激光溅射法生成碱金属杂氮原子团簇NaNn+和KNn+

以高纯氮气为载气和反应物,分别通过激光轰击NaF、NaCl、KF和KCl压制成的样品,生成了相应团簇NaN_n⁺和KN+n,得到了团簇质谱图。其中,发现了钠杂氮团簇NaN₂⁺、NaN₄⁺、NaN₅⁺、NaN₆⁺、NaN₈⁺、NaN₉⁺、NaN₁₀⁺、NaN₁₂⁺和钾杂氮团簇KN₂⁺、KN₄⁺、KN₆⁺、KN₈⁺。质谱分析表明,氮原子数为奇数的钠和钾杂氮原子团簇不容易生成,而氮原子数为偶数的钠杂氮原子团簇和钾杂氮原子团簇较容易生成,其离子峰的相对强度随氮原子数增加而降低。     

铬杂氮团簇CrN_n~+的生成及光解

将铬/氮化硼(Cr/BN)混合粉末经压片机制成直径为13mm、厚度为2~5mm的底物,然后在反射式飞行时间质谱仪上,以高纯氮气为载气,用激光轰击Cr/BN底物,生成了铬杂氮团簇CrN_n~+(n=2、4、6、8),得到其质谱图。用波长为266nm的激光对CrN_6~+和CrN_8~+进行了光解,获得其光解质谱图,探讨了铬杂氮团簇的组成。结果表明,生成的铬杂氮团簇中最稳定的团簇为CrN_8~+,这些团簇的组成依次相差2个氮原子,推测生成的铬杂氮团簇CrN+8由Cr~+和N_2构成。     

铜团簇/正己烷溶胶的光学特性研究

采用脉冲激光轰击浸于流动正己烷中的铜靶,获得铜团簇/正己烷溶胶。UV-V is表明,铜团簇/正己烷溶胶在199、215、219和226 nm处有四个主要吸收峰;荧光光谱表明,铜团簇最大和第二激发峰位于308 nm和273 nm,相应发射峰位于370 nm和385 nm;TEM显示铜团簇随其粒径从小到大呈递减分布,平均粒径为14.1 nm。     

氨水团簇H_2O(NH_3)_n(n=1～6)的红外振动光谱分析

本文对氨水团簇H2O(NH3)n(n=1～6)的各尺寸最稳定构型的红外振动光谱进行了研究,得到了谱峰的分布情况,指出了最强峰的强度变化以及所对应的分子振动类型。     

密度泛函理论研究金属镧离子的水合团簇

Y型分子筛具有许多工整均匀的孔道结构,经常作为酸催化剂、双功能助推剂和择形催化剂,被广泛应用于干燥、洁净过滤、吸附分离和催化等领域。工业生产中稀土Y型分子筛的制备一般选用稀土离子水溶液与NaY型分子筛通过离子交换置换制取,但稀土离子水合结构以及通过分子筛孔的微观机理仍不清楚。本工作采用密度泛函理论(DFT)在M06-2X-D3/def2-SVP计算水平下,La3+采用LANL2DZ赝势基组,采用SMD=water隐式溶剂模型研究了La3+水合团簇及其不同价态时的结构性质,对水合团簇结构尺寸、Mulliken电荷、结合能以及能量分解进行了分析。结果表明,La3+水合团簇结构柔性较大,并非大于某个水合数无法通过分子筛孔;随水合数目的增大,La-O(H2O)平均半径有着增大的趋势,La3+在水溶液中总是趋于更稳定的多水合团簇结构;La-O(OH-)形成的键能比La-O(H2O)强;在[La(H2O)n]3+水合数目小于等于9时,团簇结构中以静电为主导作用,其次是诱导作用和交换互斥作用,色散作用所占比例最小;当水合数目大于9时,诱导作用所占比例升高,静电作用所占比例降低。研究结果对于深入认识稀土水合结构和分子筛制备机理具有重要理论指导意义。     

应用ABEEM/MM研究Al(Ⅲ)离子水分子体系

采用高水平的从头算方法,对铝离子水分子团簇 Al3+-(H2O)n(n=1-6)在 MP2/6-31++G(d,p)水平下进行了结构的研究.采用了BSSE校正且在MP2/6-311++G(2d,2p)水平下对能量进行了计算,并运用原子-键电负性均衡浮动电荷模型(ABEEM/MM),确定了Al3+-H2O的参数,将Al3+-H2O参数应用于Al3+-(H2O)n(n=1-6)体系中,计算内容包括结合能和连续结合能等,所得结果和从头算的结果符合较好.     

