Density Functional Theory Study on the Adsorption of Dioxygen on Small Pt-Pd Clusters

1 INTRODUCTION The bimetallic nanoclusters are of standing inte- rest since they can exhibit catalytic, electronic and optical properties distinct from those of corre- sponding pure nanoclusters[1～4]. Palladium and pla- tinum, well known for their catalytic properties, are often used as the catalyst in different fuel cells[5～8]. Several experimental results illustrate that for the oxygen reduction reaction (ORR), which is one of the primary reactions taking place in many fuel cells and…     

Theoretical Study on the Hetero-Diels-Alder Reactions between 3-Pyridinedithioesters and 1-Phenylsulfanylbutadiene

The mechanism, catalytic effect and solvent effect of the hetero-Diels-Alder reac- tions between 3-pyridinedithioesters and 1-phenylsulfanylbutadiene have been studied theoretically using density functional theory (DFT) at the B3LYP/6-31G(d) level. The results show that all of these reactions proceed in a concerted but asynchronous way. In some reactions the formation of C-S bond is prior to that of C-C bond and the opposite results are found in other reactions. The BF3 catalyst may lower the activation barriers by changing the energies of LUMO for 3-pyridine- dithioester. THF solvent has trivial influence on the potential energy surface of these reactions. With the BF3-catalyzed reactions, regioselectivity and stereoselectivity observed experimentally were predicted correctly by calculations and these results originate probably from C-H···F interaction in two transition states.     

DFT Calculations of the Ionization Potential and Electron Affinity of Alaninamide

Adiabatic and vertical ionization potentials (IPs) and valence electron affinities (EAs) of alaninamide in gas phase have been determined using density functional theory (BLYP,B3LYP,B3P86) methods with 6-311++G(d,p) basis set,respectively. IPs and EAs of alaninamide in solutions have been calculated at the B3LYP/6-311++G(d,p) level. Five possible conformers of alaninamide and their charged states have been optimized employing density functional theory B3LYP method with 6-311++(d,p) basis set,respectively.     

接枝改性PVDF基含氟聚合物

聚偏氟乙烯(PVDF基)含氟聚合物由于其独特的性能受到了广泛的关注.将功能化链段引入PVDF基含氟聚合物可以进一步提升其性能并拓展其应用领域.相较于物理共混法和直接共聚改性法,通过接枝改性法将功能化单体引入含氟聚合物的侧链具有更显著的优势,可便捷、高效地得到组成精确,结构可控的接枝共聚物.本文综述了通过活性自由基聚合(...     

热激活延迟荧光材料的光物理行为及性能预测

热激活延迟荧光(Thermally activated delayed fluorescence, TADF)材料由于三线态激子可通过反系间窜越(Reverse intersystem crossing, RISC)转换为单线态激子,在有机发光二极管(Organic light-emitting diodes, OLEDs)中理论上可达到100%的激子利用率而被广泛关注。但实验上开发设计高性能TADF材料较为复杂且研究周期较长,理论研究可以从本质上建立材料结构-性能的关系,预测材料的性质并提供一定的分子设计策略。本文围绕高性能TADF材料的开发,从发光原理出发,系统阐述了分子的设计策略及光物理参数如材料单-三线态能级差(Single-triplet energy gap,ΔE_ST)、系间/反系间窜越速率、吸收/发射光谱、辐射/非辐射速率等的计算原理、计算方法和研究进展。最后我们探讨了TADF材料理论研究面临的机遇和挑战,通过对TADF材料的理论研究综述和研究前景的展望,期待吸引更多的研究工作者,推动该领域的发展和突破。     

功能单体α-烯烃磺酸钠用于无皂乳液共聚合

用工业原料α-烯烃磺酸钠(AOS)作为功能单体与甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)进行了乳液共聚合,通过测定AOS与MAA的竞聚率,确定了适宜的聚合方式为连续加料法.使用5%AOS制备了高固含量(>60%)的胶乳,并与用十二烷基硫酸钠(SDS)作乳化剂时该体系的乳液共聚合进行了比较.AOS是影响乳液稳定性和胶粒大小的主要因素,当AOS含量为单体总质量的1%时可以得到固含量大于40%粒径小于100 nm的乳液;当AOS含量为5%时可以得到固含量大于60%的乳液.两种情况下胶粒粒径分散性均较窄,明显优于同样条件下用SDS制备的胶乳.使用1%AOS制得的胶乳静置1年后粒径及其分布基本保持不变.     

