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于长丰 《光谱学与光谱分析》2012,32(8):2056-2060
提出了一种构造解析势能函数的新方法,由此得到了一种既适用于中性双原子分子又适用于带电双原子分子离子的解析势能函数。本文用八种基本类型的双原子分子——同核中性基态双原子分子Na2-X1Σ+g,同核中性激发态双原子分子C2-A1Πu,同核带电基态双原子分子离子He+2-X2Σ+u,同核带电激发态双原子分子离子N+2-B2Σ+u,异核中性基态双原子分子NaLi-X1Σ+g,异核中性激发态双原子分子BH-B1Σ+,异核带电基态双原子分子离子(BC)--X3Π,异核带电激发态双原子分子离子(CS)+-A2Π等共21个算例对势能函数进行了验证并与RKR (Rydberg-Klein-Rees)实验数据进行了比较,计算结果与RKR数据符合很好。 相似文献
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An algebraic method (AM) used to study the full vibrational spectra of diatomic systems, and an analytical formula used to calculate accurate molecular dissociation energies are applied to study the full vibrational spectra and molecular dissociation energies of some electronic states of homonuclear and heteronuclear diatomic molecules and diatomic ions. Studies show that the AM method and the analytical expression are reliable and economical physical methods for studying full vibrational spectra and molecular dissociation energies of diatomic electronic systems theoretically. They are particularly useful for those diatomic systems whose highlying vibrational energies may not be available. 相似文献
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Wei-guo Sun Xiu-ying Liu Yu-jie Wang Yan Zhan Qun-chao Fan 《Frontiers of Physics in China》2008,3(4):382-413
An algebraic method (AM) used to study the full vibrational spectra of diatomic systems, and an analytical formula used to
calculate accurate molecular dissociation energies are applied to study the full vibrational spectra and molecular dissociation
energies of some electronic states of homonuclear and heteronuclear diatomic molecules and diatomic ions. Studies show that
the AM method and the analytical expression are reliable and economical physical methods for studying full vibrational spectra
and molecular dissociation energies of diatomic electronic systems theoretically. They are particularly useful for those diatomic
systems whose high-lying vibrational energies may not be available.
相似文献
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本文使用分子轨道从头算方法,在HF/6—31G和MP2/6—31G“水平下,计算了小硅化物SiXm的平衡几何和谐振子振动频率。理论值和实验值的比较表明,对于SiHm分子,实验的键长位于HF键长和MP2键长之间,而MP2振动频率更接近于实验的振动;率。对于SiClm分子,无论是键长还是振动频率HF值和MP2值都比较接近。对于SiFm分子,处于这两类的中间情况。关联作用随着X原子的原子序数的增加而减弱。 相似文献
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本文较系统地简介了双原子分子振动能谱和离解能的研究历史、现状及若干研究方法,重点介绍了孙卫国等最近建立的研究双原子分子完全振动能谱的代数方法(AM)和计算双原子分子离解能的新物理公式。然后应用AM方法和离解能新公式对一批同核和异核双原子分子,以及双原子分子离子电子态的完全振动能谱和离解能进行了研究。结果表明,AM方法和新建立的离解能解析式相结合的理论方法对研究双原子分子及离子的完全振动能谱和离解能是行之有效的、简单经济的物理方法,为实验技术难以精确测量其高激发振动能级或离解能的双原子分子或离子体系提供了获得精确的完全振动能谱和体系离解能的一种理论新方法。 相似文献
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运用杂化密度泛函(B3LYP)方法,对NpFn(n=3~6)的分子结构特性进行了系统地研究.优化得到了各分子的平衡几何构型,计算了分子的振动频率,并进行了态密度和自然键价轨道(NBO)分析.讨论了不同芯电子相对论有效原子芯势(RECP)对计算结果的影响,分析了NpFn分子的成键,发现随着与Np结合的F原子数目增加,Np原子的5f与F原子的2p轨道能逐渐接近,成键依次增强,键长呈现出收缩的趋势.目前的计算结果与可行的理论和实验符合较好. 相似文献
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用神经网络反向传播算法计算了双原子分子的键长。采用二原子的Slater原子半径,Paul-ing电负性,在元素周期表中的主族数及周期数等作为特征变量,得到了神经网络的训练及预报结果。 相似文献
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Quantum chemical calculations of bond dissociation energies for COOH scission and electronic structure in some acids
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Quantum chemical calculations are performed to investigate the equilibrium C-COOH bond distances and the bond dissociation energies(BDEs) for 15 acids.These compounds are studied by utilizing the hybrid density functional theory(DFT)(B3LYP,B3PW91,B3P86,PBE1PBE) and the complete basis set(CBS-Q) method in conjunction with the 6311G** basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work.Comparisons between the computational results and the experimental values reveal that CBS-Q method,which can produce reasonable BDEs for some systems in our previous work,seems unable to predict accurate BDEs here.However,the B3P86 calculated results accord very well with the experimental values,within an average absolute error of 2.3 kcal/mol.Thus,B3P86 method is suitable for computing the reliable BDEs of C-COOH bond for carboxylic acid compounds.In addition,the energy gaps between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) of studied compounds are estimated,based on which the relative thermal stabilities of the studied acids are also discussed. 相似文献
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The dissociation energy and equilibrium bond length as explicit parameters are used to establish an improved five-parameter exponential-type potential energy model for diatomic molecules. We demonstrate that the five-parameter exponential-type potential is identical to the Tietz potential for diatomic molecules. It is observed that the improved five-parameter exponential-type potential can well model the internuclear interaction potential energy curve for the ground electronic state of the carbon monoxide molecule by the utilization of the experimental values of three molecular constants. 相似文献
