含乙酰胺基链苯并菲盘状液晶分子的电荷传输性质与热力学性质

在密度泛函理论B3LYP/6-31G**理论水平上,计算含乙酰胺基链苯并菲衍生物分子的电荷传输性质和热力学性质。研究结果显示,该分子的空穴传输性能明显好于电子传输性能。在298.15 K时,该分子的标准摩尔生成焓和生成自由能分别为-2338.79 kJ/mol和-1756.27 kJ/mol。     

AuZn和AuAl分子基态与低激发态的势能函数与热力学性质

用密度泛函理论B3LYP方法计算研究AuZn和AuAl分子基态与低激发态的结构与势能函数,导出分子的光谱数据.结果表明,AuZn和AuAl分子基态分别为X²Σ和X¹Σ,基态与低激发态的势能函数均可用Murrell-Sorbie函数来表达.AuZn分子低激发态a⁴Σ的绝热激发能为43529kJ/mol,AuAl分子低激发态a³Σ的绝热激发能为19991kJ/mol.计算固体AuZn和AuAl的内能和熵时,近似以气体分子的电子能和振动能代替固体分子的内能,用电子熵和振动熵代替固体分子的熵.在此近似下,计算得到AuZn和AuAl基态与低激发态固态分子生成反应热力学性质与温度的关系. 关键词： AuZn和AuAl B3LYP 热力学性质 势能函数     

二氧化碳热力学性质的理论计算

用HF、MP2、QCISD和B3LYP四种方法,在6-311G* *基集合水平上对气态CO2(X1Σg)分子全优化,可直接得到热力学性质熵S和定压热容CP,在这四种方法中,B3LYP方法算得的结果与实验值最吻合,其相对误差分别只有0.00%和-0.15%;CO2分子的生成焓包含电子焓(为-393.31 kJ.mol-1)和核部分焓(为1.653 kJ.mol-1)两部分,其生成焓相对误差为0.37%.结果表明,所用理论方法计算气态CO2分子在1atm下的热力学性质是可行的.     

苯并菲衍生物盘状液晶分子的非线性光学与热力学性质

采用密度泛函理论在B3LYP/6-31G**理论水平,计算并研究苯丙炔（烯）酸酯苯并菲盘状液晶分子的偶极矩、非线性光学性质、电子光谱和热力学性质.结果显示,该分子表现出良好的非线性光学性质,其二阶和三阶非线性光学系数分别为10⁴和10⁶a.u.数量级.其最低能量跃迁吸收波长分别为460和474nm,对应π到π*的电子跃迁.在温度298.15 K时,苯丙炔酸酯和苯丙烯酸酯苯并菲衍生物分子的标准摩尔生成焓分别为-7317.06和-1052.68 kJ·mo1^-1,标准摩尔生成自由能分别为-6186.91和117.00 kJ·mol ^-1.     

两种新香豆素分子的热力学和光谱性质

使用密度泛函理论方法在B3LYP /6-31++G**理论水平对两种香豆素a和b分子的几何结构、光谱、热力学性质进行理论计算研究,并基于Tomasi的极化统一场模型(PCM)讨论溶剂效应。结果显示,香豆素a和b分子在气相中的最低能量吸收波长分别为352和355 nm,溶剂及其极性大小对香豆素a最低能量吸收波长影响很小,但在溶剂作用下香豆素b分子的最低能量吸收波长红移7-10 nm,溶剂的极性对该波长影响较小。298 K标准压力下香豆素a和b分子的气态标准摩尔生成焓 分别为-1373.171和-1310.805 kJ.mol-1,标准摩尔生成自由能 分别为-1064.043和-1035.849 kJ.mol-1,标准摩尔熵 分别为763.910和742.150 J.mol-1.K-1.     

烷氧链链长对吐昔烯电荷传输性质的影响

吐昔烯衍生物的盘状液晶分子,在有机电子材料领域被用作光导材料和载流子传输材料。使用电子转移的Marcus模型,在B3LYP/6-31G**水平上研究了5个含三条烷氧链(n=1,3,5,8,10)的吐昔烯衍生物分子的电荷转移性质。计算表明,电荷转移矩阵元t是影响分子电荷转移的主要因素。5个分子中,随烷氧链长度(n)增大,空穴、电子传输重组能的变化范围分别为16~19 kJ/mol和26~ 30 kJ/mol。空穴传输矩阵元t+减小超过4倍,空穴传输载流子迁移率μ+减小超过3个数量级。电子传输矩阵元t-增大幅度不大,电子传输载流子迁移率μ-增大2倍,表明烷氧链增长不利于空穴传输,有利于电子传输。     

