密度泛函理论研究BeSin(n=1-12)团簇的结构、稳定性与电子性质

运用密度泛函理论(DFT),考虑多种初始构型下的自旋多重态,在B3LYP/6-311G基组水平上研究BeSi_n(n=1-12)团簇的平衡几何结构、电子性质、振动光谱与极化率.结果表明:BeSi_n团簇在基态附近有许多能量非常接近的同分异构体,且BeSi_n团簇的基态结构绝大多数为立体结构.n=1时,体系的基态为自旋三重态,n≥2时,则为单重态.铍原子的掺入使得主团簇的电子性质发生了明显的变化,掺杂使得体系的化学稳定性降低.BeSi₃,BeSi₅,BeSi₇与BeSi₉是幻数结构.团簇中原子间的成键相互作用随n的增大而增强.     

(Ca3N2)n(n=1—4)团簇结构与性质的密度泛函理论研究

用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G^*基组水平上对(Ca₃N₂)_n(n=1—4)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的振动特性、成键特性、电荷特性和稳定性等进行了理论分析.结果表明,(Ca₃N₂)_n(n=1—4)团簇最稳定构型中N原子为3—5配位,Ca—N键长为0.231—0.251nm,Ca—Ca键长为0.295—0.358nm;N原子的自然电荷在-1.553e—-2.241e之间,Ca原子的自然电荷在1.035e—1.445e之间,Ca和N原子间相互作用呈现较强的离子性,Ca₃N₂和(Ca₃N₂)₃团簇有相对较高的动力学稳定性. 关键词： 3N₂)_n(n=1—4)团簇')" href="#">(Ca₃N₂)_n(n=1—4)团簇 密度泛函理论 结构与性质     

[VS4-Cun] (n=3-6) 簇合物成簇反应的51V NMR研究

在核磁管内模拟反应体系(NH₄)₃VS₄/Et₄NBr/CuBr/PPh₃在CH₂Cl₂溶液中生成 [VS_4^-Cu_n](n=3-6)簇合物的过程. 利用⁵¹V NMR技术对反应过程进行准原位的实时监测,研究[VS₄Cu_n](n=3-6)簇合物的成簇条件和机理以及配体对成 簇过程的影响. 本文还详细讨论了反应溶液中不同浓度的PPh₃对[VS_4^-Cu₄] 簇合物的⁵¹V NMR化学位移的影响.     

第一性原理对Al_mSi_n(m=1,2;n=1～6)团簇结构与性质的研究

本文运用第一性原理对Al_mSi_n（m=1,2;n=1～6）团簇的结构与性质进行了研究.在BLYP的水平上进行了结构优化和频率分析,得到了团簇的最低能量结构.同时计算和讨论了A1_msi_n团簇的束缚能、总能的二阶能量差分和分裂能以及费米能随原子数的变化.研究结果表明:Al_mSi_n团簇在m+n<4时的几何结构是平面结构,从4个原子开始转为空间的立体结构;除AlSi₃和Al₂Si₂团簇外,Al_mSi_n（m=1,2;n=1～6）团簇的束缚能随原子数增加而减小;分析A1_mSi_n（m=1,2;n=1～6）团簇的二阶能量差分和分裂能发现:在m+n=3,5时,团簇都出现较稳定的结构.     

