自由基聚合反应物相对分子质量分布的计算

结合隐函数和ＭｏｎｔｅＣａｒｌｏ方法，给出了自由基聚会反应物相对分子质量分布函数的可计算解的形式。分析积分函数的性质，确定了有效积分区间，提高了计算速度，给出苯乙烯本体聚合反应物相对分子质量分布的理论计算结果，与实验结论一致。     

三元合金生成热的一种计算方法

本文将半经验模型计算二元合金生成熟的方法，推广至三元合金，计算了Ｌａ－Ｆｅ－Ａｌ，Ｆｅ－Ａｌ，Ｆｅ－Ｎｉ－Ｖ，Ｃｕ－Ｐｄ－Ｓｉ等三元合金体系生成热，并与实验结果比较，符合很好，这种计算方法可预测三元合金生成热及固溶区的范围，并可最终产物存在的可能性。     

密度泛函理论下的分子电负性（IV）——大环分子的总能量和电…

以密度泛函理论表述的电负性定义其均衡原理为基础，提出了一个修正电负性均衡方法（ＭＥＥＭ），可直接用于计算各类分子的总能量和原子电荷分布，通过对３个较大环状分子１８－ｃｒｏｗｎ－６，２４－ｃｒｏｗｎ－８和２４－ｃｒｙｐｔａｎｄ的实际计算，发现其计算结果与从头计算结果接近。     

活性白土的制备

活性白土的制备谭钦德，陈淑荷，谭志诚（佛山大学化学系佛山５２８０００）关键词膨润土，活性白土，活化工艺活化是膨润土深加工中的一个基本工艺过程。活性白土既可直接用作医药、化妆品和涂料等的原料，也可用于油品制造的脱色以及碱性、极性基团的吸附工艺［１～３］...     

分子力场进展

分子力学（简称ＭＭ）是近年来化学家常用的一种计算方法。与量子力学从头计算和半经验方法相比，用分子力学处理大分子可以大大节省计算时间，而且，在大多数情况下，用分子力学方法计算得到的分子几何构型参数与实验值之间的差值可在实验误差范围之内。所以，分子力学是研究生物化学体系的有效和可行的手段。分子力学的核心是分子力场。本文介绍了分子力场的量子力学背景、分子力场和光谱力场之间的关系。分子力场的一般形式、分力     

计算化学键离子性的新经验公式

自从Pauling提出键的离子性概念和键离子性的定量标度以来，人们从不同角度相继提出了好几个计算化学键离子性百分率的方法。1932年，Pauling认为化学键的离子性百分率可由下式计算：     

烷烃Wiener指数的简便计算法

本文总结了烷烃Ｗｉｅｎｅｒ指数的计算方法，提出了一个计算支链烷烃系列Ｗｉｅｎｅｒ指数的简便方法，并给出了３３个支链烷烃系列Ｗｉｅｎｅｒ指数的计算公式。应用这些公式，可由碳原子数直接算得支链烷烃的Ｗｉｅｎｅｒ指数。     

N-取代螺旋共轭化合物非线性光学性质的理论研究

以量子化学半经验AM1方法优化几何构型为基础，采用FF／AMl和INDO-SOS方法计算了N-取代螺旋共轭化合物的非线性光学系数，讨论了N原子不同取代位置对螺旋共轭体系结构、电子光谱、非线性光学系数的影响．计算结果表明，N杂原子的引入可改善体系的非线性光学性质，所设计的分子具有较大的二阶非线性光学系数和较好的透明性．     

原子-键电负性均衡方法参数的确定与探讨

原子-键电负性均衡方法(ABEEM)是以密度泛函理论(DFT)和电负性均衡原理为基础发展而来，它明确地考虑了化学键是不引入任何实验数据的带纯理论性和计算的方法．使用统一标准并具有代表性和全面性地选择了200多个模型分子，利用可得到较准确结构的MP2／6-31G*优化结构，心／STO-3G单点计算得到Mulliken重叠布居，再用最小二乘法拟合得到许多主族元素在分子体系中的诸原子(包括单、双和叁键等不同成键状态)和化学键的ABEEM参数．所得到的原子的价态电负性可与已提出的其他电负性标度相比拟，计算CO得到的电荷负端为C(与从头计算的结果相反)，结果与实验相符，且原子电荷的正负不完全由原子电负性决定．     

孪函数N电子基组的组态

分析了各类孪函数Ｎ电子基组态展开式的特点以及它们对体系相关能的贡献，提出了一种在享函数Ｎ电子基矢下进行多组态自洽场计算时的组态选取方法，并依此方法在ＳＴＯ－６－３１Ｇ基组下对ＬｉＨ分子的基态能量做了计算，结果表明，用该组态选取方法只需选取少量的组态波函数便可得到相当精确的计算结果。     

无需标准溶液的酸碱滴定计算分析研究

无需标准溶液的滴定计算分析能同时求出滴定剂与被测物质浓度.本文用非线性规划问题的单纯形加速法对无需标准溶液的酸碱滴定进行了研究.单元酸、多元酸及混合酸的测定得到了比较满意的结果.     