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Ultrasoft pseudopotentials and projector augmented-wave data sets: application to diatomic molecules
We test several ultrasoft pseudopotentials (US-PPs) and projector augmented-wave (PAW) data sets, calculating the bond lengths, the atomization energies and the frequencies of the vibrational stretch modes of various diatomic molecules. The US-PPs and the PAW data sets are constructed with the same recipe and using the local density approximation or the Perdew, Burke and Ernzerhof generalized gradient approximation for the exchange and correlation energies. We study the dimers H(2), N(2), O(2), F(2), Al(2), Si(2), P(2), S(2) and Cl(2) and several monohydrides, carbides, nitrides and oxides of boron, carbon, nitrogen, oxygen, fluorine, aluminum, silicon, phosphorus, sulfur, chlorine, iron and nickel. We find that US-PPs and PAW data sets constructed with the same parameters provide almost equivalent results for the bond lengths and the vibrational stretch frequencies while, for some molecules, the PAW method is superior to the US-PP method for the calculation of the atomization energies. Our geometries and vibrational frequencies are compared with the results present in the literature and obtained by localized basis sets. It is found that the agreement is very good, with discrepancies comparable to those due to the use of different localized basis sets. 相似文献
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Molecular properties such as bond length, dipole moment, harmonic frequency, IR intensity, atomization energy, electron affinity and ionization potential of the selected diatomic molecules of astrophysical interest have been studied using hybrid density functional HF/DF B3LYP method. The consistency and convergence of the results have been tested with four basis sets from 6-311 + + G (2df, 2pd) to aug-cc-pVTZ with improved size and quality. Most of the results for dipole moment, harmonic frequency, IR intensity, electron affinity and ionization potential are new. The reported results agree well with theoretical and experimental data wherever available.Received: 28 March 2003, Published online: 12 August 2003PACS:
31.15.Ew Density-functional theory - 33.15.Ry Ionization potentials, electron affinities, molecular core binding energy - 33.15.Dj Interatomic distances and angles - 33.15.Fm Bond strengths, dissociation energies 相似文献
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使用先进的量子化学ab initio程序MONSTERGAUSS和各种基函数组,在较大的核间距内计算了锂-锂,氟-氟原子间的位能曲线。并采用组态相互作用(CI)方法计算了基态锂分子(Li2 1∑g+)和基态氟分子(F2 1∑g+)的平衡核间距及总能量。计算结果与其它理论和实验结果进行了比较。 相似文献
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J.G. Powles 《Molecular physics》2013,111(4):1161-1180
We have explicitly calculated the experimental scattering cross-section for homonuclear diatomic molecular perfect gases using virtually exact expressions for the scattering law. These recoil and detector corrections are illustrated for a series of molecules at various temperatures on various instruments. We have shown that the conventional Placzek corrections are quite inadequate for vibrating molecules and we propose a simple recipe which leads to readily calculable expressions which give good agreement with the ‘exact’ results even for nuclei as light as deuterium. This recipe can be generalized for use for almost any nucleus in any molecule and may be expected to materially improve the accuracy of structure determination in molecular gases and liquids. In particular it is found that the Debye-Waller coefficient is very dependent on the experimental parameters. The generalization to time-of-flight experiments is given in the following paper. 相似文献
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The intermolecular influence on dipole moment function is evaluated for O-H bond of t-butanol in different nonpolar solvents at temperatures ranging from 10° to 60°C employing IR band intensities of fundamental and first overtone bands. Two sets of dipole moment derivatives have been calculated corresponding to – and +- combinations of the transition moment matrix elements R10 and R20, the values for ++ and -+ combinations are equal in magnitude to those for - and +- combinations, respectively and opposite in signs. In general the dipole moment derivatives increase on lowering the temperature as well as with increasing molecular interactions with the solvent molecules. Dipole moment plots with dimensionless coordinate ξ [=(r-re)/re, where r and re are internuclear distances during vibration and at equilibrium, respectively] are reported for various systems considered. It is found that for +- combination the dipole moment maximum shifts to higher internuclear distances when polarisation of the solute molecules is increased by lowering of temperature or increase in molecular interactions between solute and solvent molecules. A reverse trend is observed for – combination.- The OH band of t-butanol vapor has been measured. 相似文献
