稳定性的成键特性等.结果表明,成键过程中由于微扰作用破坏了原子内部"吸引"与"排斥"的平衡关系,使电子云重新分布,而键能大小和电子云的重叠密切相关,因而两相共存对电荷分布和结构均有影响.能带结构分析发现sp2杂化C原子将π键引入,产生π和π*能带使带隙变窄,说明类金刚石薄膜的半导体本质.电子态密度计算结果中费米能级附近出现杂质峰,说明存在中间杂化和/或π态和σ态的转化.     

类金刚石碳薄膜对碳膜导电性能的影响

以聚酰亚胺薄膜为原料,经炭化形成碳膜;进而在碳膜表面制备了类金刚石碳(DLC)薄膜,研究了制备条件对碳膜导电性能的影响.采用扫描电镜分析了薄膜的表面形貌和微观结构;采用X射线衍射仪分析了薄膜的晶体结构.结果表明,DLC薄膜的电阻率随着沉积时间的延长先减小后增加;当沉积时间达到3 h时,相应DLC薄膜的电阻率达到最小值5.66×10-5Ω.m.     

液相电化学沉积类金刚石薄膜的研究进展

采用电化学沉积法开展液相中类金刚石薄膜的制备工艺和理论的研究,对于完善类金刚石薄膜的合成技术,开拓类金刚石薄膜的应用领域,具有很重要的理论意义和实用价值。本文概述了液相电沉积技术的基本原理和方法,重点从四个方面介绍了电化学方法制备类金刚石薄膜的研究进展,总结了该方法所制备样品的性能,并对可能的反应机制作了综合性的阐述,最后对液相电沉积类金刚石薄膜的发展前景进行了展望。     

SIMS研究人造金刚石与金属膜的界面结合强度

文中利用SIMS研究了人造金刚石与金属膜的界面结合强度。结果表明;金刚石与钛膜的结合强度高于与镍膜的结合强度,热处理的结合强度高于未处理的强度。     

类金刚石薄膜表面的氨基修饰

采用射频磁控溅射法在双面抛光Si(100)基片上制备了类金刚石薄膜,通过磁过滤等离子体化学气相沉积法,以N2、H2混合气体为反应溅射气体,对类金刚石薄膜样品表面进行氨基改性.傅立叶变换红外透射光谱(FT-IR)的结果表明,改性后的类金刚石薄膜上有C-NH2键存在;光电子能谱(XPS)的结果表明,改性后的薄膜表面含氮量约为8.92%,N1s的结合能出现在氨基对应的结合能范围内,表明类金刚石薄膜经过适当改性后可以在薄膜表面产生氨基.     

制备类金刚石薄膜过程中的等离子体发射光谱

测定了不同反应条件下, 不同空间位置的等离子体发射光谱, 并与相应条件下生成的类金刚石薄膜的红外吸收谱进行对照, 分析了它们之间的关系。     

直流负偏压对类金刚石薄膜结构的影响

在不同的直流负偏压下利用直流射频等离子体辅助化学气相沉积技术在单晶硅表面沉积得到了类金刚石薄膜,用拉曼光谱、红外光谱和原子力显微镜对薄膜的结构和形貌进行了表征.结果表明:无偏压时,沉积得到的薄膜呈现类聚合物结构且表面比较粗糙,而叠加了偏压后,薄膜表现出类金刚石薄膜的结构特征,随着偏压的增大,膜中的氢含量和sp3碳含量均逐渐减小,且薄膜的表面粗糙度逐渐减小.     

乙腈中电化学法制备类金刚石薄膜

利用液相电沉积的方法在1600V,60℃条件下,从乙腈中沉积出类金刚石薄膜,发现了电流密度随反应时间呈波动变化的规律,并利用原子力显微镜和透射电子显微镜对薄膜不同生长阶段的形貌进行了考察.     

新金刚石电子结构的第一性原理研究

金刚石、 石墨和卡宾碳是三种常见的碳同素异构体, 其外层轨道价电子分别是以sp³-, sp²-和sp¹-形式杂化而成的^［1］. 1991年, Hirai等^［2］在研究金刚石的形成机理时, 发现了一种新的碳同素异构体, 并将其命名为新金刚石(new diamond) ^{［3, 4］}. 在许多实验过程中虽然也曾获得过新金刚石^［5~11］, 但是这些实验获得的新金刚石的样品产量都较少, 且新金刚石的颗粒尺寸都很小(小于100 nm), 因此只能采用电子衍射(ED)的方法研究其结构. Jarkov等^［9］在分析多晶体ED图谱的基础上, 认为新金刚石是面心立方结构(FCC), 其晶格常数为0.357 nm. 2001年, Konyashin等^［1］通过ED图谱、电子能量损失谱和半经验的能量计算认定新金刚石为FCC的纯碳, 其晶格常数为0.356 3 nm. 我们曾用强磁场碳黑催化法制备出大量的新金刚石^{［3,4,12~14］}, 并对新金刚石的热稳定性进行了研究^［12］, 而对其结构和性能的研究尚未见报道.     

