共查询到18条相似文献,搜索用时 125 毫秒
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在不加对称性限制的条件下采用不同的半经验方法CNDO,INDO,MINDO/3,MNDO和Pm3对自由酞菁(H2Pc)进行几何构型最优化和电荷密度布居分析,并将所得结果与Am1方法以及X射线衍射和中子衍射数据的数据进行比较.结果表明只有从INDO方法得到的是桥式构型,而从CNDO, MINDO/3, MNDO,Am1, Pm3方法得到的都是键式构型.除INDO之外所有的这几种方法都对先前报道的几何构型扭曲给出进一步的支持证据.新近建立的半经验方法如MNDO,An1,Pm3等看起来更适合于用来研究大分子如酞菁及其类似物的几何构型扭曲和电荷分布极化等问题. 相似文献
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硝酸酯化合物生成热的分子轨道研究 总被引:5,自引:1,他引:4
用MINDO/3, MNDO和AM1三种SCF-MO方法, 在全优化分子几何构型的基础上, 系统地计算研究了32个硝酸酯化合物的生成热, 与实验值相比, MNDO计算结果偏大很多; MINDO/3计算值与凝聚相实验值符合较好, 由于克服了MNDO法过高地估算原子之间Van der Waals核排斥能的缺点, AM1法给出了较满意的结果: 与七个气态实验值之间存在良好的线性关系(相关系数为0.992), 其间的平均绝对差值和平均差值分别只有10.28和-1.01kJ/mol。 相似文献
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含苯并五元环方酸衍生物的二阶非线性光学性质的理论研究 总被引:5,自引:0,他引:5
利用从头算HF/6-31G*方法对用苯并五元环取代的方酸衍生物体系SQ1~SQ15进行几何构型优化和电子结构计算. 以优化后的构型为基础, 应用ZINDO方法计算电子光谱. 同时应用从头算CPHF/6-31G*方法和半经验FF/AM1, FF/PM3, FF/MNDO等有限场方法计算了分子的二阶非线性光学系数βμ. 研究几何结构、电子结构和前线分子轨道能与βμ之间的关系, 为设计性能优良的有机非线性光学材料提供理论指导, 并对这四种计算方法的结果进行了比较. 相似文献
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用AM1、MNDO和INDO半经验方法研究了异质富勒烯C 相似文献
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Al6(OH)18(H2O)6的结构及成键方位的从头算及密度泛函分析Ⅰ 总被引:2,自引:0,他引:2
用半经验的CNDO、INDO、ZINDO/1、PM3、AM1方法,RHF法STO-3G、STO-3G*、STO-6G、STO-6G*、3-21G、6-31G水平的量子化学从头算及RB3LYP/3-21G、B3LYP/6-31G水平的密度泛函方法,对三水铝石有利生长基元Al6(OH)18(H2O)6的几种可能结构进行了理论计算,分析各种方法的能量效应,确定了最优结构(Al6(OH)18(H2O)6-[Al).在此基础上,兼顾效率因素,选择半经验的CNDO、INDO、ZINDO/1方法,用RHF/STO-3G水平的量子化学从头计算对Al6(OH)18(H2O)6-[A]进行几何优化,与相关体系的实验结构参数进行比较. 相似文献
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异质富勒烯C58BN的结构与光谱研究 总被引:3,自引:0,他引:3
用AM1、MNDO和INDO半经验方法研究了异质富勒烯C58BN各异构体的结构、稳定性和电子光谱.所有这些半经验方法给出了相似的稳定性顺序.结果表明,在6-6位置取代的异构体是最稳定的,异构体的稳定性随杂原子间距离的增加而降低;与C60相比,硼氮杂富勒烯C58BN具有较低的前线轨道能级差、较小的电离势和较低的稳定化能.C58BN很可能具有与C60分子相似的反应活性,易发生亲核反应,但比C60更易失去电子形成正离子.以AM1优化构型为基础,利用INDO/CIS方法计算了各异构体的电子光谱. 相似文献
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CNDO/2一级近似法CNDO/2-FA)是一种值得推荐的方法.此法从Hückel理论所得的密度矩阵出发,构成第一个Fock矩阵,对角化并得到新的密度矩阵后,即转向最后结果的计算.由于略去了自洽迭代,可节省数倍的计算量.已从几何构型、力常数、解离能、电离势、质子亲合势、转动位垒、前线轨道能量等多方面进行考察,一级近似结果皆与自洽结果很相近,仅电荷分布稍不满意.MNDO的一级近似则不可用。 相似文献
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The electronegativity, the inductive parameter, and the mesomeric dipole moments of substituents depend on the electronic
structure characteristics of organic molecules calculated by the CNDO/2, INDO, MINDO, MINDO/3, MNDO, and AMI methods. It is
shown that the electronegativity as well as the inductive and mesomeric characteristics of atomic groups may be estimated
by semiempirical quantum chemical methods. 相似文献
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G. N. Dolenko A. L. Litvin V. P. Elin O. Kh. Poleshchuk 《Russian Chemical Bulletin》1991,40(2):345-352
A set of correlation equations which relate the experimental values of the shifts of the E K lines (E=S, P, Cl) for various classes of E-containing compounds to the values of the effective charges of the atoms of E determined from quantum-chemical calculations by the CNDO/S, CNDO/2, INDO, MINDO/3, and MNDO methods in the minimal basis and the CNDO/S method in an expanded basis has been obtained. It has been established that the INDO method in the minimal basis is best for calibrating the values of (E K) on the basis of the values of the effective charges of the atoms, while the CNDO/2 method and the INDO in the expanded basis are practically unsuitable for determining the values of the effective charges of S and P atoms.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 403–410, February, 1991. 相似文献
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N. P. Glinskaya I. P. Gloriozov I. E. Nifant'ev Yu. A. Ustynyuk 《Russian Chemical Bulletin》1993,42(5):810-817
Energies, geometries, and electronic structures of structural isomers of 4,4,8,8-tetramethyl-4,8-disila-3a,4,4a,8-tetrahydro-sym-indacene as well as some transition states for the intramolecular metallotropic rearrangements of these compounds were calculated using the semiempirical quantum-chemical INDO and MNDO methods. The applicability of the MINDO/3, INDO, and MNDO methods for describing l-silyl derivatives of cyclopentadienes was tested on model compounds R3SiC5H5, where R is Me or H.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 859–865, May, 1993. 相似文献
