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本文较为全面地综述了Gaussian-1,Gaussian-2(简称G1,G2)理论以及简化的G2(MP2),G2(MP3)理论,将其主要结果进行了比较分析。关于G2理论的应用,除了较为详细地综述了几年来理论在重现实验数据、评价实验数据、预测实验数据及研究化学反应途径等方面的应用外,还结合我们近期研究结果的主要结论讨论了该理论在研究等电子-等自旋,价层等电-等旋,等旋及非等旋化学反应的能量计算中的应用情况,以及该理论在预测化合物的标准生成焓方面的应用情况。 相似文献
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几种含芯电子相关能修正的G2和G2(ACI)方法 总被引:1,自引:1,他引:0
针对冻结芯电子近似,在MP2/6-311G(d,p)级别上对G2、MP2/6-311G(d)和MP2/6-311G(d,p)级别上对G2(QCI)方法进一步考虑了芯电子相关能修正,尝试建立了G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)方法。G2-l test set 的反应能量计算结果表明,这些方法进一步减小了经验修正量;G2(QCI/ful)和G2(QCI/fu2)也比G2(QCI)的总体精度有所提高;但G2(fu2)在G2基础上,总体精度没有改善。G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)计算G2-l test set反应能量的平均绝对偏差分别为5.11、4.74和4.81kJ mol-1,G2和G2(QCI)分别为5.09和4.97kJ mol-1. 相似文献
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Analysis of the Electronic Structure of 1-(4-Aminobutyl)-3-methylimidazolium Chloride via DFT Method
Density functional theory and natural bond orbital analysis are applied to study the microelectronic structural properties of 1-(4-aminobutyl)-3-methylimidazolium chloride(C_4NH_2C_1imCl). We obtain 48 stable cation conformers at the B3LYP/6-311++G(d, p) level of theory. When the Cl anion is located at different positions around the two stable cation conformers,optimization and frequency are calculated at the same level of theory, and seven stable C_4NH_2C_1imCl structures are obtained. Ion-pair association energies, natural population analysis(NPA) charges, and the second-order stabilization energies are also calculated. Results show that three energy-degenerated states are present in seven conformers. The calculated ion-pair association energy, NPA charges, and second-order stabilization energy values are the same as those with the same energy level conformers. Finally, H bond formation in the molecule is analyzed by the interactions of frontier molecular orbitals. The lone pair of N(11) atom in the amino group exhibits higher reactivity than that of the N(4) atom in the ring. 相似文献
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Ab-Initio studies applying the 3-21G, 6-31G and 6-31G** basis sets and also including the MP2 correction were carried out on H2NNH2, HNNH3 and the transition state molecule of the reaction H2NNH2=HNNH3. First, the geometry of the three molecules was optimized using the theoretical methods mentioned in the Hartree-Fock(HF) scheme. The energies of the molecules corresponding to RHF/6-31 G** geometries were subsequently calculated including electron correlation effects at the level of the second-order Moller-Plesset(MP2) perturbation theory. The vibrational frequencies, net charges and dipole moments were obtained from the theoretical calculations. The results of our ab-initio calculations indicate unambiguously that H2NNH2 is thermodynamically more stable than HNNH3. On the other hand, an isolated HNNH3 molecule once created would be rather stable since barriers for its unimolecular isomerization and decomposition are relatively high. Nevertheless, HNNH3 can be considered as an intermediate in chemical processes involving N2H4. This assumption has been supported by further calculation at higher level of theory. 相似文献