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Quantum-chemical techniques were applied to investigate a series of conjugated polymers: poly(3-octylthien-2,5-ylene-co-pyrid-2,6-ylene) (pl), poly[pyrid-2,6-ylenebis(3-octylthien-2,5-ylene)] (p2) and poly[pyrid-2,5-ylenebis(3-octylthien-2,5-ylene)] (p3) comprising alternating n-excessive 3-alkylthiophene and n-deficient meta- or para-linked pyridine moieties. Their ground state and excited state structures were optimized with density functional theory B3LYP method, and the optical properties were calculated by the time-dependent density functional theory (TD-DFT) and ZINDO/S methods. Their HOMO-LUMO gaps (An-L), the lowest excitation energies (Eex), ionization potentials (IP) and electron affinities (EA) were obtained by extrapolating those of the polymers to the inverse chain length equal to zero (1/n=0). The calculated results showed that the decrease of pyridylene content increased the HOMO level and decreased the LUMO level while the para-linkage further contributed to it. The IP are in the order: p1〉p2〉p3 but EA are: p1〈p2〈p3. In addition, the decrease of the pyridylene content and the para-linked pyridylene in the backbone of the polythiophene resulted in a narrowed energy gap and bathochromic absorption and emission peaks.  相似文献   
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采用量子化学方法研究了一系列含π-富电子烷基噻吩和间位或对位连接的π-缺电子吡啶共聚物,p1,p2,p3。运用密度泛函B3LYP方法对其基态和激发态进行几何构型优化,并采用含时密度泛函TD-DFT 方法和ZINDO/S方法分别计算了其相应化合物的光谱性质。通过外推低聚物的能隙(△H-L),最低激发能(Eex),电离势(IP),电子亲和势(EA)至链长倒数为零(1/n = 0)得到相应高聚物的对应性质的相关数据。计算结果表明,拉电子的吡啶基团使EA提高,即相应提高了电子的传输和注入能力。此外,含较少的吡啶成分和其在主链中以对位连接使其能隙变得更小,并导致吸收峰和发射峰红移。  相似文献   
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采用密度泛函理论(DFT)的B3LYP方法对H2O在β-Si3N4(0001)面上的吸附进行研究,采用原子簇模拟β-Si3N4(0001)表面,在6-31G·水平上计算常温常压下H2O分子在β-Si3N4(0001)表面的吸附构型和吸附能及电荷变化,同时考察温度、压强及预吸附BH3对吸附体系的影响.结果表明:H2O分子通过H原子吸附在β-Si3N4(0001)面的N原子顶位时最有利;当温度为100 ℃,压强分别为3×105~10×105 Pa时,吸附能为189.59 kJ/mol,与常温常压体系相比,吸附能增加了57.19 kJ/mol,吸附后O-H键拉长,可能发生解离;在BH3修饰的β-Si3N4(0001)表面上,由于预吸附导致吸附能减少.  相似文献   
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Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential (IP) and electron affinity (EA) of 2,7- and 3,6-linked carbazole trimers, two conjugated oligomers with different linkages of carbazole, were studied by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional (B3LYP). The absorption spectra of these compounds were also investigated by time-dependent density functional theory (TD-DFT) with 6-31G* basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-linked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electron- accepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.  相似文献   
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