含能材料中键离解能的密度泛函理论计算

通过计算一个包括臭氧,硝基甲烷以及1,3,5 -三硝基-1,3,5-三氮杂环已烷(RDX)在内的典型系统的键离解能,对由四种交换/相关函数(BLYP,B3LYP,B3PW91和B3P86)加上不同的基函数组合而成的多种密度泛函方法的准确性进行了比较研究.结果表明:B3P86/6-31G**是计算该系统C-NO2,O-O和N-NO2键离解能的最可靠的方法.     

碱金属双原子分子部分电子态的完全振动能谱和离解能

对大多数双原子分子电子态的高阶振动能谱,现代实验方法和量子力学理论计算都难以得到较精确的振动能级.文中应用基于二阶微扰理论的代数方法(AM)以及计算双原子分子离解能的新表达式研究了碱金属双原子分子Li₂的3³Σ⁺_g,1³Δ_g和2³Π_g,Na₂的B¹Π_u以及K₂的4¹Σ⁺_g电子态的完全振动能谱{E_υ^AM}和离解能,理论计算结果不仅与已有的实验值相符,而且还给出了实验尚未得到的高阶振动能级.这些结果为碱金属双原子分子精确振动能谱和离解能的科学研究提供了重要数据. 关键词： 碱金属分子 高阶振动能级 离解能 代数方法     

LiF中空位形成能的第一性原理计算

采用平面波展开和基于密度泛函理论框架下的第一性原理赝势法,计算了102GPa下LiF化合物中Li空位和F空位的形成能及空间周围的原子弛豫,讨论了空位形成时电荷密度的重新分布,相应的电子态密度以及能带结构等性质.结果表明:LiF晶体中F空位的形成能比大于Li空位的形成能;F空位对LiF晶体的电子结构等性质的影响要比Li空位的大.     

LiF中空位形成能的第一性原理计算

采用平面波展开和基于密度泛函理论框架下的第一性原理赝势法,计算了102GPa下LiF化合物中Li空位和F空位的形成能及空间周围的原子弛豫,讨论了空位形成时电荷密度的重新分布,相应的电子态密度以及能带结构等性质.结果表明:LiF晶体中F空位的形成能比大于Li空位的形成能;F空位对LiF晶体的电子结构等性质的影响要比Li空位的大.     

On one-electron basis set extrapolation of atomic and molecular correlation energies

It is well known that the convergence of correlation energies in atomic and molecular calculations is relatively slow and that calculations aimed at high accuracy must explicitly make corrections for this. In this work we consider 1e ^? basis set extrapolation as a means of obtaining high accuracy. The correlation consistent basis sets of Dunning et al. have provided a convenient platform for extrapolation, with the independent variable being X?=?D,?T,?Q,?5,?…?. There has been much debate in the literature about the functional form to use for the extrapolation, with contention between the ‘theoretically justified’ (X?+?1)^?3 form and empirical forms based on exponentials or variable powers. We will dissect the theoretical justification of the (X?+?1)^?3 form by considering MP2 calculations on He and Ne as a function of the maximum angular momentum (?) in the basis using basis sets having converged radial extent. Calculations with ? up to 14 were carried out for Ne. It is shown that while the asymptotic form of (??+?1)^?3 is clearly reached, higher order terms are very important in the range of ? normally used in molecular calculations. We also use similar analysis techniques for an open shell atom and a small molecule. The functional form for the dependence of molecular properties with ? is complex and it is safer to extrapolate fitting parameters than energies.     

Substituent effects on the formation of sulfonyl cations from sulfonyl chlorides: comparisons of solvolysis kinetic data with calculated gas phase energies

Suitable theoretical methods are validated for organosulfur compounds using experimental data for gas phase enthalpies of formation, proton affinities (PA) and heterolytic bond dissociation enthalpies (HBDEs). From enthalpies of chloride anion transfers from neutral chlorides to acyl, sulfonyl or cumyl cations in the gas phase, it is calculated that (i) similar aromatic substituent effects are expected for heterolyses of acyl, sulfonyl and cumyl chlorides; (ii) HBDEs for loss of chloride increase by over 70 kcal mol^?1 from 4‐MeOC₆H₄COCl to SO₂Cl₂. Rate constants for solvolyses of 4‐Z‐substituted arenesulfonyl chlorides (Z = OMe, Me, H, Cl, NO₂) in 97% w/w 2,2,2‐trifluoroethanol (TFE)–water are reported. Substituent effects are smaller than observed for identical solvolyses of acyl and cumyl chlorides, and are much smaller than those predicted theoretically for gas phase unimolecular heterolysis (explained by variable amounts of nucleophilic solvent assistance). Copyright © 2007 John Wiley & Sons, Ltd.     

