HX体系电子对内、对间相关研究

在6-311+G^*基组水平上用CISD（configurationinteractionwithsinglyanddoublyexcitedconfigurations)方法研究HX(X=Li-F,HBe)体系电子对内、对间的相关能。计算结果表明不同元素形成的HX(X=Li-F,HBe^+,HBe)体系,其价层电子对内、对间相关能的变化较大,它们之间存在着轨道差别,不宜将其相关贡献归为简单的常数。在使用相同理论方法和相同质量基组的前提下,电子数将直接影响到电子对间相关能的大小。对于多电子体系,电子对间相关在总相关中占有优势,若将其忽略会引起较大误差。     

Cl,Cl-和MCl(M=H,Li9 Na,K)对内对间相关能的规律性

通过对内对间相关能的计算,发现Cl, Cl-及其化合物中的K电子层的对内相关能基本上是一常数,而且Cl的K,L层电子层内相关能和它们之间的层间相关能也变化很小.另外,所研究的MCI系列化合物中Cl价电子对相关能的贡献是跟MCI的离子性有关,即随着化合物离子性的增加而增加,但其相关能最大不大于Cl-离子的,最小不小于Cl原子的.这些规律对人们考虑一些化合物的相关能,以至化学反应能量很有参考意义.     

Cl,Cl~-和MCl(M=H,Li,Na,K)对内对间相关能的规律性

通过对内对间相关能的计算,发现Ｃｌ,Ｃｌ－及其化合物中的Ｋ电子层的对内相关能基本上是一常数,而且Ｃｌ的Ｋ,Ｌ层电子层内相关能和它们之间的层间相关能也变化很小．另外,所研究的ＭＣｌ系列化合物中Ｃｌ价电子对相关能的贡献是跟ＭＣｌ的离子性有关,即随着化合物离子性的增加而增加,但其相关能最大不大于Ｃｌ离子的,最小不小于Ｃｌ原子的．这些规律对人们考虑一些化合物的相关能,以至化学反应能量很有参考意义．     

Cl,Cl-和MCl(M=H,Li,Na,K)对内对间相关能的规律性

通过对内对间相关能的计算,发现Cl,Cl^-及其化合物中的K电子层的对内相关能基本上是一常数,而且Cl的K,L层电子层内相关能和它们之间的层间相关能也变化很小.另外,所研究的MCl系列化合物中Cl价电子对相关能的贡献是跟MCl的离子性有关,即随着化合物离子性的增加而增加,但其相关能最大不大于Cl^-离子的,最小不小于Cl原子的.这些规律对人们考虑一些化合物的相关能,以至化学反应能量很有参考意义.     

多原子强离子键KX(X = OH, NC)及(KX)2体系电子相关能的简单计算

通过MELD程序MP2-OPT2方法在6-311++G(d)及6-311++G(3df, 3pd)基组下对KX(X = OH, NC)体系对内对间电子相关能的计算结果和分析, 并根据KX(X = OH, NC)分子中K和X组分的内层电子对相关能和内层电子相关效应的传递性, 定义并且计算了K^δ +和K^δ -对KX分子体系的电子相关能贡献. 基于K⁺, X-和KX(X = OH, NC)的对相关能的比较结果, 提出了利用其组成金属离子和负离子基团的电子相关能之和来计算多原子强离子键分子体系电子相关能的简单计算方法, 此方法对Gaussian98程序MP2(full)/6-311++G(d)水平下二聚体系(KOH))₂和(KNC))₂的电子相关能的近似计算结果误差很小, 应用此“化整为零”的方案计算大分子离子键体系电子相关能既可以基本达到化学计算要求的精度又能节约大量的计算工作量.     

HF,Ne等电子体系对内对间电子相关能的比较研究

采用MELD程序ROHF－OPT1方法在MP2/6-311++G(d)水平上,计算了HF分子基态1^∑和Ne原子基态1^S的对内对间电子相关能,并对两等电子体系的对相关能进行了分析和比较,深入研究两等电子体系对内对间相关能所具有的共同规律和存在的差异性,通过比较说明分子内的化学键是影响电子相关能的重要因素之一。HF分子和Ne原子两体系三重激发和四重激发对体系电子相关能的贡献的计算结果表明高激发项对电子相关能的贡献在精确量子化学计算中是不可以忽略的。     

