共轭烯烃的共轭极化势

Based on the conjugated polarization theory,it is expressed as the conjugated polarizability potential （CPP）that the discrepancy between the average electrostatic energy of dipolar state and the electrostatic energy of non-polar state in the conjugated polarizability procedure for the conjugated alkenes. The correlation between CPP and the energy of ultraviolet absorption maximum,and the correlation between the energy of frontier molecular orbital obtained by ab initio calculation of quantum chemistry and the energy of ultraviolet absorption maximum have been carried out for the conjugated alkenes. Both correlation equations show a similar estimated precision. Further, the contribution of alkyl polarizability effect to the stability of dipolar state for the alkyl substituted alkenes with the effective polarizability effect index（PEI（ef））was quantified. Relating the above two parameters CPP and PEI（ef）to the energy of ultraviolet absorption maximum of the substituted alkenes in a two-parameter expression with a good prediction ability was obtained:v=1.1746+5.0187CPP-0.43204PEI （ef）,R=0.9995,s=0.0403,F=10853.28,n=23. The investigated results also indicate that it is less effective to reduce the energy of ultraviolet absorption maximum by means of increasing the alkyl substituent groups than lengthening the conjugated backbone chain in the conjugated alkenes.     

Dipole preserving and polarization consistent charges

A method for estimating dipole preserving and polarization consistent (DPPC) charges is described, which reproduces exactly the molecular dipole moment as well as the local, atomic hybridization dipoles determined from the corresponding wave function and can yield accurate molecular polarization. The method is based on a model described by Thole and van Duijnen and a new feature is introduced to treat molecular polarization. Thus, the DPPC method offers a convenient procedure to describe molecular polarization in applications using semiempirical models and ab initio molecular orbital theory with relatively small basis functions such as 6‐31+G(d,p) or without inclusion of electron correlation; these methods tend to underestimate molecular polarizability. The trends of the DPPC partial atomic charges are found to be in good accord with those of the CM2 model, a class IV charge analysis method that has been used in a variety of applications. The DPPC method is illustrated to mimic the correct molecular polarizability in a water dimer test case and in water‐halide ion complexes using the explicit polarization (X‐Pol) potential with the Austin model 1 Hamiltonian. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

NaX型沸石分子筛中吸附质分子结构与吸附热的关系

近年来,沸石分子筛结构与性能关系的理论计算研究工作愈来愈受到人们的重视[‘－0．人工合成的N     

The calculation of molar polarizabilities by the CNDO/2 method: Correlation with the hydrophobic parameter,log P

Results of molecular orbital (MO) calculations by the complete neglect of differential overlap (CNDO /2) method on 50 small molecules are reported. The summation of calculated atomic polarizabilities are equated with molecular polarizabilities, and these are compared with experimentally determined values. It is found that there is very good agreement between calculated and experimental molecular polarizability. This provides a reliable method for the determination of molecular polarizabilities for compounds for which experimental values are not known. The relationship between log P and polarizability is discussed and analyzed in terms of contributions from electronic components to the partitioning energy.     

A new form of electric-field-dependent basis functions for the calculation of electric polarizabilities and dipole moments

An ab-initio molecular orbital theory of electrical polarization is presented in which the molecular orbitals are written as linear combinations of atomic functions which depend explicitly on the strength of a uniform external electric field. The wavefunctions in the presence of such a field are determined using self-consistent field perturbation theory. It is shown that the use of field-dependent atomic functions provides an efficient technique for the calculation of electric polarizability tensors. Polarizability tensors and electric-dipole moments calculated using both a minimal and a split-valence-shell basis set are compared with experimental results. Both polarizability-tensor components and dipole moments are seriously underestimated at the minimal bases-set level. The split-valence basis approach yields substantially better results; the calculated values at this level are in reasonable agreement with the corresponding experimental values. The experimental ordering of isotropic polarizabilities for a set of small molecules is duplicated quite closely by both the minimal and the split-valence-shell calculations.     