微米级棒状氧化铝团簇体的合成及表征

以γ-Al₂O₃粉末及碳酸氢铵为原料,采用水热技术成功制备微米级棒状氧化铝团簇体,考察反应温度、反应时间、物料配比等因素对微米级棒状氧化铝团簇体形貌的影响,并应用XRD、NMR、TEM、FTIR、SEM、N₂吸附-脱附、吡啶吸附-脱附等技术分析其物化性质及结构。结果表明：当γ-Al₂O₃粉末与碳酸氢铵质量比为 1∶1.75、反应温度为140℃、反应时间为6h时,合成的微米级棒状氧化铝团簇体直径为5～15μm,该微米级棒状氧化铝团簇体由直径50～100nm、长0.5～3μm的棒状氧化铝交叉堆积而成,比表面积为300m²/g、孔容为0.67mL/g,具有双重孔分布,可几孔径分别为3.5nm和26nm,表面同时含有六配位铝离子、五配位铝离子和四配位铝离子。     

PdnB(n=11-19)催化剂的结构与稳定性的理论研究

为研究在工业化应用的新型、高效、环保、绿色催化剂。通过密度泛函理论对BPd_n团簇的几何结构进行理论研究。计算结果显示Pd_nB(n=11-19),当B原子掺杂在Pdn团簇中,n在11-19的基态几何结构,可通过在Pd_n团簇的基础上添加B原子得到,并且随着团簇尺寸n从11到12的增加,下环被逐个填充在n=13处形成十二面体结构。当掺杂B原子后,团簇的稳定结构是B原子位于五元环内部,并且与五元环在一个准平面,而它的次稳定结构B原子位于五元环的外部,并且外缀在三元环上。最终从Pd_nB(n=11-19)的E_B、?²E和E_T分析得出BPd₁₅,BPd₁₈是幻数团簇。     

铌酸锂晶体缺陷研究中的介尺度团簇演变

铌酸锂晶体中存在着丰富的缺陷结构，主要包括V_Li、Nb_Li⁴⁺、V_Nb以及V_O等点缺陷。缺陷的存在会在很大程度上影响铌酸锂晶体的性质，如压电、电光、铁电、光折变、非线性光学性质以及激光损伤阈值，进而影响声表面波、电光调制器、声光调制器、温度/压力/加速度传感器等器件性能。铌酸锂晶体中缺陷形成的主要过程可以归结为以O^2–为中心的介尺度团簇演变。明确铌酸锂晶体缺陷形成过程中的介尺度团簇演变机制对于缺陷的控制具有十分重要的意义。本文将从缺陷类型、形成能以及介尺度团簇模型研究铌酸锂晶体中缺陷的动态演变过程以及形成机制。最后分析铌酸锂晶体结构中缺陷导致的杂化、再杂化过程，同时考虑多种自由度的耦合，为铌酸锂晶体的缺陷控制、快速生长以及性能调控贡献力量。最后举例介绍分析铌酸锂晶体缺陷与性质、功能的关联关系。     

H2在Mo x S y 团簇上吸附解离的尺寸效应研究

浆态床加氢工艺可以处理不同来源的劣质重油、渣油,氢气的活化是重油加氢处理过程中发生的主要反应之一。钼基催化剂的分散性是影响重油加氢活性的关键因素。构建了Mo₇S₁₅、Mo₁₂S₂₆、Mo₁₈S₃₉、Mo₂₅S₅₄和Mo₃₃S₇₁团簇,利用密度泛函理论研究了团簇自身的稳定性、活性以及H₂在不同尺寸团簇上的吸附与解离过程。结果发现,在目前所建立的团簇中,其尺寸越小,结合能越低,最高占据分子轨道-最低未占分子轨道(HOMO-LUMO)能隙值越小,团簇稳定性越弱,活性越强。H₂在簇上的稳定吸附位点为边缘位点。随团簇尺寸增大,吸附能分别为-64.25、-34.60、-34.14、-7.20、-6.82 kJ/mol,吸附能绝对值减小,氢气分子与团簇的相互作用减弱,并且解离能逐渐增大,分别为13.76、33.14、53.64、60.75、64.47 kJ/mol。目前的结果表明,团簇尺寸越小,氢气的吸附解离越容易,显示出更高的活性。     

苯丙烯酸邻菲罗啉铕钇配合物的合成及荧光特性

在乙醇介质中，合成了标题化合物，测定了其组成，红外光谱及荧光光谱，结果表明，羧酸的羟基氧及邻菲罗啉中的氮原子均与稀土离子配位，铕钇配合物的荧光强度值高于铕配合物。     