(HMgN3)n(n=1–5)团簇结构与性质的密度泛函理论研究

利用密度泛函理论在B3LYP/6-311G^*水平上对叠氮化合物(HMgN₃)_n(n=1–5)团簇各种可能构型进行了几何优化,预测了各团簇的最稳定结构. 并对最稳定结构的成键特性、电荷分布、振动特性及稳定性进行理论研究. 结果表明:HMgN₃团簇最稳定结构为直线型;(HMgN₃)_n(n=2,5)团簇最稳定结构为叠氮基中N原子和金属原子相连构成Mg–N–Mg结构;(HMgN₃)_n(n=3,4)团簇最稳定结构为叠氮基与Mg原子相互链接形成的环状结构. 团簇最稳定结构中金属Mg原子均显示正电性,H原子均显示负电性,叠氮基中间的N原子显示正电性、两端的N原子显示负电性,且与Mg原子直接作用的N原子负电性更强. Mg–N键和Mg–H键为典型的离子键,叠氮基内N原子之间是共价键. 团簇最稳定结构的红外光谱分为三部分,其最强振动峰均位于2258–2347 cm^-1,振动模式为叠氮基中N–N键的反对称伸缩振动. 叠氮基在团簇和晶体中结构不变,始终以直线型存在. 稳定性分析显示,(HMgN₃)₃团簇相对于其他团簇更为稳定. 关键词： 3)_n(n=1–5)团簇')" href="#">(HMgN₃)_n(n=1–5)团簇 叠氮基 密度泛函理论 结构与性质     

密度泛函理论研究Hg与Auqn(n=1—6, q=0,+1,-1) 团簇的相互作用

采用密度泛函理论中的广义梯度近似对Hg与小团簇Au ^q_n (n=1—6, q=0, +1, -1)的相互作用进行了系统研究. 结果表明,除Au₅^+,-团簇外,前线分子轨道理论可以成功预测大部分Au _n Hg ^q 复合物的最低能量结构. Au_n团簇对Hg的吸附受团簇尺寸大小和团簇所携带电荷的影 关键词： 密度泛函理论 汞 金团簇 吸附能     

Cu13±团簇几何和电子结构的密度泛函研究

借助遗传算法结合Gupta原子间相互作用势.本文采用密度泛函理论系统研究了带电Cu₁₃^±团簇的基态与低激发态的几何结构和电子结构,并与中性Cu₁₃团簇的结果进行了对比.计算结果表明:对Cu₁₃ⁿ（n=0,±1）团簇,高对称性几何构型在众多异构中无能量竞争性优势,团簇基态结构皆为非紧致低对称性结构,对Cu₁₃找到一种新的低对称性最低能结构;带电明显影响团簇结构稳定性,带电Cu₁₃^±团簇与中性Cu₁₃团簇的结构稳定性序列显著不同;基态Cu₁₃ⁿ（n=0,±1）团簇具有磁矩最小化效应,而其高对称性结构则有较大磁矩;计算所得Cu₁₃团簇电离能及电子亲和势与实验结果相符.     

低温高背压氘团簇源特性研究

为了产生大尺度氘团簇用于与强激光相互作用研究，研制了低温高背压团簇源.利用瑞利散射法对团簇尺度与气体背压相关性和团簇的形成演变过程进行了研究.得到团簇尺度N_c随背压的指数变化关系为N_c∝P^2.89₀，当气体温度为80K，背压P₀为48×10⁵Pa时，氘团簇尺度N_c≈2630，并得到了团 关键词： 氘团簇 团簇源 瑞利散射 激光与团簇相互作用     

笼状Au$lt;sub$gt;20$lt;/sub$gt;内掺$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;13$lt;/sub$gt;($lt;i$gt;M$lt;/i$gt;=Fe，Ti)团簇磁性的密度泛函计算研究

采用密度泛函理论中的广义梯度近似方法,对M₁₃（M=Fe,Ti）以及M₁₃内掺Au₂₀团簇的几何结构和磁性进行了计算研究.结果表明：M₁₃和M₁₃内掺Au₂₀团簇的几何结构在0.006—0.05 nm误差范围内保持着I_h对称性.Fe₁₃团簇最低能态的总磁矩为44 μ_B,内掺到Au₂₀笼中后形成的Fe₁₃内掺Au₂₀团簇的最低能态总磁矩为38 μ_B,且Au原子与内掺Fe₁₃团簇之间存在着弱铁磁相互作用.Ti₁₃团簇在总磁矩为6 μ_B时能量最低,掺入Au₂₀笼后形成的Ti₁₃内掺Au₂₀团簇最低能态总磁矩是4 μ_B,内表面12个Ti原子与表面Au壳之间是弱铁磁相互作用,而与中心Ti原子之间是弱反铁磁相互作用.由于Au₂₀笼状外壳的影响,Fe₁₃内掺Au₂₀和Ti₁₃内掺Au₂₀团簇中Fe₁₃和Ti₁₃的磁矩比无金壳的Fe₁₃和Ti₁₃团簇的磁矩分别减少了6.81 μ_B和2.88 μ_B. 关键词： 几何结构 磁性 密度泛函理论     