Size effects on cation heats of formation. IV. Methyl and ethyl substitutions in methyl,methylene, acetylene and ethene

An empirical relation between the heat of formation of molecular ions and cation size is used to study the effects of methyl and ethyl substitution of hydrogen atoms on the cations of the C_nH_m hydrocarbons methyl, methylene, acetylene and ethene. The results provide tests of the graphical method, revealing regularities and irregularities in the empirical size relation used, as well as its value as a predictive tool for determining cation and neutral heats of formation. Of the 36 C_nH_m cations studied, only 5 have heats of formation listed in the renowned ATcT tables. Some C_nH_m cation heats of formation are questioned or eliminated, mainly in cases where multiple choices are available in the literature. Proposals are made for investigating or re-investigating the ionisation energies and the heats of formation of several of the molecules studied where no data previously exist or where our analysis suggests that more reliable values are needed. The relative effects of methyl and ethyl substitution on the thermodynamic stability of the series of alkyl-substituted C_nH_m cations are discussed.     

三硝基甲烷键离解能和生成焓的理论计算

采用密度泛函(DFT)四种交换/相关函数(B3LYP、B3P86、B3PW91和PBE0)结合不同的基函数,求得了三硝基甲烷C-NO2键的离解能(BDE),并且通过合理选择参考物硝基甲烷,设计等键等电子对反应,计算了气相三硝基甲烷分子的生成焓(HOF).与实验数据进行比较,PBE0/6-31g*计算出的BDE值最好,误差为-2.1 kcal mol-1;PBE0密度泛函结合带极化函数的6-31g基组得到的HOF值与实验值吻合的最好(误差在0.1 kcal mol-1以内).     

Geometrical structures,vibrational frequencies,force constants and dissociation energies of isotopic water molecules （H2O,HDO, D2O,HTO, DTO,and T2O） under dipole electric field

The dissociation limits of isotopic water molecules are derived for the ground state. The equilibrium geometries, the vibrational frequencies, the force constants and the dissociation energies for the ground states of all isotopic water molecules under the dipole electric fields from -0.05 a.u. to 0.05 a.u. are calculated using B3P86/6-311++G(3df,3pf). The results show that when the dipole electric fields change from -0.05 a.u. to 0.05 a.u., the bond length of H-O increases whereas the bond angle of H-O-H decreases because of the charge transfer induced by the applied dipole electric field. The vibrational frequencies and the force constants of isotopic water molecules change under the influence of the strong external torque. The dissociation energies increase when the dipole electric fields change from -0.05 a.u. to 0.05 a.u. and the increased dissociation energies are in the order of H2O, HDO, HTO, D2O, DTO, and T2O under the same external electric fields.     

多硝基苯酸酯炸药分子键离解能与撞击感度关系研究

用密度泛函方法,在B3LYP-6-31G*、B3P86/6-31G*和B3LYP-6-311G*三种理论水平对四个含硝基烷基的苯酸酯炸药分子进行了几何结构全优化、能量和频率计算。并对这些炸药分子苯环上的C-NO2和烷基上的C-NO2键离解能分别进行了三种理论水平的计算。结果表明,这类分子中的最弱键是烷基上的C-NO2键。进一步分析实验撞击感度与分子中最弱键离解能量的关系,结果表明,分子最弱键离解能与分子总能量的比值BDE/E和实验撞击感度h50%之间存在一个几乎线性的关联关系。BDE/E是表征炸药撞击感度的一个实用的合理指针。     

NaK分子的完全振动能谱和离解能的研究

使用作者建立的基于微扰理论的代数方法(AM),研究了碱金属异核双原子NaK的 、 两个电子态的振动光谱常数和振动能谱;使用基于AM的代数能量方法（AEM）研究了这些电子态的离解能。结果表明：根据少数精确的实验振动能级[ ],用AM方法获得了精确的分子振动光谱常数集合,还首次获得了包含所有高振动量子态能级的正确的完全振动能谱{ };用AEM方法获得的分子离解能比由文献发表的振动光谱常数计算得到的离解能值更准确。     

NaK分子的完全振动能谱和离解能的研究

使用作者建立的基于微扰理论的代数方法(AM),研究了碱金属异核双原子NaK的 、 两个电子态的振动光谱常数和振动能谱;使用基于AM的代数能量方法（AEM）研究了这些电子态的离解能。结果表明：根据少数精确的实验振动能级[ ],用AM方法获得了精确的分子振动光谱常数集合,还首次获得了包含所有高振动量子态能级的正确的完全振动能谱{ };用AEM方法获得的分子离解能比由文献发表的振动光谱常数计算得到的离解能值更准确。     