Embedded cluster Δ-XANES modeling of adsorption processes on Pt

Full multiple scattering models of X-ray absorption near edge spectra of Pt Janin clusters, with atop and bridge bound oxygen, were systematically improved by increasing the number of cluster atoms contributing X-ray photoelectrons from unity (limited-absorber model), to all six Janin cluster Pt atoms, and finally embedding the Janin cluster into a larger Pt reservoir with photoelectron contributions from all atoms. The simulated XANES of the adsorbate modified clusters were subtractively normalized to their respective clean clusters to yield Δ-XANES signatures. The sequential analysis of previously published limited-absorber model, and the isolated and embedded all atoms models provide insights concerning the relative contribution of surface vs. subsurface atoms to adsorbate induced ligand effects and charge compensation provided by the bulk lattice. Limitations to the application of Δ-XANES signatures to interpretation of Δ-XANES data obtained from an air-breathing fuel cell are discussed.     

Scaling up of cluster beam deposition technology for catalysis application

Many research works have demonstrated that the combination of atomically precise cluster deposition and theoretical calculations is able to address fundamental aspects of size-effects, cluster-support interactions, and reaction mechanisms of cluster materials. Although the wet chemistry method has been widely used to synthesize nanoparticles, the gas-phase synthesis and size-selected strategy was the only method to prepare supported metal clusters with precise numbers of atoms for a long time. However, the low throughput of the physical synthesis method has severely constrained its wider adoption for catalysis applications. In this review, we introduce the latest progress on three types of cluster source which have the most promising potential for scale-up, including sputtering gas aggregation source, pulsed microplasma cluster source, and matrix assembly cluster source. While the sputtering gas aggregation source is leading ahead with a production rate of ~20 mg·h^–1, the pulsed microplasma source has the smallest physical dimensions which makes it possible to compact multiple such devices into a small volume for multiplied production rate. The matrix assembly source has the shortest development history, but already show an impressive deposition rate of ~10 mg·h^–1. At the end of the review, the possible routes for further throughput scale-up are envisaged.     

Embedded cluster Δ-XANES modeling of adsorption processes on Pt

Full multiple scattering models of X-ray absorption near edge spectra of Pt Janin clusters, with atop and bridge bound oxygen, were systematically improved by increasing the number of cluster atoms contributing X-ray photoelectrons from unity (limited-absorber model), to all six Janin cluster Pt atoms, and finally embedding the Janin cluster into a larger Pt reservoir with photoelectron contributions from all atoms. The simulated XANES of the adsorbate modified clusters were subtractively normalized to their respective clean clusters to yield Δ-XANES signatures. The sequential analysis of previously published limited-absorber model, and the isolated and embedded all atoms models provide insights concerning the relative contribution of surface vs. subsurface atoms to adsorbate induced ligand effects and charge compensation provided by the bulk lattice. Limitations to the application of Δ-XANES signatures to interpretation of Δ-XANES data obtained from an air-breathing fuel cell are discussed.     

Simultaneous Synthesis and Densification of Titanium Nitride/ Titanium Diboride Composites by High Nitrogen Pressure Combustion

Composites of TiN/TiB₂ were synthesized by a combustion process of BN, Ti in a nitrogen atmosphere. The effect of the BN/Ti ratio and the nitrogen gas pressure on the synthesis of these composites was investigated. Dense TiN/TiB₂ composites with relatively high hardness and toughness were fabricated by combustion synthesis from Ti and BN under a nitrogen pressure of 4.0 MPa. The Vickers microhardness of the products obtained from reactants with a BN/Ti mole ratio of 0.11 increased with an increase in nitrogen pressure and had a maximum value of ∼25 GPa. Fracture toughness, K _IC, of the products increased from 3.1 to 5.9 MPa·m^1/2 as the BN/Ti ratio increased from 0.11 to 0.20. However, products formed under nitrogen pressures higher than 6.0 MPa exhibited circumferential macrocracks due to thermal shock.     