Theoretical study on platinabenzene and mono- and difluorinated platinabenzenes: Structure, properties, and aromaticity

The electronic structures and properties of the platinabenzene and mono- and difluorinated platinabenzenes isomers have been investigated using hybrid density functional B3LYP theory. Basic measures of aromatic character were derived from structure, molecular orbital, and nuclear independent chemical shift (NICS). An energetic criterion suggests that ortho isomer of monofluorinated and F15 isomer of difluorinated platinabenzenes enjoy conspicuous stabilization. The polarizability and molecular orbital analysis are compatible with this result. NICS values calculated at several points above the ring center fail to give the result consistent with that based on relative energy, polarizability, and molecular orbital analysis. The atoms in molecules analysis indicates a correlation between NICS (1.0) and the electron density of the ring critical point (ρ_rcp) in monofluorinated platinabenzenes. There is a similar correlation in difluorinated platinabenzenes (except for F12 and F24 isomers) between NICS (0.5) and ρ_rcp.     

A natural linear scaling coupled-cluster method

It is shown that using an appropriate localized molecular orbital (LMO) basis, one is able to calculate coupled-cluster singles and doubles (CCSD) wave functions and energies for very large systems by performing full CCSD calculations on small subunits only. This leads to a natural linear scaling coupled-cluster method (NLSCC), in which total correlation energies of extended systems are evaluated as the sum of correlation energy contributions from individual small subunits within that system. This is achieved by defining local occupied orbital correlation energies. These are quantities, which in the LMO basis become transferable between similar molecular fragments. Conventional small scale existing molecular CCSD codes are all that is needed, the local correlation effect being simply transmitted via the appropriate LMO basis. Linear scaling of electronic correlation energy calculations is thus naturally achieved using the NLSCC approach, which in principle can treat nonperiodic extended systems of infinite basis set size. Results are shown for alkanes and several polyglycine molecules and the latter compared to recent results obtained via an explicit large scale LCCSD calculation. (c) 2004 American Institute of Physics.     

Theoretical model for the polarization molecular and Hückel treatment of PhosphoCyclopentadiene in an external electric field: Hirschfeld study

In this study we relate the Hückel method and molecular polarization of PhosphoCyclopentadiene (P-cyclopentadiene) with respect to the Cyclopentadienyl, and its consequent separation of charges of particular set of conjugated diene systems. The Hückel method and Molecular Polarization of P-cyclopentadiene is expressed as a function of the induced polarizability of Cyclopentadienylin an external electric field, presenting a technique to express the molecular polarizabilities and Hückel method of diene systems as a function of another in an external electric field, using local quantum similarity index (LQSI) based on the Hirschfeld partitioning in the framework of conceptual density functional theory, this index was introduced in the molecular polarization of cyclopentadienyl in an external electric field and in the secular determinant of the Hückel method applied to the Cyclopentadienylin order to express the molecular polarization and Hückel method as a function of P-cyclopentadiene using six local similarity index: Overlap, Overlap-Interaction, Coulomb, Coulomb-Interaction, Overlap-Euclidian distance and Coulomb-Euclidian distance.The topo-geometrical superposition approach (TGSA) was used as method of alignment, which allows us to obtain high results in the proposed LQSIs, this method to be a straightforward procedure to cope with the problem of relative orientation of the molecules when evaluating, developing a new technique that will allow us to study structural systems that differ in one atom in its structure, and proposing methodologies for future studies on a much broader range of systems in which the Hückel method and molecular polarization of two species that differ only in one atom in its structure can be approximated in this way.     

Between geometry, stability, and polarizability: density functional theory studies of silicon clusters Sin (n = 3-10)

The relationship between the polarizability, stability, and the geometry of small-size silicon clusters has been investigated by the density functional theory methods. Results obtained at local density approximation/Vosko-Wilk-Nusair and general gradient approximation/BLYP levels with polarized even-tempered basis set of quadruple zeta quality are presented and compared with those obtained by the B3LYP method, as well as with the ab initio results in recent literature. We have found that the polarizability is directly related to the size of the energy gap between symmetry-compatible bonding and antibonding molecular orbitals, but not necessarily to the size of the HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap. Furthermore, we have defined two structural parameters, namely, the averaged Si-Si distances and the standard deviation of the Si-Si distances, which were found to correlate remarkably well with the binding energy of the clusters and the HOMO-LUMO gap, respectively. These straightforward correlations would, therefore, provide a means to predict the physical properties, in particular, the polarizability and the stability, simply based on the structural information of the cluster.     