LixNi0.5Co0.5O2的态密度计算及电化学性能研究

>为获得综合性能更好的锂离子二次电池正极材料, 分析了Co掺杂对Li_xNiO₂电化学性能的影响. 采用密度泛函DFT理论对Li_xNiO₂和Li_xNi_0.5Co_0.5O₂的平均放电电压和态密度进行了计算. 同时, 用共沉淀法制备了Li_xNiO₂和Li_xNi_0.5Co_0.5O₂锂离子二次电池正极材料, 并对其进行了XRD结构分析和恒流充放电测试. 实验和计算结果表明: 随锂离子嵌入正极(电池放电), 电池的电压逐渐降低, 材料的态密度峰向低能量方向移动; 与Li_xNiO₂相比, Li_xNi_0.5Co_0.5O₂的电压平台相对较高(当0.25≤x≤0.5), 而且在Li^＋嵌/脱时, Li_xNi_0.5Co_0.5O₂的结构变化相对较小; Co离子的掺入, 减小了NiO₆八面体的畸变度, 使材料的电化学稳定性得以提高. 在钴掺杂镍酸锂体系中, NiO₆和CoO₆具有相互的稳定作用.     

Encapsulations of La@C82 and La2@C80 inside single-walled boron nitride nanotubes

Possibility of encapsulations of metallofullerenes inside single-walled boron nitride nanotubes (BNNTs) is studied by using first-principles calculations. We find that both La@C₈₂ and La₂@C₈₀ can be exothermically encapsulated inside the (17, 0) and (14, 7) BNNTs. The minimum diameters of exothermically encapsulating both La@C₈₂ and La₂@C₈₀ inside BNNTs are predicated to be about 13.4 Å.     

2-(2,5-二羟基苯基)-5-甲基-2,5-二氢吡咯并[3,4]富勒烯的合成和电子光谱的理论研究

利用丙氨酸和2,5-二羟基苯甲醛所形成的亚胺叶立德与C₆₀发生1,3-偶极环加成反应, 合成并分离、纯化制备了一种新的C₆₀吡咯烷衍生物: 2-(2-5-二羟基苯基)-5-甲基-2,5-二氢吡咯并[3,4]富勒烯. 通过¹H NMR, FT-IR, UV-vis和元素分析确定了其结构, 研究了体系的电化学和荧光性质. 采用密度泛函的方法, 在B3LYP/6-31G水平上对分子的几何构型进行了优化, 得到稳定的几何构型; 运用INDO/S方法计算了化合物的电子光谱, 计算结果434.2 nm与实验值432.0 nm基本一致.     

Au2、Au3小团族分子的结构和势能函数

原子团簇的结构和性质研究是当今物理学和材料学中的一个热门课题,过渡金属团簇特别是Au团簇,由于其独特的物理和化学性质而被广泛地应用于催化反应、材料吸附[1-2]和光的吸收中[3]。近年来,人们用不同的理论方法研究金原子团簇。H儯kkinen等人利用GGA方法研究了中性和阴离Au2-10团簇的性质[4];Bravo-P啨rez等人采用从头计算的HF和post-HF方法研究Au2-Au6小团簇[5],这些计算结果与实验值相比,相差较大。由于金团簇电子结构的复杂性,对Au体系考虑旋—轨耦合和电子相关效应是很重要的,这种计算的不确定性对Au的影响比IB簇的其它金属团…