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Electric flux distribution in photodetachment of heteronuclear diatomic molecular negative ion
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The photodetachment of a hetero-nuclear diatomic molecular
negative ion is studied by using a two-centre model. An analytic
formula is presented for the electron flux distribution of a
heteronuclear diatomic molecular negative ion. Taking HF- as
an example, we calculated the electron flux distributions of this
ion for various detached electron energies. The results show that
the electron flux distributions exhibit oscillatory structures,
which are caused by the interference effect between the two nuclei.
Besides, the laser light polarization also has a great influence on
the electron flux distribution. The oscillation amplitude is the
largest when the laser polarization is parallel to the z-axis;
when the laser polarization is perpendicular to the z-axis, the
oscillation almost vanishes. This study provides a new understanding
of the photodetachment of a heteronuclear diatomic molecular
negative ion. 相似文献
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The identification algorithm developed here for scale parameters of gradient elasticity combines solutions for a deformed heterogeneous composite fragment in a continuous one-dimensional model and for a diatomic chain in a discrete atomistic model. For the identification, the models are taken equivalent and the effective stiffnesses of equivalent composite fragments are compared. In the discrete model, only the nearest neighbor atoms interact and the interaction between dissimilar atoms are determined by a modified Lorentz-Berthelot rule. As a result, the effective stiffness of the discrete composite represented as a nonuniform atomic chain is found. The continuous model is a gradient one and takes into account nonlocal effects in the volume and adhesive properties of phase boundaries. The problem of determining the effective stiffness of a composite fragment is solved analytically in the one-dimensional approximation. The study is aimed to develop a procedure of identifying the scale parameters of gradient theories such that the parameters would be independent of the choice of potentials used in discrete modeling. On the example of modeling using the Morse and Lennard-Jones potentials, we propose an identification methodology invariant with respect to the choice of potentials. It is shown that the invariance is provided if the potentials in discrete modeling are coincided in the vicinity of equilibrium points. It is demonstrated that for unambiguous determination of the scale parameters of gradient elasticity, it suffices to use the simplest two-parameter potentials approximating any other potentials subject to equal equilibrium bond distances and equal second derivatives at the equilibrium point (i.e., force constants). An example of identifying the gradient elasticity parameters is presented for a two-phase W-Si composite. 相似文献
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Accurate studies on the full vibrational energy spectra and molecular dissociation energies for some electronic states of N_2 molecule 总被引:2,自引:1,他引:1
REN Weiyi SUN Weiguo HOU Shilin & FENG Hao . Institute of Physics College of Chemical Engineering Sichuan University Chengdu China . Institute of Theoretical Physics Xihua Normal University Nanchong China . Department of Physics China Oceanography University Qingdao China . College of Physics Sichuan University Chengdu China 《中国科学G辑(英文版)》2005,48(4)
1 IntroductionAccurate results of high-lying vibrational energies and molecular dissociation energy De of diatomic electronic states are very important for thermodynamics, molecular spec- troscopy, reactive scatterings, and the collision physics of ultracold atoms. For example, the binding energy of the highest bound vibrational state to the ground vibrational state determines the s-wave scattering length. This in turn determines the low- energy (pre- dominantly s-wave) atomic elastic-scatteri… 相似文献