苯、萘、蒽芳烃分子稳定性和分子极化率规律的理论研究

苯、萘、蒽芳烃分子稳定性和分子极化率规律的理论研究桑兰芬，杨滢，杜秀华（长春光机学院基础部长春１３００１２）苏忠民，王荣顺（东北师范大学化学系长春１３００２４）关键词苯，分子极化率，同系物本文以苯、萘、蒽等最简单的单、稠环芳烃为例，对其体系稳定性变化...     

Maximum overlap symmetry molecular orbitals in conjugated systems

The application of the maximum overlap symmetry orbital (MOSO) method to conjugated systems is discussed briefly. The MOSO method can be employed to construct not only the symmetry orbitals and the molecular orbitais in alternant conjugated systems, but also the symmetry orbitais in non-alternant systems. It is shown that under the Hückel approximation the matrix MM⁺ can be written out directly from the molecular skeleton and may be treated by using chemical graph theory. Because the matrix MM⁺ of a system can be regarded as the Huckel matrix of a smaller system, the maximum overlap symmetry molecular orbital (MOSMO) calculation results can be easily obtained from those of the smaller systems. For homonuclear conjugated systems and for systems in which two kinds of atom appear altemantly, the MOSMOs and the corresponding molecular orbital (MO) energies obtained by the MOSMO calculation are the same as the MOs and the MO energies calculated by the Hückel molecular orbital method.     

Analytic calculations of vibrational hyperpolarizabilities in the atomic orbital basis

We present an analytic scheme for the calculation of pure vibrational contributions to linear and nonlinear optical properties such as the polarizability and the first and second hyperpolarizabilities. The formalism is fully expressed in terms of a perturbation- and time-dependent atomic orbital basis, using the elements of the density matrix in the atomic orbital basis as the basic variables. We calculate perturbed densities up to third order with respect to the electric field in accordance with the n + 1 rule, and the approach is therefore applicable for the calculation of pure vibrational contributions involving all vibrational coordinates in large molecular complexes. In the case of static electric fields, we therefore only need to calculate 19 response equations, independent of the size of the molecule. If we can determine the molecular energy and force field, the calculation of pure vibrational contributions to the nonlinear optical properties of the molecule is therefore a rather straightforward task. We illustrate the implementation by calculating pure vibrational contributions to the first and second hyperpolarizabilities of molecules containing up to 66 atoms using basis sets of good quality.     

Polarization and polarizability in extended one-dimensional organic materials

The modern theory of polarization in extended insulators is applied to one-dimensional models for conjugated polymers and charge transfer salts. Closed expressions for the dependence of the polarization on the site and bond energy alternations are presented for uncorrelated models, and results from exact real-space diagonalization are obtained for correlated models. Changes in polarization induced by lattice phonons or molecular vibrations are directly related to the intensity of infrared bands in the far and mid-IR, respectively. We model intensities by introducing linear electron-vibration coupling and show that coupling to delocalized electrons generates a combination band consisting of a lattice phonon and a molecular vibration. The displaced dipole operator is defined on a real-space basis allowing for the finite field calculation of linear polarizability in finite size systems with periodic boundary conditions. Size-consistency arguments are used to demonstrate that the resulting polarizability becomes exact in the thermodynamic limit, and numerical calculations demonstrate that this approach leads to reliable results that converge rapidly to the thermodynamic limit.     

