共查询到18条相似文献,搜索用时 164 毫秒
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硬球链流体在平板和硬球表面分布的密度泛函理论 总被引:1,自引:0,他引:1
采用Yethiraj和Woodward的密度泛函理论方法,结合胡英和刘洪来等发展的硬球链流体状态方程,得到了自由连接硬球链流体在平板狭缝中和球形固体颗粒表面附近的密度分布表达式,并计算了在两平行壁所组成的狭缝中和直径大小不同的球形固体颗粒周围硬球链分子的链节密度分布.理论计算结果与作者采用Dickman 和Hall 的方法进行Monte Carlo计算机模拟结果非常吻合.颗粒直径对链状分子的密度分布有一定的影响,随着固体颗粒直径的增加,靠近颗粒表面附近的链节密度降低. 相似文献
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为提高非定域密度泛函理论(NLDFT)预测活性炭孔径分布(PSD)的精度,考虑了活性炭孔壁面晶体粗糙度对结果的影响。在传统NLDFT基础上,结合吸附壁面碳原子的密度分布,推导出改进NLDFT,预测了氩在光滑及具粗糙碳晶体表面的吸附平衡,并根据87.3 K、氩在活性炭上的吸附平衡数据,在由两种NLDFT确定了不同孔径的理论等温线核后,由寻优函数确定活性炭在0.35~12 nm区间的PSD。结果表明,以改进的NLDFT预测活性炭的PSD时,确定的活性炭孔径呈连续分布,预测平衡数据的相对误差小于10%;传统NLDFT确定的孔径在1 nm处出现断点,最大的预测相对误差范围达45%。改进NLDFT能较准确预测氩在具有粗糙晶体碳表面活性炭的PSD。 相似文献
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介绍了球磨机平衡球级配的概念和钢球的磨损规律。在此基础上进行了平衡球级配的理论推导和修正,得到了平衡球级配的分布函数公式;并将推导所得函数的级配计算结果与流行的平衡球级配数据进行对比,二者结果几乎完全一致。 相似文献
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在DFT-B3LYP/6-31G*水平下,求得3,6二硝基胍基-1,2,4,5-四嗪(DNGTz)二聚体势能面上9种优化几何构型和电子结构.用基组叠加误差(BSSE)和零点能(ZPE)校正,计算了分子间相互作用能,二聚体分子间最大相互作用能为-62.24 kJ/mol.由自然键轨道(NBO)分析揭示了分子间相互作用的本质.对优化构型进行振动分析,并基于统计热力学求得温度200.0~800.0K从单体形成二聚体的热力学性质变化.结果表明,二聚主要由强氢键所贡献,而结合能不仅取决于氢键.二聚体Ⅰ、Ⅲ、Ⅳ、Ⅴ和Ⅶ的二聚过程在200.0K均能自发进行,表明二聚体Ⅰ、Ⅲ 、Ⅳ、Ⅴ和Ⅶ在室温可以稳定存在. 相似文献
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用径向分布函数法对三种不可石墨化碳结构的研究 总被引:1,自引:0,他引:1
本文应用广角X射线散射径向分布函数(RDF)法对三种典型的不可石墨化碳的结构及其随温度的转化进行了研究。在使用“去负法”对RDF进行截尾效应校正时,对Kaplow等的方法作了修正,发展成为“小r区降零过正法”,由自编的计算程序得到了不可石墨化碳的RDF,结果较为满意。由RDF曲线取得的基本结构参数是表征不可石墨化碳结构带本质性的基本数据。研究表明,在被测定的三种不可石墨化碳中,除主要为sp~2杂化键的石墨层片结构外,还存在着显著含量的sp~3杂化轨道碳一碳键。这说明,具有四面体结构的碳一碳交联键将芳香结构的层片状分子彼此联接,以及这些碳原子以层片内部缺陷处的sp~3杂化的间隙原子形式,存在于这三种不可石墨化碳中。其中,聚丙烯腈(PAN)基碳纤维在原子空间排布上受到原丝纺丝过程中拉伸张力的影响,而碳黑则受缺陷原子及层面皱折的制约,玻璃碳则由于乱带型碳网骨架的存在,形成了多微孔、低密度的结构特征。 相似文献
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为了探究吡嗪类缓蚀剂对铜的缓蚀机理,对比研究4种缓蚀剂的吸附性能。采用基于密度泛函理论(DFT)的量子化学方法,研究了4种吡嗪类缓蚀剂分子的反应活性及其在Cu(111)面的吸附行为,结果表明:4种缓蚀剂分子的前线轨道均分布在吡嗪环上,且吡嗪环上的N原子为分子的反应活性中心;4种吡嗪类缓蚀剂分子均能与Cu原子发生化学吸附形成共价键,且吸附强度排序为2-氨基吡嗪(AP)> 2-氨基-5-溴吡嗪(ABP)> 2-甲基吡嗪(MP)> 吡嗪(PY);另外,缓蚀剂分子也可以通过静电相互作用与金属表面发生物理吸附。 相似文献
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Covering a wide range of bulk densities, density profiles for hard-sphere chain fluids (HSCFs) with chain length of 3,4,8,20,32 and 64 confined between two surfaces were obtained by Monte Carlo simulations using extended continuum configurationai-bias (ECCB) method. It is shown that the enrichment of beads near surfaces is happened at high densities due to the bulk packing effect, on the contrary, the depletion is revealed at low densities owing to the configurationai entropic contribution. Comparisons with those calculated by density functional theory presented by Cai et al. indicate that the agreement between simulations and predictions is good. Compressibility factors of bulk HSCFs calculated using volume fractions at surfaces were also used to test the reliability of various eauations of state of HSCFs by different authors. 相似文献