HF,Ne等电子体系对内对间电子相关能的比较研究

采用MELD程序ROHF－OPT1方法在MP2/6-311++G(d)水平上,计算了HF分子基态1^∑和Ne原子基态1^S的对内对间电子相关能,并对两等电子体系的对相关能进行了分析和比较,深入研究两等电子体系对内对间相关能所具有的共同规律和存在的差异性,通过比较说明分子内的化学键是影响电子相关能的重要因素之一。HF分子和Ne原子两体系三重激发和四重激发对体系电子相关能的贡献的计算结果表明高激发项对电子相关能的贡献在精确量子化学计算中是不可以忽略的。     

从头算和ABEEMσπ/MM对(CH_3OH)_n(n=3～12)和[Na(CH_3OH)_n]~+(n=3～6)体系的研究

采用从头算方法(ab initio)和原子-键电负性均衡浮动电荷分子力场方法(ABEEMσπ/MM),对甲醇团簇(CH_3OH)n(n=3~12)和[Na(CH_3OH)_n]~+(n=3~6)体系的结构、电荷分布和结合能进行研究.依据从头算结果构建上述体系的ABEEMσπ/MM浮动电荷势能函数,并确定相关参数.结果表明,ABEEMσπ/MM所获得的结构和结合能等均优于OPLS/AA力场,并与从头算结果相符,其中键长的平均绝对偏差(AAD)小于0.004 nm,键长、键角和结合能的相对均方根偏差(RRMSD)分别小于3.8%,1.7%和6.8%;电荷分布与从头算结果的线性相关系数均大于0.99.     

C28H4-nCln(n=1~3)与CH4-nCln(n=1~3)的结构和电子光谱的理论研究

用INDO系列方法对C28H3Cl, C28H2Cl2, C28HCl3, CH3Cl, CH2Cl2, CHCl3进行了几何构型优化, C28H3Cl, C28HCl3, CH3Cl, CH3Cl为C3v对称性,C28H2Cl2, CH2Cl2为C2v对称性, 这六个分子的基态都是稳定闭壳层分子, 以此构型为基础计算了上述分子的电子光谱, C28H4-nCln(n=1~3)的电子光谱属于理论预测性质。     

立体效应和分子内诱导效应对R—X(R=烷基)键离解能变化趋势的影响

解释了"为什么R—X键离解能变化趋势不相同"的问题.R—X键离解能(BDE)可归因于3个主要因素:C—X固有健能,1,3成对排斥和分子内电荷-诱导偶极.当X原子给定,R—X(R=Me,Et,i-Pr,t-Bu)的BDE变化趋势由1,3成对排斥和分子内电荷-诱导偶极两个因素控制,前者减少R—X的BDE,后者增加或者减少R—X的BDE.在R—X为R—C键的系列化合物中(例如R—Me,R—CH==CH2,R—C≡≡CH,R—CN等),1,3成对排斥减少R—X的BDE,R—C键能变化趋势依R=Me,Et,i-Pr,t-Bu次序减小;对于X原子电负性小于C原子的R—X系列化合物(例如R—H,R—BH2,和R—SiH2等),上述两个因素均减小R—X的BDE,因而R—X键能变化趋势依R=Me,Et,i-Pr,t-Bu次序减小;对于X原子电负性大于C原子的R—X系列化合物(例如R—F,R—OH,R—Cl,R—Br,R—I,和R—NH2等),1,3成对排斥减少R—X的BDE,而分子内电荷-诱导偶极则增加R—X的BDE,于是R—X键能变化趋势取决于两者的竞争,结果表现为:(1)有的系列R—X键能变化依R=Me,Et,i-Pr,t-Bu次序增大(如R—F,R—OH等);(2)有的系列R—X键能变化依R=Me,Et,i-Pr,t-Bu次序减小(如R—I);(3)有的系列R—X键能变化依R=Me,Et,i-Pr,t-Bu次序变化很小(如R—Br).     

Changing Rules of Bonding Electron Pair Correlation Energies of CH3X （X = F, OH, NH2） Systems

1 INTRODUCTION It has been known that the electron correlation energy of molecular systems was, and still is, one of the most serious bottleneck problems to the chemis- try accuracy of computational quantum chemistry. Since L鰓din[1] gave the definition …     

Rules on intrapair and interpair correlation energy for Cl, Cl~(-) and MCI (M=H, Li, Na, K)

According to the calculation results of the intrapair and interpair correlation energy for the title systems, it has been found that the intrapair correlation energy of K shell of Cl is almost a constant and both the intrashell and intershell correlation energy of K and L shell changes little. It has also been found that in MCI series compounds the value of Cl correlation energy contribution depends on the ionicity of MCI compounds, i.e., the Cl correlation energy contribution increases with the increase of the ionic bond strength of the compound and this value is always less than the correlation energy of Cl" anion but always larger than that of Cl atom. These rules are helpful for the estimation of the correlation energy of ionic compounds and the energy changes of chemical reactions.     

