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采用密度泛函方法,在B3LYP/D95*水平上对4种C12H12多面体分子的构型进行了全优化,计算了其振动频率及红外吸收强度,并模拟了它们的红外光谱图。采用统计热力学方法,在200~600K的温度范围内,分别计算了立方烷生成这4种C12H12多面体分子的热力学函数。由计算得到的自由能得知,这些分子都比立方烷稳定,因此从热力学角度来说,既然立方烷能够合成,这4种C12H12多面体分子也应该能够合成出来。根据计算得到的热力学函数及立方烷的生成焓,求出了这4种C12H12多面体分子的生成焓。 相似文献
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Coplanar poly-cage cubanes C8+4nH8 (n=1–5) have been studied using DFT method at B3LYP/D95** level of theory, vibrational frequencies of these molecules have been calculated at B3LYP/D95** level of theory and spectrums of these molecules have been simulated else, heats of formation of these molecules also have been estimated here. 相似文献
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The di-, tri- and tetra-cage coplanar cubanes have been studied at B3LYP/D95^** andMP2/D95^** levels, and their vibrational frequencies have been calculated at B3LYP/D95^** level. All of these species have no imaginary vibrational frequency, so that each of the molecules is a mini-mum at the potential energy hypersurface. Many properties of the molecules, such as geometries,heats of formation and the first ionization potentials, have been studied in this paper. 相似文献
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LIU Feng-Ling GUO Wei-Ling ZHAI Yu-Qing FENG Shuai 《结构化学》2005,24(7):745-751
1 INTRODUCTION In recent years, a great number of achievements have been achieved in the field of molecules with cage-like structures, such as fullerenes and poly- hedral hydrocarbons. Each of these molecules has only one cage, such as C60 and dodecahedrane. As is well known, every carbon atom can form four single bonds with other atoms. Since each carbon atom at the cage surface of the carbo-polyhedral molecule only forms three bonds with other carbon atoms, it may form the fourth singl… 相似文献
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采用量子化学中的DFT理论方法, 在B3LYP/6-311G*水平上全优化得到了不饱和类碳烯H2C=CLiCl的平衡结构。 结果表明, 不饱和类碳烯H2C=CLiCl只有2种平衡结构。 对这2种平衡结构之间相互转化的过渡态进行计算, 同时, 采用统计热力学及过渡态理论, 研究了2种平衡结构之间相互转化的热力学及动力学性质, 进而讨论了2种平衡结构在不同温度下的稳定性问题, 结果表明在所研究的100~600K温度范围内, 只有一种平衡结构能够存在。 在计算得到振动频率及吸收强度的基础上, 模拟了稳定平衡结构的红外光谱图。 相似文献
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LIU Feng-Ling WANG Jin-Shan PENG Ling 《结构化学》2005,24(11):1264-1270
1 INTRODUCTION Pagodane (Fig. 1) first synthesized[1] in 1983 has been studied by Prinzbach and coworkers for more than twenty years[2, 3]. Described as a waxy solid melting without decomposition and stable to at least 600 ℃ in gas phase, pagodane is interesting for its exotic structure and as an introduction to the family of substituted dodecahedranes[2]. Owing to its unu- sual structure, pagodane has provided experimenters and theorists with a challenge to characterize and cal- culate … 相似文献
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Using geometry optimization and DFT method at the B3LYP/6-31G* level of theory for C30H20, an equilibrium geometry is identified that has the form of polyhedral hydrocarbon with five carbon–carbon single bonds linking a dodecahedrane cage and a pentaprismane cage. Thus, this molecule is a tri-cage molecule with two pentaprismane cages and one dodecahedrane cage. Vibrational frequencies and the infrared spectrum are computed at the same level of theory. The heat of formation for C30H20 has been estimated in this paper. The heat of formation of C30H20 as well as the vibrational analysis indicates that this molecule enjoys sufficient stability to allow for its experimental preparation. 相似文献
