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用密度泛函理论方法BLYP/6-311++G(2df,2pd)对尿素分子的平衡几何构型进行了优化,并计算了该分子的谐力场.使用Wilson的GF矩阵方法,对尿素分子的振动基频进行了理论研究.根据振动频率的势能分布对此分子的振动基频进行了理论归属,计算的振动频率和能级指认均同实验结果吻合较好. 相似文献
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丙酮酸分子结构与振动光谱的密度泛函理论研究 总被引:1,自引:0,他引:1
用密度泛函方法BLYP、B3LYP和从头算Hartree-Fock(HF)方法在6-31G*基组水平上对丙酮酸分子的几何结构(甲基的重叠式和交错式两种构象)和振动光谱分别进行了优化和计算,并给出了各种频率所对应的红外强度及拉曼活性,对光谱进行了指认。结果表明:在丙酮酸分子的两种构象中,重叠式比较稳定*B3LYP计算得到的构型参数与实验结果比较一致;在振动频率的计算中,BLYP未标度力场所计算的非CH3伸缩振动基频预测值和实验值的平均绝对偏差为10.4cm-1;而HF标度力场的平均绝对偏差为17.9cm-1。说明两者的结果与实验观测频率比较吻合,但B3LYP的频率计算值偏差(38.3cm-1)较大。根据振动频率的势能分布和红外光谱强度对此分子的振动基频进行了理论归属。 相似文献
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去氢抗坏血酸分子振动光谱的理论研究 总被引:1,自引:0,他引:1
采用RHF, MP2, DFT(B3LYP)方法, 以6-311++G**为基组研究了去氢抗坏血酸分子(DHA)的平衡几何构型和振动光谱. 计算结果表明, 采用RHF, B3LYP以及MP2 方法优化得到的几何结构以及频率值是一致的. 采用B3LYP/6-311++G**计算了DHA分子平衡构型下的谐振动力场﹑振动频率和振动强度. 使用Wilson的GF矩阵方法对DHA分子进行了简正坐标分析, 依据所得的势能分布对DHA分子的振动基频进行了合理的理论归属. 相似文献
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2-氟-5-溴吡啶分子振动光谱的密度泛涵理论研究 总被引:3,自引:1,他引:2
用密度泛函理论方法B3LYP以及6-311++G(2df,2pd)基组对2-氟-5-溴吡啶分子 的平衡几何构型进行了优化并计算了该分子的振动谐力场。使用Pulay的标度方法 对理论力场进行了标度。采用Wilson的GF矩阵方法,根据标度后的理论力场进行了 简正坐标分析,对2-氟-5-溴吡啶分子的振动基频进行了理论研究,得到了势能分 布和红外振动频率。与红外频率的实验值相比较,理论频率的均方差为24 cm~(-1) 。此外,根据振动模式的势能分布对此分子的振动基频进行了理论归属,并对前人 的指认进行了修正和补充。 相似文献
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马钱子碱分子结构和振动光谱的密度泛函理论研究 总被引:2,自引:0,他引:2
用密度泛函理论B3LYP/6-31G*方法对天然药材马钱子中的生物碱马钱子碱的几何构型进行了优化,得到马钱子碱分子的平衡结构参数,并同实验结构进行了比较.计算了上述分子在平衡构型下的振动谐力场和振动基频.针对不同的振动模式,提出了相应的校正因子,并据此对计算频率进行了校正.理论计算和实验测定频率的平均误差为19.0cm-1.根据DFT计算的振动模式和IR光谱强度值对目标分子的实验振动基频进行了完善的和合理的指认和解释. 相似文献
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鸟嘌呤红外光谱的密度泛函理论研究──标度量子力学(SQM)力场处理 总被引:1,自引:0,他引:1
用密度泛函理论DFT(B3LYP)/6-31G*方法对鸟嘌呤分子的酮-胺式和醇-胺式异构体的几何结构、振动谐性力场和红外光谱进行了研究.理论力场由迁移自相关分子异胞嘧啶和咪唑的力常数标度因子进行标度.算得振动频率与鸟嘌呤的实验基质隔离IR光谱比较平均偏差对酮-胺式和醇-胺式分别为6.6和6.0cm-1.根据振动频率的势能分布和DFT计算的光谱强度值对鸟嘌呤分子的实验振动基频进行了理论归属. 相似文献
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Kolev TM Stamboliyska BA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(14):3127-3137
Geometry and vibrational spectroscopic data of benzil-d0 benzil-d10 and benzil-18O calculated at various levels of theory (RHF/6-31G*, B3LYP/6-31G*, BLYP/6-31G*) are reported. The theoretical results are discussed mainly in terms of the comparisons with infrared (4000-100 cm(-1)) and Raman (4000-50 cm(-1)) spectral data. The calculated isotopic frequency shifts, induced by the 18O- and d10-labeling, are in a good agreement with the measured values. A complete vibrational assignment was made with the help of ab initio force field calculations. The data thus obtained were used for reassigning some vibrational frequencies. The results of the optimized molecular structure obtained on the basis of RHF and the DFT calculations are presented and compared with the experimental X-ray diffraction for the benzil-d0 single crystal. It turns out that the best structural parameters are predicted by the B3LYP/6-31G* method. 相似文献
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本文用从头计算RHF和密度泛函B3LYP方法以及LanL2DZ,SDD和6-31G(d)基组计算了配合物M(Im)2X2 (Im=imidazole;M=Zn(Ⅱ),Pd(Ⅱ),Pt(Ⅱ);X=F,Cl,Br,I)的几何构型以及Far-IR和Raman振动频率。计算结果表明,对Zn(Ⅱ)配合物而言,B3LYP/6-31G(d)方法得到的几何参数与实验值吻合得最好,B3LYP/SDD次之。在计算Far-IR和Raman振动频率时,发现采用6-31G(d)基组,两种方法计算的结果差别不大。对LanL2DZ和SDD基组而言,对计算结果影响较大的是理论方法,基组影响甚微,个别的振动频率基组影响较大,相比较而言,SDD基组得到的结果更好一些。本文所使用的两种计算方法都能得到与实验值比较吻合的结果,而用从头计算RHF方法计算的结果与实验值更接近一些。在此基础上,预测了Pd(Ⅱ)和Pt(Ⅱ)配合物的Far-IR和Raman振动频率。 相似文献