烷氧链链长对吐昔烯电荷传输性质的影响

吐昔烯衍生物的盘状液晶分子,在有机电子材料领域被用作光导材料和载流子传输材料。使用电子转移的Marcus模型,在B3LYP/6-31G**水平上研究了5个含三条烷氧链(n=1,3,5,8,10)的吐昔烯衍生物分子的电荷转移性质。计算表明,电荷转移矩阵元t是影响分子电荷转移的主要因素。5个分子中,随烷氧链长度(n)增大,空穴、电子传输重组能的变化范围分别为16~19 kJ/mol和26~ 30 kJ/mol。空穴传输矩阵元t+减小超过4倍,空穴传输载流子迁移率μ+减小超过3个数量级。电子传输矩阵元t-增大幅度不大,电子传输载流子迁移率μ-增大2倍,表明烷氧链增长不利于空穴传输,有利于电子传输。     

Li-N-H储氢体系热力学性质的第一性原理研究

基于密度泛函理论的第一性原理方法, 系统地研究了Li-N-H储氢过程中各个化合物的晶胞参数、生成焓和化学反应焓. 结果发现优化后的晶格参数与先前的理论和实验研究符合得很好. 通过计算Li₃N, LiH, LiNH₂和Li₂NH在298 K的生成焓分别为-168.7, -81.0, -173.0和-190.8 kJ/mol, 进而计算得到整个储氢反应过程在T=298 K时反应焓为78.5 kJ/mol H₂, 这和他人计算得到T=300 K的结果75.67 kJ/mol H₂非常接近. 最后, 给出了储氢两步反应过程分别在T=298 K时的反应焓, 这些结果都与实验和他人理论计算得到的数据符合较好. 关键词： 第一性原理 热力学性质 Li-N-H 体系 反应焓     

全氟烃基联苯酯类液晶分子的光谱与热力学性质

使用密度泛函理论在B3LYP/6-311G*水平上计算研究了全氟烃基联苯酯类液晶分子的光谱和热力学性质。结果显示,分子的最低能量激发为HOMO→LUMO的p→p*跃迁, 对应的吸收波长值约为379 nm, 属于近紫外区。在298.15 K和标准压力下,标题化合物分子的生成反应为放热的自发过程,其标准摩尔生成焓与生成自由能分别为-4090.06和-3410.31 kJ.mol-1。     

全氟烃基联苯酯类液晶分子的光谱与热力学性质

使用密度泛函理论在B3LYP/6-311G*水平上计算研究了全氟烃基联苯酯类液晶分子的光谱和热力学性质。结果显示,分子的最低能量激发为HOMO→LUMO的p→p*跃迁, 对应的吸收波长值约为379 nm, 属于近紫外区。在298.15 K和标准压力下,标题化合物分子的生成反应为放热的自发过程,其标准摩尔生成焓与生成自由能分别为-4090.06和-3410.31 kJ.mol-1。     

有限长双壁碳纳米管的电子输运性质

基于Landauer公式，研究了有限长的非公度和公度双壁碳纳米管的电子输运性顾，结果表明 ，双壁管的几何结构对其电子输运性质有显著的影响：非公度的双壁碳管的电导随能量的不 同，既可以是弹道型的，也可以是非弹道型的；由armchair管组成的公度的双壁碳管的电导 随能量变化呈现快速的电导振荡，并且此快速振荡叠加在背景慢振荡上，而zigzag管组成的 公度双壁管的电导随能量变化只有快速振荡、没有规则的慢振荡背景. 关键词： 碳纳米管 电子输运性质     

EFFECT OF ANNEALING TREATMENTS ON DEFORMED POLY-ETHER-ETHER-KETONE (PEEK) FILMS

Physical aging of tapes of poly-ether-ether-ketone (PEEK) drawn at 120°C to 150% elongation and aged for 2 months at room temperature and at 120°C was analyzed. The physical aging was followed mainly with thermal analysis, transport properties, and Young's modulus. Moreover, a mechanical analysis, consisting of checking the length of tapes subjected to a constant load, during a thermal run gives additional information on the aging and on the capability to crystallize. The results are consistent with the formation on small regions in which segments of chains are closely packed.     

Effects of the strain relaxation of an AlGaN barrier layer induced by various cap layers on the transport properties in AlGaN/GaN heterostructures

The strain relaxation of an AlGaN barrier layer may be influenced by a thin cap layer above, and affects the transport properties of AlGaN/GaN heterostructures. Compared with the slight strain relaxation found in AlGaN barrier layer without cap layer, it is found that a thin cap layer can induce considerable changes of strain state in the AlGaN barrier layer. The degree of relaxation of the AlGaN layer significantly influences the transport properties of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures. It is observed that electron mobility decreases with the increasing degree of relaxation of the AlGaN barrier, which is believed to be the main cause of the deterioration of crystalline quality and morphology on the AlGaN/GaN interface. On the other hand, both GaN and AlN cap layers lead to a decrease in 2DEG density. The reduction of 2DEG caused by the GaN cap layer may be attributed to the additional negative polarization charges formed at the interface between GaN and AlGaN, while the reduction of the piezoelectric effect in the AlGaN layer results in the decrease of 2DEG density in the case of AlN cap layer.     