(K3N)n(n=1,…,5)团簇结构与性质的密度泛函理论研究

利用密度泛函理论B3LYP方法,在6-311G*水平上对碱金属氮化物(K₃N)_n(n=1,…,5)团簇各种可能构型进行几何结构优化,预测各团簇的最稳定结构,并对其成键特性、电荷分布、振动特性及稳定性进行分析研究.结果表明,随着n的增大,(K₃N)_n(n=1,…,5)团簇的最稳定结构逐渐由平面结构向空间立体结构转变,(K₃N)₄、(K₃N)₅团簇为类似晶体的层状结构;团簇中N原子的配位数以5、6较多见;团簇中N原子的平均自然电荷为-1.608e,K原子的平均自然电荷为+0.550e,K-N键为较强的离子键;(K₃N)₄团簇有相对较高的动力学稳定性.     

Conductivity and applications of Li-biphenyl-1,2-dimethoxyethane solution for lithium ion batteries

The total conductivity of Li-biphenyl-1,2-dimethoxyethane solution(Li_xBp(DME)_(9.65), Bp = biphenyl, DME = 1,2-dimethoxyethane, x = 0.25, 0.50, 1.00, 1.50, 2.00) is measured by impedance spectroscopy at a temperature range from 0℃ to 40℃. The Li_(1.50)Bp(DME)_(9.65) has the highest total conductivity 10.7 m S/cm. The conductivity obeys Arrhenius law with the activation energy(E_(a(x=0.50))= 0.014 eV, E_(a(x=1.00))= 0.046 eV). The ionic conductivity and electronic conductivity of Li_xBp(DME)_(9.65) solutions are investigated at 20℃ using the isothermal transient ionic current(ITIC) technique with an ion-blocking stainless steal electrode. The ionic conductivity and electronic conductivity of Li_(1.00)Bp(DME)_(9.65) are measured as 4.5 mS/cm and 6.6 mS/cm, respectively. The Li_(1.00)Bp(DME)_(9.65) solution is tested as an anode material of half liquid lithium ion battery due to the coexistence of electronic conductivity and ionic conductivity. The lithium iron phosphate(LFP) and Li_(1.5)Al_(0.5)Ti_(1.5)(PO_4)_3(LATP) are chosen to be the counter electrode and electrolyte, respectively. The assembled cell is cycled in the voltage range of 2.2 V-3.75 V at a current density of 50 mA/g. The potential of Li_(1.00)Bp(DME)_(9.65) solution is about 0.3 V vs. Li~+/Li, which indicates the solution has a strong reducibility. The Li_(1.00)Bp(DME)_(9.65) solution is also used to prelithiate the anode material with low first efficiency, such as hard carbon, soft carbon and silicon.     

Phase transitions and electrical properties of CsH(SO4)0.76(SeO4)0.24 mixed crystals

The study by X-ray diffraction, calorimetry, vibrational and impedance spectroscopy of CsH(SO₄)_0.76(SeO₄)_0.24 new solid solution is presented. Crystals of this composition undergo two phase transitions at T = 333 and 408 K. The last one at 408 K is a superionic-protonic transition (SPT) related to a rapid [HS(Se)O₄⁻] reorientation and fast H⁺ diffusion. A sudden jump in the conductivity plot confirms the presence of this transition. Above 408 K, this high temperature phase is characterized by high electrical conductivity (7 × 10^t-3 Ω⁻ cm⁻¹) and low activation energy (E_a < 0.3 eV).     