Using many-particle basis sets for electronic energy calculations of molecules

A method of calculating the electronic energies of molecules using a many-particle basis set is proposed. In this case, the many-particle Schrödinger equation may be solved without resorting to the one-electron approximation. The results of the electronic energy calculations of some two-electron systems are in good agreement with experimental results.     

A method and program for accurate determination of Kováts' retention indices with special reference to multicomponent mixtures

Summary A method for calculating accurate Kováts' retention indices, without the need for bracketing every compound in a mixture by two consecutive n-alkanes, is described. In addition, the method makes possible good control of the column conditions. The calculation is done using a FORTRAN program which is adapted to automatic operation and which also takes into consideration the change of retention time with the amount of substance injected.     

A method for calculating the Gibbs energy of nonspecific solvation

A method for calculating the Gibbs energy of nonspecific solvation of nonelectrolytes was suggested. The new equation for the Gibbs energy of nonspecific solvation contains one solvent parameter that characterize nonspecific solvent-solute interactions and two experimental Gibbs energies of solvation in two standard solvents. The method is applicable to a wide range of solutes and solvents. It was successfully used to describe some 800 Gibbs energies of solvation for systems without specific solvent-solute interactions.     

Using inverted indices for accelerating LINGO calculations

The ever growing size of chemical databases calls for the development of novel methods for representing and comparing molecules. One such method called LINGO is based on fragmenting the SMILES string representation of molecules. Comparison of molecules can then be performed by calculating the Tanimoto coefficient, which is called LINGOsim when used on LINGO multisets. This paper introduces a verbose representation for storing LINGO multisets, which makes it possible to transform them into sparse fingerprints such that fingerprint data structures and algorithms can be used to accelerate queries. The previous best method for rapidly calculating the LINGOsim similarity matrix required specialized hardware to yield a significant speedup over existing methods. By representing LINGO multisets in the verbose representation and using inverted indices, it is possible to calculate LINGOsim similarity matrices roughly 2.6 times faster than existing methods without relying on specialized hardware.     

Modified scheme for calculation of atomization enthalpies of molecules within the framework of the MINDO/3 method

Conclusions A modified scheme was proposed for calculating the atomization emthalpies of molecules within the framework of the MINDO/3 method without optimization of the geometric parameters.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2399–2401, October, 1982.The authors thank V. I. Faustov for supplying the program used to make the calculations by the MINDO/3 method.     

Quantitative analysis of cannabinoids from Cannabis sativa using 1H-NMR

A (1)H-NMR method has been developed for the quantitative analysis of pure cannabinoids and for cannabinoids present in Cannabis sativa plant material without any chromatographic purification. The experiment was performed by the analysis of singlets in the range of delta 4.0-7.0 in the (1)H-NMR spectrum, in which distinguishable signals of each cannabinoid are shown. Quantitation was performed by calculating the relative ratio of the peak area of selected proton signals of the target compounds to the known amount of the internal standard, anthracene. For this method no reference compounds are needed. It allows rapid and simple quantitation of cannabinoids with a final analysis time of only 5 min without the need for a pre-purification step.     

Including anharmonicity in the calculation of rate constants. 1. The HCN/HNC isomerization reaction

A method for calculating anharmonic vibrational energy levels in asymmetric top and linear systems that is based on second-order perturbation theory in curvilinear coordinates is extended to the bound generalized normal modes at nonstationary points along a reaction path. Explicit formulas for the anharmonicity coefficients, x(ij), and the constant term, E0, are presented, and the necessary modifications for resonance cases are considered. The method is combined with variational transition state theory with semiclassical multidimensional tunneling approximations to calculate thermal rate constants for the HCN/HNC isomerization reaction. Although the results for this system are not very sensitive to the choice of coordinates, we find that the inclusion of anharmonicity leads to a substantial improvement in the vibrational energy levels. We also present detailed comparisons of rate constants computed with and without anharmonicity, with various approximations for incorporating tunneling along the reaction path, and with a more practical approach to calculating the vibrational partition functions needed for larger systems.     

Assessing the efficiency of free energy calculation methods

The efficiencies of two recently developed methods for calculating free energy changes along a generalized coordinate in a system are discussed in the context of other, related approaches. One method is based on Jarzynski's identity [Phys. Rev. Lett. 78, 2690 (1997)]. The second method relies on thermodynamic integration of the average force and is called the adaptive biasing force method [Darve and Pohorille, J. Chem. Phys. 115, 9169 (2001)]. Both methods are designed such that the system evolves along the chosen coordinate(s) without experiencing free energy barriers and they require calculating the instantaneous, unconstrained force acting on this coordinate using the formula derived by Darve and Pohorille. Efficiencies are analyzed by comparing analytical estimates of statistical errors and by considering two numerical examples-internal rotation of hydrated 1,2-dichloroethane and transfer of fluoromethane across a water-hexane interface. The efficiencies of both methods are approximately equal in the first but not in the second case. During transfer of fluoromethane the system is easily driven away from equilibrium and, therefore, the performance of the method based on Jarzynski's identity is poor.