Molecular control over Ag/p-Si diode by organic layer

Electrical transport properties of Ag metal-fluorescein sodium salt (FSS) organic layer-silicon junction have been investigated. The current-voltage (I-V) characteristics of the diode show rectifying behavior consistent with a potential barrier formed at the interface. The diode indicates a non-ideal I-V behavior with an ideality factor higher than unity. The ideality factor of the Ag/FSS/p-Si diode decreases with increasing temperature and the barrier height increases with increasing temperature. The barrier height (φ_b=0.98 eV) obtained from the capacitance-voltage (C-V) curve is higher than barrier height (φ_b=0.72 eV) derived from the I-V measurements. The barrier height of the Ag/FSS/p-Si Schottky diode at the room temperature is significantly larger than that of the Ag/p-Si Schottky diode. It is evaluated that the FSS organic layer controls electrical charge transport properties of Ag/p-Si diode by excluding effects of the SiO₂ residual oxides on the hybrid diode.     

Theoretical study of the optical and charge transport properties in non-peripherally octasubstituted phthalocyanine–tetrabenzoporphyrin hybrids

The charge transfer rate of seven non-peripherally phthalocyanine–tetrabenzoporphyrin hybrids was investigated theoretically at the level of B3LYP/6-31+G(d,p) using density functional theory. The results showed that the hybrids are semiconductor molecules, which have a certain absorption in the visible region. The hole or electron transport capability of a non-peripherally substituted octamethyl phthalocyanine molecule is obviously better than that of phthalocyanine or non-peripherally substituted octafluorine, octamethoxy phthalocyanine molecules at 300 K, whereas the holes or electron transport capabilities of four non-peripherally substituted octamethoxy phthalocyanine–tetrabenzoporphyrin hybrids are basically the same. Overall, the hole transport capability of hybrids is superior to their electron transport capability. The charge transfer rate constant and the carrier mobility rate of three representative molecules using three methods, that is the long range-corrected functionals CHB-B3LYP and WB97XD, the metahybrid GGA M06-2X functional, are consistent with the use of the density functional B3LYP method.     

Modeling of the current lines in discontinuous metal/insulator multilayers

Discontinuous magnetic metal/insulator multilayers are formed of equally spaced layers of magnetic particles embedded in an insulating matrix. Their electronic transport properties result from spin-polarized electron tunneling and Coulomb blockade effect. The current-in-plane (CIP) and current-perpendicular-to plane (CPP) resistances change by several orders of magnitude when the thicknesses of the metallic or insulating layers are varied. Calculations of the shape of the current lines in these multilayers are presented. It is shown that pure CIP or CPP transport occur in these systems only when the CIP or CPP resistances are very different in magnitude. If the two resistances are of the same order of magnitude, then the measured transport properties in both geometries are a combination of CIP and CPP transport. Received 9 October 2001     

基于基液连续假设的大体系Cu-H2O纳米流体输运特性的模拟研究

分子动力学模拟是研究纳米流体的输运特性的重要手段, 但计算量庞大. 为研究能体现流动传热过程的大体系纳米流体的输运特性, 本文对基液采用连续介质假设, 将基液的势能拟合在纳米团簇的势能中, 大幅度减小了计算量, 使得大体系输运特性的模拟成为可能, 且模拟结果与多组实验结果吻合较好. 采用此方法模拟研究了速度梯度剪切对Cu-H₂O纳米流体颗粒聚集过程和聚集特性的影响, 进而对Cu-H₂O纳米流体在流动传热过程中的热导率和黏度进行了模拟计算, 定量揭示了宏观流动传热过程中不同的速度梯度、速度、平均温度和温度梯度对于Cu-H₂O纳米流体热导率和黏度的影响.     

氙等离子体输运性质计算

采用基于将Chapman-Enskog方法扩展到高阶近似的方法计算获得了温度范围在300—40000 K,不同压力条件下氙等离子体的黏性、热导率和电导率.热力学平衡条件下的计算结果与文献报道的实验和计算结果符合良好,验证了计算方法和结果的合理性与准确性.在此基础上,计算获得了电子温度(T e)不等于重粒子温度(T h)的热力学非平衡和化学平衡条件下氙等离子体的输运性质,并分析了输运性质随压力和热力学非平衡程度变化的原因.     

La0.67Pb0.33MnO3的磁性及输运特性

利用固相反应烧结法制备了La067Pb033MnO3单相多晶样品.研究了其结构、磁性及输运特性.结果表明，样品呈菱面相晶体结构，空间群为R3C，居里温度TC(=353K)非常接近TMI(=360K).在居里温度附近，发生铁磁-顺磁转变，导电特性由金属特征向半导体特征过渡.磁电阻在居里点达到极大值.当H=16T时，磁电阻的极大值为145%；当H=08T时，磁电阻的极大值为9%.输运性质表明，TTMI时 关键词： 磁电阻 输运特性 磁极化子 钙钛石