含有噻唑生色团的Y-型有机分子的二阶非线性光学性质

采用密度泛函理论(DFT)B3LYP/6-31G*方法优化了一系列含有噻唑生色团的Y-型有机杂环分子的几何构型, 在此基础上结合有限场(FF)方法和含时密度泛函理论(TD-DFT)对分子的非线性光学(NLO)活性和电子光谱进行计算分析. 结果表明, 这些分子具有A-π-D-π-A(A: 受体, D: 给体)结构, 分子基态偶极矩、极化率和二阶NLO系数(β)随支链共轭桥的增长及生色团共轭效应的增大而增大. 同时, 该系列有机杂环分子的二阶极化率总的有效值(βtot)与其前线分子轨道能级相关, 分子的前线分子轨道能级差越小, βtot值越大.     

Molecular design of a π‐conjugated single‐chain electronically conductive polymer

This study demonstrates that single‐chain π‐conjugated systems can be made electrically conductive by modifying the molecular structures of both ends of the oligomers making up a polymer. That is, the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gaps of a fairly long polyyne‐type oligomer with appropriately modified molecular structures at both ends are found to be on the order of thermal energy by calculations using density functional theory (DFT) with B3LYP functionals. This result applies to molecular structures with characteristic bond alternations. The peculiar bond alternations are caused by competition between two effects of the bond alternations of the two mutually perpendicular π‐conjugated systems, which partially cancel each other out. It is probable that we can design one‐dimensional polymers with HOMO–LUMO gaps small enough to be conductive by combining the above‐mentioned oligomers with each other as monomer units in the polymer. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Electro-optical parameters of bond polarizability model for aluminosilicates

Electro-optical parameters (EOPs) of bond polarizability model (BPM) for aluminosilicate structures were derived from quantum-chemical DFT calculations of molecular models. The tensor of molecular polarizability and the derivatives of the tensor with respect to the bond length are well reproduced with the BPM, and the EOPs obtained are in a fair agreement with available experimental data. The parameters derived were found to be transferable to larger molecules. This finding suggests that the procedure used can be applied to systems with partially ionic chemical bonds. The transferability of the parameters to periodic systems was tested in molecular dynamics simulation of the polarized Raman spectra of alpha-quartz. It appeared that the molecular Si-O bond EOPs failed to reproduce the intensity of peaks in the spectra. This limitation is due to large values of the longitudinal components of the bond polarizability and its derivative found in the molecular calculations as compared to those obtained from periodic DFT calculations of crystalline silica polymorphs by Umari et al. (Phys. Rev. B 2001, 63, 094305). It is supposed that the electric field of the solid is responsible for the difference of the parameters. Nevertheless, the EOPs obtained can be used as an initial set of parameters for calculations of polarizability related characteristics of relevant systems in the framework of BPM.     

Innenrücktitelbild: Developing Conjugated Polymers with High Electron Affinity by Replacing a C?C Unit with a B←N Unit (Angew. Chem. 12/2015)

The key parameters of conjugated polymers are lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels. Few approaches can simultaneously lower LUMO and HOMO energy levels of conjugated polymers to a large extent (>0.5 eV). Disclosed herein is a novel strategy to decrease both LUMO and HOMO energy levels of conjugated polymers by about 0.6 eV through replacement of a C C unit by a B←N unit. The replacement makes the resulting polymer transform from an electron donor into an electron acceptor, and is proven by fluorescence quenching experiments and the photovoltaic response. This work not only provides an effective approach to tune the LUMO/HOMO energy levels of conjugated polymers, but also uses organic boron chemistry as a new toolbox to develop conjugated polymers with high electron affinity for polymer optoelectronic devices.     

Developing Conjugated Polymers with High Electron Affinity by Replacing a CC Unit with a B←N Unit

The key parameters of conjugated polymers are lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels. Few approaches can simultaneously lower LUMO and HOMO energy levels of conjugated polymers to a large extent (>0.5 eV). Disclosed herein is a novel strategy to decrease both LUMO and HOMO energy levels of conjugated polymers by about 0.6 eV through replacement of a C? C unit by a B←N unit. The replacement makes the resulting polymer transform from an electron donor into an electron acceptor, and is proven by fluorescence quenching experiments and the photovoltaic response. This work not only provides an effective approach to tune the LUMO/HOMO energy levels of conjugated polymers, but also uses organic boron chemistry as a new toolbox to develop conjugated polymers with high electron affinity for polymer optoelectronic devices.