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Torii H 《The journal of physical chemistry. A》2006,110(14):4822-4832
A time-domain method for calculating polarized Raman and two-dimensional infrared (2D-IR) spectra that includes the effects of both the diagonal frequency modulations (of individual molecules in the system) and the off-diagonal (intermolecular) vibrational coupling is presented and applied to the case of the amide I band of liquid N,N-dimethylformamide. It is shown that the effect of the resonant off-diagonal vibrational coupling and the resulting delocalization of vibrational modes is clearly seen as the noncoincidence effect in the polarized Raman spectrum and some spectral features (especially as asymmetric intensity patterns) in the 2D-IR spectra. The type of 2D-IR spectra (concerning the polarization condition) most appropriate for observing this effect is discussed. On the basis of the agreement between the observed and calculated band profiles of the polarized Raman spectrum, the time dependence of the transient IR absorption anisotropy is also calculated. The method of evaluating the extent of delocalization of vibrational modes that is relevant to the features of these optical signals in the time and frequency domains is discussed. The nature of the molecular motions (concerning the liquid dynamics) that are effective on the diagonal frequency modulations is also examined. 相似文献
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Tayyari SF Raissi H Ahmadabadi Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(12):2669-2682
The geometry, frequency and intensity of the vibrational bands of aluminum(III) Tris-acetylacetone Al(AA)3 and its 1,3,5-(13)C derivative were obtained by the Hartree-Fock (HF) and Density Functional Theory (DFT) with the B3LYP, B1LYP, and G96LYP functionals and using the 6-31G* basis set. The calculated frequencies are compared with the solid IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes. Most computed bands are predicted to be at higher wavenumbers than the experimental bands. The calculated bond lengths and bond angles are in good agreement with the experimental results. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Four bands in the 500-390 cm(-1) frequency range are assigned to the vibrations of metal-ligand bonds. 相似文献
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We have calculated optimal frequency scaling factors for the B3LYP/ 6-311+G(d,p) method for fundamental vibrational frequencies on the basis of a set of 125 molecules. Using the new scaling factor, the vibrational frequencies calculated with the triple-zeta basis set 6-311+G(d,p) give significantly better accuracy than those calculated with the double-zeta 6-31G(d) basis set. Scale factors were also determined for low-frequency vibrations using the molecular set of 125 molecules and for zero-point energies using a smaller set of 40 molecules. We have studied the effect on the calculated vibrational frequencies for various combinations of diffuse and polarization functions added to the triple-zeta 6-311G basis set. The 6-311+G(d,p) basis set is found to give almost converged frequencies for most molecules, and we conclude that our optimum scaling factors are valid for the basis sets 6-311G(d,p) to 6-311++G(3df,3pd). The new scale factors are 0.9679 for vibrational frequencies, 1.0100 for low-frequency vibrations, and 0.9877 for zero-point vibrational energies. 相似文献