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Semiempirical (MNDOC, MINDO/3, AM1, and MNDO) and ab initio (STO-3G and 4-31G basis sets) calculations on the relative stabilities, structures, and dipole moments of the 8 theoretically possible tautomeric forms of pyrazolone are reported. It is shown that MNDO + CI and MINDO/3 predict that 5-hydroxy pyrazole, 3-hydroxy pyrazole, and 2-pyrazolin-5-on are the most stable. These results correspond to the known experimental data. Of all used quantum chemical methods, the MINDO/3 results for the dipole moments of the investigated tautomers are in best agreement with the known experimental data. The electronic excitation energies were calculated using the CNDO/S-CI method. The results are in good agreement with the experimental UV spectra. 相似文献
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A formalism has been developed to treat hydrogen-bonded A—H…?B systems within the CNDO /2 and the MINDO /3 methodologies. In this formalism the interactions are divided into three distinct classes; those between (a) two hydrogen-bonded atoms, (b) one hydrogen-bonded and non-hydrogen-bonded atom, and (c) two non-hydrogen-bonded atoms. The last class of interactions is treated solely by the existing CNDO /2 or MINDO /3 method. For A –H…?B systems, the core resonance integrals are individually parametrized depending upon the class of the interaction. Three types of A—H…?B systems have been thus far parametrized. Nine hydrogen-bonded dimers have been studied using the new formalism and the current CNDO /2 and the MINDO /3 methods. MINDO /3 predicts very large interatomic (A –B) distances for the equilibrium geometry, and relatively small stabilization values for the hydrogen-bond energies. CNDO/2 predicts the reverse. The new formalism for both CNDO /2 and MINDO /3 predicts accurate geometries as well as energies for all nine dimers. The new formalisms are called CNDO /2H and MINDO /3H. A general discussion of the nature of hydrogen bonding as exhibited by CNDO /2H and MINDO /3H is presented. 相似文献
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The electronic structure of polyethylene has been calculated using crystal orbital theory and the latest version (MINDO/3) of the MINDO semi-empirical SCF MO method. The results are in better agreement with the observed photoelectron spectrum than those given by an analogous calculation using MINDO/2, which in turn has been shown superior to treatments based on EHT, CNDO, INDO, or ab initio SCF procedures. 相似文献
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Properties of the potential energy surface of protonated ethylene are calculated by semiempirical methods (CNDO/2-FK, MINDO/2, MINDO/3). These methods were chosen in respect of the agreement with new strong energy data concerning the relative stability of the nonclassical and a classical structure of the ethyl cations. They give no stationary point in that region of the hypersurfaces where until now was assumed to exist the most stable of the classical ethyl cations. The H-eclipsed classical cation is a saddle point on the CNDO/2-FK- and the MINDO/2-hypersurface, which represents the barrier of potential energy for the H-exchange in the ethyl cation; on the MINDO/3-surface a flat sea modified the character of the saddle point. Finally the results of the different quantum chemical methods (including NDDO and ab initio) are analysed concerning their agreement in calculating geometry and the distribution of electron density in the ethyl cations. 相似文献
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Non-empirical SCF calculations have been used to investigate the relative stabilities of the open and closed forms of ozone. In these studies several different sized basis sets have been employed, the best basis set being at about the level of a double-zeta set plus d-polarization functions. In contrast to the predictions of the CNDO/2, INDO and MINDO methods, the non-empirical SCF studies correctly predict that the open form of ozone is more stable. Thus these results show that the area of deficiency in the CNDO/2, INDO and MINDO results for this system is not in the SCF approximation. 相似文献