Combustion Synthesis of AlON–BN Composites under Low Nitrogen Pressure

Hexagonal boron nitride (hBN) and aluminum oxinitride (AlON) composites were synthesized by combustion reaction of powder mixtures of Al–B₂O₃–AlN systems under a low pressure of nitrogen gas (0.5 MPa). Explosive combustion reaction of Al–B₂O₃ systems under the same nitrogen pressure produced alumina, aluminum borate, AlN, and AlON depending on the binary mixing ratio, but no trace of BN phases could be identified. Most of the elemental boron product remained unreacted and amorphous. On the other hand, AlN addition as a diluent in the range of 15–30 wt% was effective in producing hBN phase and forming AlON–BN composites. In the composition range of the ternary mixture of Al, B₂O₃, and AlN, where significant BN formation was identified, the primary role of AlN was to react with B₂O₃ to produce BN and α-Al₂O₃. The temperature profile obtained during the combustion reaction by a thermocouple imbedded in the middle of the powder bed revealed that the initial nitridation reaction of aluminum metal provides the heat required for the combustion reaction, creating a state of a "chemical oven." The reaction product, α-Al₂O₃, reacted subsequently with AlN to produce AlON phases to give final AlON–BN composites. The combustion reaction was highly unstable and followed a mixed mode with a regularly reversing spinning mode for aluminum nitridation reaction in the surface region and an oscillatory mode for the BN formation reaction in the subsurface region.     

Alternating charge clusters of side chains: new surface structural invariants observed in calf eye lens gamma-crystallins

A detailed stereochemical analysis of the oppositely chargedside chains of amino acid residues on the surface of calf eyelens protein gamma-crystallin B has been carried out. The refinedstructural data of very high quality obtained at 1.47 Åresolution have been used. Charge–charge interactionswere considered to be valuable for all the charged oxygen andnitrogen atoms situated at distances, d, between 2.4 and 7.0Å. This means we consider short contact ion pairs as thosewith interchange distances 2.4 < d 4.0 Å and distantcontact ion pairs as those with distances 4.0 < d 7.0 Å.Hydrogen bonding of the charged atomic groups with the structuralwater molecules also has been considered. We have not lookedat the side groups of histidines which are charged only partiallyat neutral pH. Five clusters of charged side chains which werelarge enough were observed. The clusters are comprised of fourto six residues which compose 543% of the total charged residuesin the protein. The clusters contain from eight to 12 chargedatoms and look like the bent chains of oppositely charged atoms.All clusters are of plane geometry and their maximal lineardimensions are from 11 to 18 Å. The root mean square deviationsof charged atoms from the cluster plane varied from 0.63 to0.86 Å for four clusters and was only 1.85 Å forthe largest cluster. All clusters include a number of watermolecules situated on the cluster boundary and grouped nearthe cluster plane. It was shown that the amino acid sequencepositions of charged residues are conservative for all the proteinsof the gamma-crystallin family of vertebrates including fish,frog, mouse, rat, calf and human. The cluster properties werediscussed both in their functional aspect for gamma-crystallinsand in other aspects common for globular proteins. As a result,the alternating charge clusters should be considered as newlyrecognized surface structural invariants. The importance ofthe charged side chain clusters is claimed for the updated conceptof the protein surface.     

Effect of nitrogen concentration to the structural,chemical and electrical properties of tantalum zirconium nitride films

Tantalum zirconium nitride films with different nitrogen concentrations were deposited by reactive co-sputtering. Systematical material characterization was done to study the effect of nitrogen concentration to the ternary nitride films’ composition, microstructure, chemical and electrical properties. XRD and TEM showed that the microstructure of the films was mainly modulated by the Ta/Zr atomic ratio and nitrogen concentration, and amorphous structure formed in the nitrogen deficient films. XPS showed the chemical state of tantalum and zirconium atoms shifted systematically from metallic to ionic bonding state with the increasing of nitrogen. The stoichiometric ternary TaZrN films showed better conductivity than the binary TaN or ZrN constituents, because each tantalum atom contribute one excess d-orbital valence electron when the zirconium atom was substituted.     

Ab Initio Calculation of BN Generation from Boron and Nitrogen Oxides

Boron Nitride (BN) is one of the products produced in the burning of boron‐containing propellant. A possible reaction mechanism for the reactions of boron and nitrogen oxides (NO, NO₂, N₂O) has been studied using the G2MP2 method. The BN product can be formed in the reactions of B(⁴P) with NO, NO₂ and N₂O. Among these three reactions, B(⁴P)+NO₂ and B(⁴P)+N₂O are 181.42 kJ/mol and 160.92 kJ/mol more‐exothermic than the B(⁴P)+NO reaction. The barrier heights from intermediates to transition states are 64.85 kJ/mol and 111.75 kJ/mol for B(⁴P)+NO₂ and B(⁴P)+N₂O, respectively. However, in the reaction B(⁴P)+NO , the transition from intermediate to product (IM3→BN+O) is very endothermic by 420.70 kJ/mol. So B(⁴P)+ N₂O→BN+NO and B(⁴P)+NO₂→BN+O₂ are more likely reactions to generate BN than B(⁴P)+NO→BN+O.