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The density functional theory, simplified by the local density approximation and mean-field approximation, is applied to study the surface properties of pure non-polar fluids. A reasonable long rang correction is adopted to avoid the truncation of the potential. The perturbation theory is applied to establish the equation for the phase equilibrium, in which the hard-core chain fluid is as the reference fluid and the Yukawa potential is used as the perturbation term. Three parameters, elk, d and ms, are regressed from the vapor-liquid equilibria, and the surface properties, including density profile, surface tension and local surface tension profile are predicted with these parameters. 相似文献
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在密度泛函理论(DFT)的B3LYP/6-31G^*水平上对一系列靛族染料化合物的几何构型进行优化计算:在获得基态稳定结构的基础上,应用含时密度泛函理论(TD-DFT)在相同水平下计算其电子吸收光谱,探讨了不同给电子基团和发色体系的延伸对电子吸收光谱的影响,得到了与实验基本一致的变化规律。结果表明,给电子能力的增强和发色体系的纵向延伸均使光谱产生一定红移,通过对前线轨道组成进行自然布居分析,揭示了靛族染料的发光均源自分子中HOMO-LUMO(П→П^*)电子跃迁。 相似文献
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The thermodynamic properties of 135 polybrominated dibenzothiophenes (PBDTs) in the gaseous state at 298.15 K and 1.013×105 Pa, are calculated using the density functional theory (the B3LYP/6-311G**) with Gaussian 03. Based on these data, the isodesmic reactions are designed to calculate the standard enthalpy of formation (ΔfH1257;) and the standard Gibbs energy of formation (ΔfG1257;) of PBDTs. The relations of these thermodynamic parameters with the number and position of bromine substituents (NPBS) are discussed, and it is found that there exist good correlations between thermodynamic parameters (including heat capacity at constant volume, entropy, enthalpy, free energy, ΔfH1257;, ΔfG1257;) and NPBS. The relative stability order of PBDT congeners is proposed theoretically based on the relative magnitude of their ΔfG1257;. In addition, the values of molar heat capacities at constant pressure (Cp,m) for PBDT congeners are calculated. 相似文献
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张现仁 《中国化学工程学报》2002,10(6):644-649
Density functional theory(DFT)is used to calculate adsorption of thane molecules in single walled carbon nanotubes,A comparison of DFT calculations and grand canonical ensemble Monte Carlo(GCMC)simulations is made first and the two methods are in good agreement.Adsorption isotherms and structures of ethane molecules inside the tubes have been studied by DFT for nanotubes of diameters 0.954, 2.719 and 4.077nm at 157K and ambient temperature,300K,By using the grand potential,the positions of phase transitions are exactly located,and the effect of temperature and tube diameter on phase transitions and adsorption is discussed.We found that lowering temperature and increasing the pore size of several nanometer is preferable for the ethane adsorption when temperature is in the range of 157K-300K and operating pressure reaches several MPa.Layering transitions and capillary condensations are observed at 157K in two larger pore diameters,while these phase transitions disappear or the hysteres is loops become very narrow at 300K. 相似文献
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随着电子计算机技术的飞速发展,密度泛涵理论(DFT)方法在研究分子的结构与性能方面的应用日益广泛。碳纳米管是一种新型的碳纳米材料。具有独特的物理化学性质。它在储氢等方面的性能更是引起了人们的极大兴趣。这里着重介绍DFT这一重要理论及其在碳纳米管性能研究中的应用。 相似文献