非晶态合金Co-Mn-B的电荷转移及其催化性质的DFT研究

为深入了解非晶态合金Co-Mn-B的电子及其催化性能,利用密度泛函理论(DFT)方法,在B3LYP/Lan12dz水平下,将原子簇Co2MnB2的十余种可能构型分别在二、四重态下进行全参数优化计算和频率验证,最后获得两种类型的稳定构型(三角双锥型和变形四方锥型),其中三角双锥构型均是以金属原子为两锥、一金属原子和双B原子位于三角平面。对这些稳定构型的电荷转移及其催化活性进行研究分析,结果表明:原子簇Co2MnB2稳定构型中电子主要由Mn原子向B原子转移,Mn原子的引入起到调变B原子的电子流向作用。金属Co、Mn原子在二、四重态下对HOMO、LUMO轨道的贡献大小不一样;Mn原子的饱和轨道比Co原子更富电子。原子簇Co2MnB2因空轨道易于接受反应物的电子而具有良好的催化性能;构型4(2)具有较好的催化加氢、固氮活性。     

团簇Co_xFe_yB_2的结构特点与磁学性质的密度泛函数理论研究

为了深入了解非晶态合金Co-Fe-B的结构特点以及磁学性质,利用密度泛函数理论(DFT)方法,在B3LYP/Lan12dz水平下,对团簇Co_2FeB_2和CoFe_2B_2的十余种可能存在的构型在不同重态下进行全参数优化计算和频率验证,共得到17种不同构型,分别是三角双锥型、戴"帽"三角锥型、四方锥型以及平面型。对这些稳定构型的结构特点以及磁学性质进行研究分析,结果表明:团簇CoFe_2B_2比团簇Co_2FeB_2更具有结构多样性,而且各化学键的配置更加均匀、合理;在两团簇各构型中,二、三、四重态下的Co原子的磁矩非常接近,Fe原子的磁矩也是如此,且Co和Fe原子对磁性的贡献均较高;单重态下的Co和Fe原子对磁性的贡献较低;Fe原子对磁性的贡献大于Co原子的。     

非晶态合金Ni-Fe-B体系成键及电子性质的理论研究

结合文献报道,Ni／Fe=1：1时非晶态合金Ni-Fe-B体系对某些加氢反应的催化活性和选择性较好,设计一系列Ni、Fe等比例的双硼原子簇Ni2Fe2B2的各种可能构型,利用DFT方法在B3LYP／Lanl2dz水平下进行全参数优化和频率验证。分析优化结果中知：原子簇Ni2Fe2B2单重态有四个稳定构型、三重态有三个稳定构型,三重态能量均低于单重态能量;Ni-B、Fe-B键间有强烈相互作用;Ni、Fe原子带负电荷,B原子带正电荷,电子从类金属向金属转移,类似于非晶态合金Ni-B、Fe-B、Co-B体系的电子行为。     

CoFe_2BP团簇的组成、电子及磁学性质的研究

根据各优化构型之间的能量差,首次从能量学视角提出一种定量计算团簇CoFe2BP各优化稳定构型组成比例的方法,同时对团簇的电子和磁学性质进行研究,得出:各优化构型中,四重态构型所占的组成比例最大且立体结构趋于多样化;B原子接受电子,P原子提供电子,B原子所带负电荷量与B原子和周围成键金属原子数呈负相关,各原子中所有价轨道均参与成键;Co原子的磁矩小于Fe原子的平均磁矩;受各构型稳定性的影响,Fe原子磁矩在二、四重态中分别呈"凹"、"凸"形变化,Co原子的磁矩变化相对比较平缓;多重度的改变会对Co、Fe原子的磁矩变化产生不同的影响,同时Co、Fe原子的磁矩与构型的立体结构息息相关。     

非晶态合金Co-P-B体系的组成和催化性质研究

利用团簇Co3PB模型来研究非晶态合金Co-P-B体系,从能量学视角对团簇Co3PB中五种稳定构型所占比例进行定量分析后,可知共有四种主要存在构型,按构型稳定性排序后,二、四重态构型随能量的升高呈交替排列样式。Co原子是催化反应的活性质点,此结论与实验结果相同。结合态密度图分析,在催化反应中,团簇Co3PB易接受反应物的电子,使反应物活化。     

团簇Ni3B2多重态热力学稳定性和磁学性质

为了探究团簇Ni_3B_2的热力学稳定性和磁学性质,基于密度泛函理论对多重态构型进行了优化运算,结果得到7种稳定存在的构型,其中三重态四种,五重态三种;通过对比优化构型的热力学参数及电子自旋情况得知:稳定性顺序依次为1~((5))1~((3))2~((5))2~((3))3~((3))4~((3))3~((5));并且向上自旋电子自旋轨道密度的分立降低了构型的稳定性;通过对电子自旋情况的进一步研究讨论得知:团簇Ni_3B_2的磁性主要由3d轨道贡献;此外,三重态的构型中存在Ni—B间分子轨道的解离,解离出的向上自旋电子分布在Ni原子周围,向下自旋电子分布在B原子周围。     