Nano‐adhesion and friction of multi‐asperity contact: a molecular dynamics simulation study

In our study, the contact and sliding processes between a flat plate and a substrate with multiple asperities are studied by molecular dynamics (MD) simulations, and how the number of asperities and asperity height influence the adhesion force and friction force are investigated thoroughly. The normal force versus the separation distance curve during contact processes is analyzed completely and from which the van der Waals (vdW) force (F_vdW) and the adhesion force (F_adh) are obtained and compared with the Katainen model. The adhesion force and the friction force increase linearly as the increase of the number of asperities (i.e. real contact area) with same asperity height. With the identical number of asperities, the adhesion force and the friction force decrease with the increase of the asperity height at first. However the reductions of the adhesion force and the friction force become less obvious, when the asperity height is larger than a critical value (20 Å for our simulation parameters). Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular dynamics method in studies of molecular film growth processes

This review is an attempt to analyze some of the experimental problems arising in the course of growth of orientated molecular films using metal monophthalocyanine (MPc) films as an example and to demonstrate the possibilities of molecular dynamics simulation of these processes for solving experimental problems. Examples of theoretical simulation of adsorption processes are given; formation of a molecular monolayer is considered for copper phthalocyanine films as an example.     

麋鹿朊蛋白结构稳定性的分子动力学研究

朊蛋白病是一种致命且具有高度传染性的神经退行性疾病.糜鹿是目前已经报道的哺乳类动物中较易发生朊蛋白病的物种之一.作者使用分子动力学和操控式分子动力学模拟相结合的方法对糜鹿正常朊蛋白的结构稳定性进行了研究.发现了麋鹿朊蛋白结构中的不稳定结构域分布以及热动力学性质,揭示了糜鹿朊蛋白稳定性的分子结构基础以及力学特征.     

Molecular dynamics simulations of the effects of carbon dioxide on the interfacial bonding of polystyrene thin films

Fabrication of nanoscale polymer‐based devices, especially in biomedical applications, is a challenging process due to requirements of precise dimensions. Methods that involve elevated temperature or chemical adhesives are not practicable due to the fragility of the device components and associated deformation. To effectively fabricate devices for lab‐on‐a‐chip or drug delivery applications, a process is required that permits bonding at low temperatures. The use of carbon dioxide (CO₂) to assist the bonding process shows promise in reaching this goal. It is now well established that CO₂ can be used to depress the glass transition temperature (T_g) of a polymer, allowing bonding to occur at lower temperatures. Furthermore, it has been shown that CO₂ can preferentially soften a polymer surface, which should allow for effective bonding at temperatures even below the bulk T_g. However, the impact of this effect on bonding has not been quantified, and the optimal bonding temperature and CO₂ pressure conditions are unknown. In this study, a molecular dynamics model is used to examine the atomic scale behavior of polystyrene in an effort to develop understanding of the physical mechanisms of bonding and to quantify how the process is impacted by CO₂. The final result is the identification of a range of CO₂ pressure conditions which produce the strongest bonding between PS thin films at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

兔子朊蛋白结构稳定性的分子动力学研究(英文)

朊蛋白病是一种能够对人类和动物带来致命影响,并具有高度传染性的神经退行性疾病.兔子是目前已经报道的哺乳类动物中对朊蛋白病免疫的少数几个物种之一.我们将分子动力学和操控式分子动力学模拟相结合,研究了兔子正常朊蛋白的结构稳定性;同时讨论了蛋白结构的收敛性及刚性分布,并揭示了兔子朊蛋白中关键二级结构的动力学以及受力各向异性特征,证实了兔子朊蛋白结构的稳定性特征.     

Steered molecular dynamics simulations for uncovering the molecular mechanisms of drug dissociation and for drug screening: A test on the focal adhesion kinase

Drug‐binding kinetics could play important roles in determining the efficacy of drugs and has caught the attention of more drug designers. Using the dissociation of 1H‐pyrrolo[2,3‐b]‐pyridines from the focal adhesion kinase as an example, this work finds that steered molecular dynamics simulations could help screen compounds with long‐residence times. It also reveals a two‐step mechanism of ligand dissociation resembling the release of ADP from protein kinase A reported earlier. A phenyl group attaching to the pyrrole prolongs residence time by creating a large activation barrier for transition from the bound to the intermediate state when it becomes exposed to the solvent. Principal component analysis shows that ligand dissociation does not couple with large‐scale collective motions of the protein involving many of its amino acids. Rather, a small subset of amino acids dominates. Some of these amino acids do not contact the ligands directly along the dissociation pathways and could exert long‐range allosteric effects. © 2018 Wiley Periodicals, Inc.     

金属晶体间微观静摩擦特性的分子动力学模拟研究

以光滑干摩擦接触平面为对象,利用金属晶体间的强体积效应特征,建立了简化计算静摩擦力的界面势能模型.根据第一性原理的方法模拟得出界面分子势能的变化,通过界面分子势能计算出静摩擦力大小,并将数据结果通过通用黏附能量函数计算出的静摩擦力大小进行验证,也将计算结果与超高真空原子力显微镜试验结果进行对比.最后拟合出最大静摩擦力与法向载荷的线性函数关系,得出摩擦力的数值为真实接触面积的函数,并与法向载荷成正比的结论.从微观上对同种金属材料间库伦摩擦定律进行验证与研究.