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A computational study of the Au(+)Xe ionic system has been performed using newly developed coupled-cluster methods and relativistic model core potentials, with extra basis functions optimized to afford superior polarizabilities. Potential energy curves for the dissociation of Au(+)Xe were studied at different levels of theory, and molecular properties (bond length and harmonic vibrational frequency) were calculated. Wave functions were analyzed using the natural bond orbital method. The nature of bonding in this system is discussed. 相似文献
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Mukherjee V Singh NP Yadav RA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,81(1):609-619
The theoretical IR and Raman spectra of the 2,3,4-, 2,3,6-, 2,4,5- and 3,4,5-tri-fluorobenzonitrile molecules have been calculated by using the density functional method in the ground state. The rigorous normal coordinate analyses based upon both an empirical force field and quantum chemical calculations have been performed and the detailed vibrational assignment has been made on the basis of the calculated potential energy distributions (PEDs). A comparison of molecular geometries, atomic charges and vibrational fundamentals of these molecules has been reported. The effects of fluorination upon the geometries, atomic charges and vibrational frequencies of benzonitrile have been discussed. Several ambiguities and contradictions in the previously reported vibrational assignments have been clarified. In addition, the variation of Raman intensity with excitation frequency and with temperature has also been studied. 相似文献
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Krishnakumar V Ramasamy R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(4):673-683
The geometry, frequency and intensity of the vibrational bands of isoquinoline (IQ) and 8-hydroxyquinoline (8-HQ) were obtained by the density functional theory (DFT) calculations with the B3LYP functional and 6-31 G* basis set. The vibrational spectral data obtained from the solid phase mid and far FT-IR and FT-Raman spectra of IQ and 8-HQ are assigned based on the results of the normal coordinate calculations. The observed and the calculated spectra are found to be in good agreement. 相似文献
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Sevgi Haman Bayarı Basak Seymen Haci Ozısık Semran Saglam 《Journal of Molecular Structure》2009,893(1-3):17-25
The molecular geometry, the normal mode frequencies and corresponding vibrational assignments of methylphenidate in the ground state were performed by DFT/B3LYP level of theory using the 6-311++G(d, p) basis set. Harmonic vibrational frequencies were calculated. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The conformational stabilities and optimized geometrical parameters have been carried out with density functional theory with 6-311++G(d, p) basic set by the DFT/B3LYP method. The frequency calculations have been performed with DFT to study the vibrational properties and their dependence on the molecular conformation. 相似文献