Ni Ti+催化环己烷脱氢机理的密度泛函理论研究

使用密度泛函理论(DFT)中的B3LYP方法对Ni Ti+催化环己烷的脱氢机理进行了系统的研究。得到了反应中所涉及到的优化几何构型和相关的几何参数,并绘制了相应的二重态和四重态势能面图。研究表明,Ni Ti+催化环己烷脱氢主要以同面脱氢为主,并且三次脱氢机理是相似的,主要产物是第一第二分子脱氢。     

非晶态合金Fe-B-P催化活性和磁性的理论研究

采用原子簇方法,对倍受关注的Fe基非晶态合金Fe-B-P的催化活性和磁性进行研究.通过合理设计可调Fe含量的系列原子簇FenBP（n=1～4）可能构型三十余种,利用密度泛函理论（DFT）分别在单、三重态下进行优化计算.在不同多重度下,对所确定的原子簇FenBP（n=1～4）最稳定构型的几何结构、能量、能隙差、费米能级和d轨道布局数进行分析,结果表明：多重度对原子簇FenBP（n=1～4）几何构型影响较大;三重态比单重态稳定且催化加氢活性较好,其中三重态的Fe3BP活性最好;单重态的磁矩明显低于三重态,其中单重态的Fe4BP磁矩最小,表现出软磁性.     

高岭土负载氧化铜脱除还原态砷的机制研究

为了研究高岭土负载氧化铜后对还原态砷的吸附机理,利用密度泛函理论(DFT)分别计算高岭土及高岭土负载氧化铜后对3种还原气氛下典型砷组分的吸附构型,通过比较分析,获得3种砷的化合物(As2,As4,AsH3)与高岭土-氧化铜形成的稳定构型,同时分析各构型的吸附能、Mulliken电荷转移、偏态密度(PDOS)及差分电荷密度。结果表明,高岭土负载氧化铜(CuO/kaolinite)对3种分子的吸附能明显降低,体现较强的化学吸附作用,As4的吸附效果最好;氧化铜在吸附过程中作为主要活性分子得到大部分转移的电子;在3种稳定的构型中出现强度较高的共价键与氢键。     

1,1,3,3,5,5-三螺环(1,5-二氨基四唑)环三磷腈的密度泛函理论

采用密度泛函理论(DFT)中B3LYP和B3PW91方法分别在6-31G*和6-31G**水平下对1,5-二氨基四唑取代的环三磷腈类化合物进行了分子设计和计算,得到该化合物的两种同分异构体,通过对其进行构型优化、振动分析、自然键轨道分析和Mulliken布居分析,得到两种构型都能稳定存在.由分子能量和前线轨道能级差判断...     

Electronic properties of bilayer AA-stacked zigzag nanographene ribbons

First-principles calculations within the generalized gradient approximation are employed to calculate the electronic properties of the bilayer AA-stacked zigzag nanographene ribbon. The AFM-AFM configuration (antiferromagnetic and antiferromagnetic configurations for the intralayer and interlayer spin arrangements, respectively) is predicted to be the most stable system. The interlayer interactions alter the band structure such as the modulation of energy dispersions, the generation of new band-edge states, and the state degeneracy. The energy gap is inversely proportional to the ribbon width. As compared with the monolayer zigzag nanographene ribbon, the density of states exhibits more asymmetric peaks, and some peaks at low energy are enhanced due to the state degeneracy. These predicted results can be identified by scanning tunneling spectroscopy (STS) or the measurements of optical spectra.     

Proximal effects of ultraviolet light absorbers and polymer matrix in the photostability of β-carotene

β-Carotene was used as a probe to investigate the protection offered by 2-ethylhexyl 4-methoxycinnamate, a photostabilizer, upon ultraviolet-A photodegradation. β-Carotene and 2-ethylhexyl 4-methoxycinnamate were arranged in two distinct macroscopic configurations (core/shell and homogenous) in solution with tandem and single cuvettes. 2-Ethylhexyl 4-methoxycinnamate was also combined with poly(methyl methacrylate) in solution to investigate the protective synergy between the photostabilizer and the polymer matrix. The choice of configuration played a more dominant role than the concentration of 2-ethylhexyl 4-methoxycinnamate in the degradation of β-carotene, with β-carotene remaining more stable in the homogeneous configuration. Changing configurations yielded different proximities of 2-ethylhexyl 4-methoxycinnamate to β-carotene; closing the proximity increased the potential close interactions (<1 nm) where transfer of excited state energy from β-carotene to 2-ethylhexyl 4-methoxycinnamate could occur resulting in increased photostability. The addition of poly(methyl methacrylate) had a negligible impact on the decay of β-carotene in both configurations.     

Analysis of the strong propensity for the delocalized diamagnetic π electronic structure of hydrogenated graphenes

The conformation and electronic structure of hydrogen-treated graphenes are investigated using the density-functional theory (DFT) method. We show that the overall energetics of the hydrogen chemisorption configuration can be analyzed with two energy components: the electronic pairing effect in the hyper-conjugated π electron network and the strain effect in the C–C bond at the boundary between sp³- and sp²-bonded regions. Some unpaired hydrogenation configurations can show magnetic ground states, but these were found to be unstable. The least strained paired configurations strongly favored the delocalized π electronic states. This suggests that appropriate annealing following a hydrogen plasma treatment of graphene can lead to a semiconducting state with a stable finite bandgap.     