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用密度泛函理论(DFT)和从头算(ab initio)方法,在B3LYP/6-31G、 B3LYP/6-31G*、 B3LYP/6-311G*和MP2/6-31G*水平上全优化计算了2,3,7,8-四氯苯并二英(2,3,7,8-TCDD)的几何构型、电子结构和振动频率,并用校正后的频率计算了298~1500 K的标准热力学函数,同时用半经验的PM3 SCF-MO进行了同样的计算,计算结果与实验值及文献值较好地吻合. 相似文献
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不饱和类卡宾H_2C=CLiF的结构及氢迁移反应的DFT研究 总被引:1,自引:1,他引:0
用量子化学中的密度泛函DFT方法,在B3LYP/6-311G~*水平上研究了不饱和类 卡宾H_2C=CLiF的结构。结果表明,只有1种平衡结构是稳定的。对稳定的平衡结构 ,找到了分子内氢迁移反应的过渡态,并计算了不同温度下不饱和类卡宾 H_2C=CLiF的平均寿命τ,在200 K时,τ = 7.9 d,在300 K仅为τ = 2.4 s。 相似文献
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DFT法研究3-羟基丙烯醛的双键旋转异构反应机理 总被引:2,自引:0,他引:2
利用密度泛函理论(DFT)分别在B3LYP/6-31G**和B3LYP/6-311++G**的计算水平上优化了基态3-羟基丙烯醛分子在双键旋转异构反应过程中的平衡态以及过渡态的几何构型,分析了反应过程中键参数的变化,计算了该反应的内禀反应坐标(IRC),发现在重排反应途径上存在一个四元环骨架的中间体.通过振动分析对平衡态和过渡态进行了确认,并得到了零点能.计算结果表明,基态3-羟基丙烯醛分子的双键旋转异构反应经过两步完成,第一步反应位垒稍高,第二步反应位垒较低,存在着发生重排反应的可能性. 相似文献
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Abdullah G. Al-Sehemi Mohrah Abdullah M. Al-Melfi Ahmad Irfan 《Structural chemistry》2013,24(2):499-506
The ground state geometries have been computed by using density functional theory (DFT) at B3LYP/6-31G*, B3LYP/6-31G**, and PCM-B3LYP/6-31G* level of theories. The highest occupied molecular orbitals (HOMOs) are delocalized on whole of the molecule and the lowest unoccupied molecular orbitals (LUMOs) are localized on the tricarbonitrile. The lowest HOMO and LUMO energies have been observed for Dye1 while highest for Dye4. The LUMO energies of Dye1–Dye4 are above the conduction band of TiO2 and HOMOs are below the redox couple. The absorption spectra have been computed in solvent (methanol) and without solvent by using time-dependant DFT at TD-B3LYP/6-31G*, TD-B3LYP/6-31G**, and PCM-TD-B3LYP/6-31G* level of theories. The calculated maximum absorption wavelengths of the spectra in methanol are in good agreement with experimental evidences. The maximum absorption wavelengths of new designed sensitizers are red shifted compared to parent molecule. The electronic coupling constant and electron injection have been computed by first principle investigations. The improved electronic coupling constant and electron injection revealed that new modeled systems would be efficient sensitizers. 相似文献
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多氰基立方烷生成热的DFT-B3LYP和半经验MO研究 总被引:5,自引:1,他引:4
运用密度泛函理论(DFT)B3LYP方法和半经验MO(MINDO/3,MNDO,AM1和PM3)方法系统计算了全部21种多氰基立方烷的生成热,首先,在DFT-B3LYP/6-31G^*水平下通过不破裂立方烷笼状骨架(亦即选择立方烷为参考物)的等键反应设计,精确计算了9种多氰基立方烷的生成热;发现B3LYP/6-31G^*结果分别地均与上述四种半经验MO方法求得的生成热之间存在良好的线性关系(相关系数均在0.9994以上),且以AM1生成热与B3LYP/6-31G^*计算值最为接近,其次,其它12种多氰基立方烷的精确生成热借助上述线性关系通过校正对应的AM1结果而获得,多氰基立方烷的生成热很高,且随-CN基数目的增加而线性地增大,表明它们属于极具潜力的“新一低高能炸药”而具开发价值。 相似文献
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Amareshwar Kumar Rai Ce Song Zijing Lin 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,73(5):865-870