Study on Pair Correlation Energies of Isoelectronic Systems F~-,HF and H_2F~+

IntroductionAsawell knownfact ,thecalculationofelectroncor relationenergyisabottleneckprobleminthecalculationsofmolecularpropertiesandchemicalreactionsinquantumchemistry .1Ithasattractedgreatattentionoftheoreticalchemists.NumerousdifferentmethodshavebeenusedtocalculatethecorrelationenergysinceL wdin2 givethedef initionofelectroncorrelationin 195 9.In 196 0s ,Sinanoˇglu3,4 definedtheexactelectronpaircorrelationen ergyanddevelopedmany electrontheoryofatomsandmoleculesinwhichthetotalcorrelation…     

Rules of electron correlation energies of van der Waals' complexes RgX (Rg = Ar,Kr, X = F,Cl, Br)

First, the intrapair and interpair correlation energies of the Rg atom, X atom, and the optimized RgX (Rg = Ar, Kr, X = F, Cl, Br) complexes are calculated by the MELD program at the 6‐311++g(d), 6‐311++g(3df, 3pd), and cc‐pvqz basis sets (denoted by basis sets a, b, and c, respectively). It is found that the relationship E_corr(RgX) ≈ E_corr(Rg) + E_corr(X) is correct for all the above systems but introducing an unsound absolute error for some RgX systems. Second, the same calculations are selectively carried out for ArF (the smallest system) and KrBr (the largest system) at their increasing interatomic distance. It was found that both the correlation energies of ArF and those of KrBr will decrease whenever the interatomic distance of them become larger. On the basis of our results, we provided an approach to quickly estimate the correlation energies of RgX complexes by which not only the absolute error becomes smaller but more computation work is saved than the direct calculation. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Simple estimation of electron correlation energy for multi-atomic strong ionic compounds KX and (KX)2 (X=OH, NC)

On the basis of the calculations and analyses of the intrapair and interpair correlation energy of KX (X = OH, NC) molecules and the results of the transferability of both the innermost intrapair correlation energy and the inner core effect of K and X in KX molecules, we defined and calculated the K^δ+ and X^δ-correlation contributions to the total correlation energy of KX molecules. With the comparison of the pair correlation energy of K⁺, X^- and KX systems, we present a simple estimation method to estimate the electron correlation energy of strong ionic compound by summarizing the correlation energy of its constituent ion and ionic group. By using this simple method, the reasonable estimation results of the correlation energy of (KOH)₂ and (KNC)₂ have been obtained at mp2/6-311++G(d) level with Gaussian98 program, and the deviations are very small. Applying the scheme of “Separate Large System into Smaller Ones” to the calculation of electron correlation energy of large ionic compounds, it can not only save lot of computation work but also reach the chemical accuracy.     

Study on Pair Correlation Energies of Isoelectronic Systems F^－, HF and H2F^＋

The intrapair and interpair correlation energies of F-, HF and H2F^ systems are calculated and analyzed using MP2-OPT2 method of MELD program with cc-PVSZ^* basis set. From the analysis of pair correlation energies of these isoelectronlc sysoterns, it is found that the 1sF^2 pair correlation energy is trans-ferable in these three isociectronic systems. According to the definition of pair correlation contribution of one electron pair to a system, the pair correlation contribution values of these three systems are calculated. The correlation contribution values of inner electron pairs and H—F bonding electron pair in HF molecule with those in H2F^ system are compared. The results indicate that the bonding effect of a molecule is one of the im-portant factors to influence electron correlation energy of the system. The comparison of correlation energy contributions in-cluding triple and quadruple excitations with those only includ-ing singles and doubles calculated with 6-311 G(d) basis set shows that the higher.excitation correlation energy contribution gives more than 2 % of the total correlation energy for these sys-tems.     