基于光谱分析技术的宣纸用铝盐施胶沉淀剂作用机理研究

为了明确铝盐沉淀剂在书画宣纸表面施胶过程中的作用机理,利用Ferron逐时络合分光光谱、高场27Al 核磁共振波谱(27Al-NMR)以及衰减全反射红外光谱技术(ATR-FTIR)研究了明矾(Alum)、聚合氯化铝(PAC)及聚合硫酸铝(PAS)三种常用铝盐施胶沉淀剂的水解聚合铝形态、与胶料混合后在宣纸表面施胶时的铝形态分布变化。(1) Ferron逐时络合分光光谱和27Al-NMR分析表明,明矾及聚合硫酸铝的水解产物主要为单核铝Al(H₂O)3+₆(Al₁),AlSO+₄和多核铝[Al₃₀O₈(OH)₅₆(H₂O)₂₄]18+(Al₃₀);聚合氯化铝除Al₁,Al₃₀外,还存在笼式结构的多核铝[AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]7+(Al₁₃);(2)27Al-NMR分析表明,铝盐与明胶混合后单核铝、多核铝形态的共振峰强度均有所降低,结合ATR-FTIR分析结果可知,降低的各正价态水解聚合产物很可能与明胶微粒中羟基(-OH)或羧基(-COOH)产生了键合,形成了网状络合物,将原本带负电的明胶粒子转化为带正电的明胶粒子,促使明胶微粒沉淀在带负电的纤维表面,起到施胶沉淀剂的作用。施胶后,明胶胶原蛋白的羟基、一部分氨基和羧基与植物纤维表面的非离子区域的羧基能形成众多的分子间的氢键,提高宣纸抗水性。因此,Ferron逐时络合分光光度法、高场27Al-NMR及ATR-FTIR技术相结合可迅速判断各类铝盐沉淀剂在宣纸表面施胶过程中的化学形态变化, 是研究施胶机理的有效手段。     

Impedance studies on polyacrylonitrile–CuX2–DMSO (X=Cl, Br, CF3SO3) solid polymer electrolyte

A series of polyacrylonitrile–dimethylsulfoxide–CuX₂ (X=CF₃SO₃⁻, Cl⁻, Br⁻), films (foils) were prepared by means of the solution cast technique. The thickness of the foils was between 0.04 and 0.09 cm and they contained 70–80 wt.% of the solvent. Conductivities of the solid electrolytes were obtained from impedance measurements. The conductivity increases with the increase of the salt content up to 8 wt.%; at higher concentrations (>8 wt.%) the conductivity is more or less stable, and reaches, in the case of Cu(CF₃SO₃)₂ and CuCl₂, the level of ca. 10⁻³ Ω⁻¹ cm⁻¹ at room temperature. The foils based on the CuBr₂ show even higher conductivity, close to 10⁻² Ω⁻¹ cm⁻¹ at room temperature, a value comparable to that characteristic for liquid solutions. The temperature variation of the conductivity for all the systems studied is of the Arrhenius type. The activation energy, determined from linear plots lnσ=f(T⁻¹), is of the order ca. 14 kJ mol⁻¹ for the PAN/CuBr₂/DMSO and of ca. 21 kJ mol⁻¹ for the PAN/CuCl₂/DMSO and the PAN/Cu(CF₃SO₃)₂/DMSO systems.     

Structural evolution of Sc-containing zirconia electrolytes

A powder of nominal composition (ZrO₂)_0.886(Sc₂O₃)_0.104(Al₂O₃)_0.01 was synthesized by spray drying with the purpose of testing the performance of solid oxide fuel cells containing scandia-stabilized zirconia (ScSZ) as electrolyte. The phases resulting from calcination and sintering at different temperatures were investigated by XRD, impedance and Raman spectroscopy. At sintering temperatures of 1200–1400 °C nearly equal amounts of cubic and rhombohedral ScSZ were detected, whereas heat treatment higher than 1500 °C led to a cubic single-phase material. A preliminary reaction mechanism of phase formation is proposed with respect to the various results depending on heat treatment.     