An extensive exploration of the conformational space has been carried out to characterize all possible gas phase structures of leucine. A total of 324 unique trial structures for canonical leucine were generated by considering all possible combinations of single bond rotamers. All trial structures were optimized at the B3LYP/6-311G* level of the DFT method. A total of 77 unique and stationary canonical conformers were found. Further, 15 most stable conformers were reoptimized at B3LYP/6-311++G** level and their respective relative energies, vertical ionization energies, hydrogen bonding patterns, rotational constants and dipole moments were calculated. A single point energy calculations for leucine conformers have also been done at both B3LYP/6-311++G(2df, p) and MP2/6-311++G(2df, p) levels. The good agreement between our estimates of rotational constants for two most stable conformers and available experimental measurements supports the reliability of the B3LYP/6-311++G** level of theory for describing the conformational behavior of leucine molecule. The proton affinity and gas phase basicity were also determined. Using the statistical approach, conformational distributions at various temperatures have also been performed and analyzed. Vibrational spectra were also calculated. It is also observed that zwitterions of leucine are not stable in gas phase. 相似文献
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1INTRODUCTIONInrecentyears,agreatnumberofachievementshavebeenacquiredforthemoleculeswithcage-likestructures,suchasfullerenesandpolyhedralhydro-carbon.Pentaprismane,firstlysynthesizedbyEaton,OrandBranca[1]in1981,isatypicalpolyhedralhy-drocarbon.Owingtoitssymmetricalandstrainedstructure,manystudiesincludingMM2andMM3molecularmechanicscalculations[2,,semi-empiri-3]calMNDOandAM1molecularorbitalcalcula-tions[4],abinitioHFcalculations[5~7]andDFTcal-culation[8]havebeencarriedoutonit.Recen… 相似文献
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运用密度泛函方法,比较不同水平的基组(HF/6-311+G^*;B3LYP/6-31G^*;B3LYP/6-311+G^*)对具有D~6~h对称性的C~3~6分子进行构型优化的结果,并分析其几何结构、电子结构、稳定性等性质;采用基组B3LYP/6-31G^*对H@C~3~6,Li@C~3~6,Na@C~3~6,K@C~3~6分子进行构型全优化,分析了不同内嵌原子对其几何结构、电子结构、稳定性等性质的影响;首次在B3LYP/6-311+G^*水平上,对C~3~6H~6,C~3~6H~1~2,X@C~3~6(X=H,Li,Na,K)几何构型及电子结构进行研究并得到其稳定性规律。 相似文献
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FAN Jian-Fen② LU Yun-Xiang WANG Qiu-Xia WU Li-Fen SUN Yun-Peng 《结构化学》2005,24(4):413-418
Density functional theory (DFT) has been applied to study the enantioselective reduction of 3-morpholin-4-yl-l-phenyl-l-propanone with borane catalyzed by (S)-4-benzyl-5,5-diphenyl-l,3,2-oxazaborolidine at the B3LYP/6-31G* level. All molecular species involved in the four reaction steps have been fully optimized and the structural parameters are provided, and the micro process of reaction was also investigated. The catalyst-alkoxyborane adduct formed in step Ⅲ exhibits a B-O-B-N tetra-atomic ring. Reaction coordination calculations show that BH3 can react with 3-morpholin-4-yl-l-phenyl-l-propanone spontaneously, resulting in the need of 2 tool BH3 in the reaction. 相似文献