Atomic Partitioning of the MPn (n = 2, 3, 4) Dynamic Electron Correlation Energy by the Interacting Quantum Atoms Method: A Fast and Accurate Electrostatic Potential Integral Approach

Recently, the quantum topological energy partitioning method called interacting quantum atoms (IQA) has been extended to MPn (n = 2, 3, 4) wave functions. This enables the extraction of chemical insight related to dynamic electron correlation. The large computational expense of the IQA-MPn approach is compensated by the advantages that IQA offers compared to older nontopological energy decomposition schemes. This expense is problematic in the construction of a machine learning training set to create kriging models for topological atoms. However, the algorithm presented here markedly accelerates the calculation of atomically partitioned electron correlation energies. Then again, the algorithm cannot calculate pairwise interatomic energies because it applies analytical integrals over whole space (rather than over atomic volumes). However, these pairwise energies are not needed in the quantum topological force field FFLUX, which only uses the energy of an atom interacting with all remaining atoms of the system that it is part of. Thus, it is now feasible to generate accurate and sizeable training sets at MPn level of theory. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.     

Simple estimation of electron correlation energy for multi-atomic strong ionic compounds KX and (KX)2 (X = OH, NC)

On the basis of the calculations and analyses of the intrapair and interpair correlation energy of KX (X = OH, NC) molecules and the results of the transferability of both the innermost intrapair correlation energy and the inner core effect of K and X in KX molecules, we defined and calculated the Kδ- and Xδ-correlation contributions to the total correlation energy of KX molecules. With the comparison of the pair correlation energy of K+, X- and KX systems, we present a simple estimation method to estimate the electron correlation energy of strong ionic compound by summarizing the correlation energy of its constituent ion and ionic group. By using this simple method, the reasonable estimation results of the correlation energy of (KOH)2 and (KNC)2 have been obtained at mp2/6-311++G(d) level with Gaussian98 program, and the deviations are very small. Applying the scheme of "Separate Large System into Smaller Ones" to the calculation of electron correlation energy of large ionic compounds, it can not only     

Structure and properties of the aluminum borates Al(BO2)n and Al(BO2)n(-), (n = 1-4)

The geometrical and electronic structures of Al(BO(2))(n) and Al(BO(2))(n)(-) (n = 1-4) clusters are computed at different levels of theory including density functional theory (DFT), hybrid DFT, double-hybrid DFT, and second-order perturbation theory. All aluminum borates are found to be quite stable toward the BO(2) and BO(2)(-) loss in the neutral and anion series, respectively. Al(BO(2))(4) belongs to the class of hyperhalogens composed of smaller superhalogens, and should possess a large adiabatic electron affinity (EA(ad)) larger than that of its superhalogen building block BO(2). Indeed, the aluminum tetraborate possesses the EA(ad) of 5.6 eV, which, however, is smaller than the EA(ad) of 7.8 eV of the AlF(4) supehalogen despite BO(2) is more electronegative than F. The EA(ad) decrease in Al(BO(2))(4) is due to the higher thermodynamic stability of Al(BO(2))(4) compared to that of AlF(4). Because of its high EA and thermodynamic stability, Al(BO(2))(4) should be capable of forming salts with electropositive counter ions. We optimized KAl(BO(2))(4) as corresponding to a unit cell of a hypothetical KAl(BO(2))(4) salt and found that specific energy and energy density of such a salt are competitive with those of trinitrotoluol (TNT).     

(CoMn)n(n=1～5)合金团簇的结构和磁性

All geometry structures of (CoMn)n (n=1-5) clusters were optimized, and the energy, frequence and magnetism of (CoMn)n (n=1-5) clusters were calculated by using the local spin density approximation and generalized gradient approximation of density functional theory. The same ground state structures of CoMn alloy clusters were confirmed in two methods, and magnetism of CoMn alloy ground state clusters was studied systemically. In order to understand structure and magnetism of CoMn alloy clusters better, Co2n (n=1-5) and Mn2n (n=1-5) clusters were calculated by the same method as alloy clusters, whose ground state structure and magnetism were confirmed. Moreover, the ground state structure and magnetism of clusters with the corresponding CoMn alloy clusters was compared. Results indicated that for (CoMn)n (n=1-4) clusters, geometry structures of CoMn alloy clusters are the same as the corresponding pure clusters still, (CoMn)3 and (CoMn)4 exhibit magnetic bistability, show ferromagnetic and anti-ferromagnetic coupling, local magnetic moment of Co, Mn atoms in CoMn alloy clusters almost preserves magnetism of pure clusters still.