外部热耦合复合精馏塔的经济性与可控性评价

外部热耦合复合精馏塔系统是一种新型的精馏塔系统,通过操作在不同压力下的两个精馏塔的精馏段和提馏段之间的热传递来提高热力学效率。根据精馏段和提馏段热耦合的相对位置不同,外部热耦合复合精馏塔系统可分为对称型和非对称型两种结构。为便于设计和实现,可用外部换热器替代外部热耦合得到简化的结构。本文以乙烯乙烷物系分离过程为对象,通过对外部热耦合复合精馏塔系统建立了静动态模型,采用四点控制的方法,对三种结构的外部热耦合复合精馏塔的经济性和可控性两方面做了分析,证明了非对称型优于对称型外部热耦合复合精馏塔。同时,对使用外部换热器简化外部热耦合结构的方法提供了理论依据和参考。     

Multivariate calibration of fourier transform infrared spectra for determining thiobarbituric acid-reactive substance content in palm oil

Fourier transform infrared (FTIR) spectra of palm oil samples between 2900 and 2800 cm⁻¹ and 1800 and 1600 cm⁻¹ were used to compare different multivariate calibration techniques for quantitative determination of their thiobarbituric acid-reactive substance (TBARS) content. Fifty spectra (in duplicate) of palm oil with TBARS values between 0 and 0.25 were used to calibrate models based on partial least squares (PLS) and principal components regression (PCR) analyses with different baselines. The methods were compared for the number of factors, coefficients of determination (R ²), and accuracy of estimation. The standard errors of prediction (SEP) were calculated to compare their predictive ability. The calibrated models generated three to eight factors, R ² of 0.9414 to 0.9803, standard error of estimation (SEE) of 0.0063 to 0.0680, and SEP of 1.20 to 6.67.     

工业废渣中重金属化学形态的分析测定

介绍了一种分析测定工业废渣中重金属的化学形态的方法：连续化学苹取法。测定结果表明，工业废渣中所含的重金属，有些形态属于不稳定结合态，有些则属于稳定结合态。水泥工业在处置利用工业废渣作水泥混合材时应尽可能地将其中的重金属由不稳定态转变为稳定态，以确保混合材水泥的安全使用。     

Multi-Stable Conductance States in Metallic Double-Walled Carbon Nanotubes

Electrical transport properties of individual metallic double-walled carbon nanotubes (DWCNTs) were measured down to liquid helium temperature, and multi-stable conductance states were found in DWCNTs. At a certain temperature, DWCNTs can switch continuously between two or more electronic states, but below certain temperature, DWCNTs are stable only at one of them. The temperature for switching is always different from tube to tube, and even different from thermal cycle to cycle for the same tube. In addition to thermal activation, gate voltage scanning can also realize such switching among different electronic states. The multi-stable conductance states in metallic DWCNTs can be attributed to different Fermi level or occasional scattering centers induced by different configurations between their inner and outer tubes.     

Total oxidation of methane over doped nanophase cerium oxides

The formation of solid solutions of cerium oxide with the oxides of calcium, manganese, or neodymium enhances the catalytic activity of cerium oxide for the total oxidation of methane, whereas solid solutions with lead oxide showed an opposite effect. Reasons for this are discussed in terms of oxygen vacancy concentrations and mobilities, local structure configurations, number of oxidation states of dopant, and electron transfer properties. The effects of increased oxygen ion mobility and a more beneficial local structure support the increased catalytic activity for the calcium- and neodymium-doped cerium oxide samples. In addition, a reduced energy for charge transfer from oxygen to cerium supports a higher activity for the calcium-doped sample. The activity data were fitted to an Arrhenius equation, and the apparent activation energies were found to be between 110 and 130 kJ/mol. The particle sizes and the BET areas of the samples were only little affected by the reactor runs, and none of the samples were subjected to phase changes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Water molecule adsorption on a titanium-graphene system with high metal coverage

Density functional theory and molecular dynamics were used to study the adsorption of a water molecule on a graphene layer modified with titanium at high metal coverage, with the Ti atoms located above the centers of the carbon hexagons. Two stable configurations for the titanium-graphene sheet were considered. One with one titanium atom per eight carbon atoms and another with one Ti atom per two C atoms. We found that the water molecule is adsorbed on both configurations, but it is dissociated in two different ways forming H, O and HO when the interaction is with the second configuration.     

应用先进控制实现环氧丙烷装置节能降耗

滨化集团东瑞化工有限公司的环氧丙烷装置原采用集散控制系统控制,为进一步对装置进行节能降耗,实施了先进控制。先进控制实施后取得了显著效果。先进控制投用率超过95%。环氧丙烷产量提高了1.03%,每吨环氧丙烷消耗蒸汽降低了0.0458t,同时操作平稳率大幅度提高。