NaLi分子的完全振动能谱和离解能的研究

文章使用作者建立的基于微扰理论的代数方法(AM),首次研究了碱金属异核双原子分子NaLi的 、 、 三个电子态的振动光谱常数和振动能谱;使用基于AM的代数能量方法（AEM）研究了这些电子态的离解能。结果表明：根据少数精确的实验振动能级[ ],用AM方法获得了精确的分子振动光谱常数集合,还首次获得了包含所有高振动量子态能级的正确的完全振动能谱{ };用AEM方法获得的分子离解能比由文献发表的振动光谱常数计算得到的离解能值更准确。     

Accurate studies on the full vibrational energy spectra and molecular dissociation energies for some electronic states of halogen molecule

This paper obtains accurate vibrational spectroscopic constants and full vibrational energy spectrum by the algebraic method (AM) for some electronic states of halogen diatomic molecules.Motivated by the recent success of obtaining the dissociation energies of Li 2 molecule by using a new analytical formula,it further extends the formula to study the dissociation energies of halogen diatomic molecules.The results show that the AM spectrum and the theoretical dissociation energies agree well with RKR data and experimental data respectively.     

分子部分电子态的高阶振动能级和离解能的精确研究

鉴于K₂分子电子态的振动能谱和分子离解能D_e在实际研究和应用中的重要性,应用Sun,Ren等人提出的基于微扰理论的代数方法(AM)和基于AM的代数能量方法(AEM)研究了K₂分子的X¹Σ⁺_g,a³Σ⁺_u,0^-_g,B¹Π_{u< 关键词： 2}分子')" href="#">K₂分子 代数方法 高阶振动能级 离解能     

部分气体双原子分子的完全振动能谱和离解能的精确研究

鉴于气体双原子分子H2、O2、N2和CO的高振动激发态能级和离解行为在实际研究中的重要性,本文应用代数方法(AM)和代数能量方法(AEM),以部分气体双原子分子有限的实验能级[Ev]为基础,获得了H2-X1∑ g、O2-A3∑ u、O2-c1∑-u、N2-X1∑ g和CO-X1∑ 共5个电子态的完全振动能谱{Ev}及其分子的离解能,为研究部分离解气体的物理和化学性质提供了重要的高振动激发态能级和可靠的离解能数据.     

碱金属氢化物双原子分子部分电子态的完全振动能谱和分子离解能的精确研究

应用作者建立的基于微扰理论能级表达式的代数方法，研究了碱金属氢化物双原子分子⁶LiH，⁷LiH，NaH，KH，RbH和CsH的A¹Σ⁺电子态的完全振动能谱{E_υ}，并应用基于代数方法的代数能量方法分别研究了以上各分子电子态的离解能.得到了这些电子态的精确的振动光谱常数和包括接近分子离解极限在内的完全振动能谱以及正确的理论离解能，从而为许多需要这些双原子分子的精确振动光谱的科学研究提供了必要的数据. 关键词： 碱金属氢化物 代数方法 振动能级 离解能     

Accurate studies on the full vibrational energy spectra and molecular dissociation energies for some electronic states of N_2 molecule

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…     

双原子离子振动光谱与离解能的研究

结合代数方法(AM)和最近建立的计算精确的分子离解能的新解析表达式,进一步研究了部分双原子离子电子态的完全振动能谱和离解能,获得了与实验值符合得非常好的理论结果.研究结果表明,AM方法和新解析式相结合的理论方法同样也适用于双原子离子体系,该方法在理论上提供了获得双原子离子精确的振动光谱和离解能的物理新方法.     

Thermodynamic test of defect formation energies calculated by simulation techniques for nonstoichiometric oxides. application to CeO2−x, UO2 ± x, TiO2−x, Mn1−xO,Fe1−xO

A relation has been derived between (i) ΔH(O₂), the partial molar enthalpy of mixing of oxygen in a nonstoichiometric oxide, which may be directly measured by high temperature microcalorimetry, and (ii) the defect formation energies which may be calculated by simulation techniques. This relation permits the testing of the consistency between the experimental ΔH(O₂) and the theoretical defect formation energies. This thermodynamic test, though necessary, is not sufficient since it does not take entropy terms into account. As yet this test can be rigorously applied only for small deviations from stoichiometry, but may be however very useful for large deviations. Applications have been developed for the oxides UO_2+x, UO_2?x, TiO_2?x, Mn_1?xO, Fe_1?xO and CeO_2?x. For the first five oxides, it concluded that the theoretical formation energies for the majority defects derived from simulation calculations are not compatible with experimental ΔH(O₂). A good agreement is found for CeO_2?x.