Effect of branching in base polymer on ionic conductivity in hyperbranched polymer electrolytes

Novel hyperbranched polymer, poly[bis(diethylene glycol)benzoate] capped with a 3,5-bis[(3′,6′,9′-trioxodecyl)oxy]benzoyl group (poly-Bz1a), was prepared, and its polymer electrolyte with LiN(CF₃SO₂)₂, poly-Bz1a/LiN(CF₃SO₂)₂ electrolyte, was all evaluated in thermal properties, ionic conductivity, and electrochemical stability window. The poly-Bz1a/LiN(CF₃SO₂)₂ electrolyte exhibited higher ionic conductivity compared with a polymer electrolyte based on poly[bis(diethylene glycol)benzoate] capped with an acetyl group (poly-Ac1a), and the ionic conductivity of poly-Bz1a/LiN(CF₃SO₂)₂ electrolyte was to be 7×10⁻⁴ S cm⁻¹ at 80 °C and 1×10⁻⁶ S cm⁻¹ at 30 °C, respectively. The existence of a 3,5-bis[(3′,6′,9′-trioxodecyl)oxy]benzoyl group as a branching unit present at ends in the base polymer improved significantly ionic conductivity of the hyperbranched polymer electrolytes. The polymer electrolyte exhibited the electrochemical stability window of 4.2 V at 70 °C and was stable until 300 °C.     

A higher conductivity Bi2O3-based electrolyte

We have developed a Bi₂O₃ electrolyte doped with Dy₂O₃ and WO₃ (DyWSB) that exhibits a higher conductivity than that of 20 mol% erbia stabilized bismuth oxide (20ESB), thus, giving it the highest conductivity of any known solid oxide electrolyte. Electrical conductivity results of the Dy–W stabilized bismuth oxide system are presented. The dopants were selected based on their polarizability and its effect on structural stability and conductivity. At 800 °C, the conductivity of (BiO_1.5)_0.88(DyO_1.5)_0.08(WO₃)_0.04 is 0.57 S/cm (1.5 times as high as that of 20ESB), and at 500 °C, the conductivity is 0.043 S/cm (2 times as high as that of 20ESB).     

A Possible Generalization of Jaynes-Cummings Model with Degenerate Spectrum

We propose a generalized Jaynes-Cummings model (JCM) for three two-level atoms and three-mode radiation field with the interaction being H₁=λ(a₁⁺a₂⁺σ_1-σ_2-+a₂⁺a₃⁺σ_2-σ_3-+a₁⁺a₃⁺σ_1-σ_3-+H.C.). This model is characteristic of possessing partly degenerate spectrum. Some transition process of this system is calculated.     

Nontraditional approaches to the examination of molecular solutions

On the basis of quantum-chemical calculation of methane, methylaluminum and methylindium, it is shown that essentially the non-divided 2s²-electron pair of the carbon atom has the ability to take part in specific intermolecular interaction. Thermodynamic analysis of structural changes in solutions of the Al(CH₃)₃–In(CH₃)₃, Al(CH₃)₃–In(C₂H₅)₃ systems substantiated the formation of solvate structures in which four types of interaction were involved. It is shown that specific intermolecular interaction with the participation of pentacoordinated carbon atom is approximately twice higher than the energy of the hydrogen bond in liquid ammonia.     

HREELS investigation of CO and K coadsorption on Fe(110)

The coadsorption of CO and K on Fe(110) has been studied using HREELS. Three adsorption states of CO with distinct C-O stretch frequencies have been found. These states, which are occupied sequentially during the exposure to CO and named as ₁,₂ and ₃, have strong (₁), intermediate (₂) and weak (₃) interaction respectively between the adsorbed CO molecule and the coadsorbed K. The distance between the CO molecule and the nearest K neighbor is the shortest for the ₁ state and the longest for ₃. The distance for the latter is estimated to be larger than 6 Å.