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.     

卤化氢HX（X=F,Cl,Br,I）与C2H2相互作用本质的量子化学研究

在MP2水平上,采用全电子基组,对C2H2与HX(X=F,Cl,Br,I)相互作用进行了研究.构型优化同时进行频率验证,得到4个T型结构的稳定复合物,相互作用能在-12.761～-7.086kJ/mol之间.自然键轨道(NBO)与分子中的原子(AIM)理论分析表明,形成复合物分子间的电荷转移量都很少,最大仅为0.009a.u.,作用强度与氢键类似.对称性匹配微拢理论(SAPT)能量分解数据表明,对于C2H2…HX(X=F,Cl,Br,I)体系,从F到I,静电作用逐渐减弱,色散作用逐渐增强;相互作用能中对吸引能的贡献主要为静电能和色散能,二者之和占到80%以上,诱导能所占的比例很小,卤化氢与乙炔分子间相互作用的本质为静电作用和色散作用.     

NHn(n=1～3)体系电子对内对间相关能的变化规律

众所周知,电子相关能问题是量子化学的瓶颈问题‘’‘．为了更深人地了解和认识电子相关能的轨道本质,建立P。St－HF理论校正模型,JS等”－”应用电子对内对间电子相关模式,指出国际著名量子     

基态XO~（n＋）（X=Ru,Rh,Pd;n=0,1）的势能函数和第一垂直电离势

运用原子分子反应静力学原理推导出XOn+(X=Ru,Rh,Pd;n=0,1)的基态电子状态及离解极限.运用密度泛函的B3P86方法和LANL2DZ赝势基组及aug-cc-pVTZ全电子基组,对XOn+X=Ru,Rh,Pd;n=0,1)体系进行计算,获得了这些分子及其离子基态的Murrell-Sorbie解析势能函数.同时计算了XOn+(X=Ru,Rh,Pd;n=0,1)的光谱数据,计算了XO(X=Ru,Rh,Pd)中性分子的第一垂直电离势.     

基态XOn+(X=Ru,Rh, Pd|n=0, 1)的势能函数和第一垂直电离势

运用原子分子反应静力学原理推导出XOn+(X=Ru, Rh, Pd; n=0, 1)的基态电子状态及离解极限. 运用密度泛函的B3P86方法和LANL2DZ 赝势基组及aug-cc-pVTZ全电子基组, 对XOn+(X=Ru, Rh, Pd; n=0, 1)体系进行计算, 获得了这些分子及其离子基态的Murrell-Sorbie解析势能函数. 同时计算了XOn+(X=Ru, Rh, Pd; n=0, 1)的光谱数据, 计算了XO(X=Ru, Rh, Pd)中性分子的第一垂直电离势.     

价键结构函数与键函数 2.水分子的计算和分析

应用键表酉群方法对水分子进行了计算分析, 并用键函数定量讨论了成键电子对之间.成键电子对与孤电子对之间及孤电子对间的相互作用,计算表明H~2O中氧原子与两个HIs成键的两个杂化轨道密度重心偏离O-H联线,氧原子实际上以两个P轨道与HIs成键.     

价键结构函数与键函数 2.水分子的计算和分析

应用键表酉群方法对水分子进行了计算分析, 并用键函数定量讨论了成键电子对之间.成键电子对与孤电子对之间及孤电子对间的相互作用,计算表明H~2O中氧原子与两个HIs成键的两个杂化轨道密度重心偏离O-H联线,氧原子实际上以两个P轨道与HIs成键.     

DNA甲基化-非甲基化碱基间堆积作用的理论研究

运用二级Mфller-Plesset(MP2)理论方法和cc-pVDZ基组优化了6-甲基鸟嘌呤(O6-MethylG),4-甲基胸腺嘧啶(O4-MethylT)以及5-甲基胞嘧啶(C5-MethylC)与DNA碱基鸟嘌呤(G),腺嘌呤(A),胞嘧啶(C),胸腺嘧啶(T)之间的堆积构型.在MP2/aug-cc-pVXZ//MP2/cc-pVDZ(X=D,T)水平上,采用完全基组外推方法校正了堆积碱基对间的相互作用能,并用完全均衡校正法(CP)校正了基组重叠误差(BSSE).MP2计算结果表明,DNA碱基甲基化使得嘧啶-嘧啶、嘧啶-嘌呤堆积碱基间的平行旋转角发生明显改变,并使堆积碱基间的相互作用能增大.在MP2/cc-pVDZ计算级别上得到了各堆积碱基对的全电子波函数,并用分子中的原子理论(AIM)分析了堆积碱基对间的弱相互作用.AIM分析结果显示,甲基化增强了堆积碱基间的π-π作用,且甲基氢与相邻碱基间形成H2CH…X(X=O,N,CH3,NH2)等类型的氢键.甲基化损伤使碱基间重叠程度增大、π-π作用增强以及堆积碱基间形成多个氢键,是堆积作用能增加的主要原因.     

大体系分区密度泛函计算方法

提出一种新的对大体系进行分区密度泛函计算的方法。将大体系划分为若干较小的区,每个小区是一个相对独立的量子力学子体系,计及其它区势场的影响和电子的Pauli排斥作用,可以进行相对独立的密度泛函计算。对各子体系求解单电子方程：(F^k F^kp)C^k=S^kC^kε^k K=A,B,C,…式中F^k,C^k,S^k,ε^k分别为子体系K的Fbck矩阵、轨道系数矩阵、基组重叠矩阵和本征值矩阵,F^kb起强制属于不同子体系的占据轨道之间保持正交的作用。得到的轨道是分区定域化的,汇总各区的计算结果得出整个体系的电子结构信息。通过对一些较大分子的计算,考察了几种因素对分区计算精度的影响。结果表明,提出的方法是可行的,通过控制各区基组的大小,可以基本消除基组截断误差,得到精确的计算结果。对于足够大的体系,本方法是一种线性标度算法;和文献报道的相关方法比较,更容易用于对体系的某些区域进行特别的计算研究。     

价层电子对互斥理论的改进——计算中心原子价层电子对数的新方法

对氢、卤素、氧族元素作配位原子时提供的价电子数做了合理的解释，并推导出计算中心原子价层电子对数的新方法，该方法不需要书写路易斯结构式再确定成键电子对数和孤电子对数，也不必规定不同族的原子作配位原子时提供的价电子数，只需要根据公式即可直接得到中心原子的价层电子对数。     

On electron correlation in NaCl2

This article reports the intrapair and interpair electron correlation energies of the radical NaCl₂. The total interpair correlation energy dominates. Hence, the interpair electron correlation energy must be considered in building models for correcting computed correlation energies. The 6-311+G* basis set recovers only 32% of the total estimated correlation energy and 44% of this amount came from the core electrons. © 1995 John Wiley & Sons, 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     

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.     

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。     

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.     

Rules on pair electron correlation in MOH (M=H,Li, Na)

In this article, the transferable property of pair correlation energies of OH components is discussed for a series of OH containing compounds MOH (M=H, Li, Na). In this series of compounds, from OH free radicals through HOH, LiOH, NaOH to OH^?, both the intra‐ and interpair correlation energies and intra‐ and intershell correlation energies of the inner orbital electrons change little. The 1s$_{\mathrm{O}}^{2}$ is very much alike in all the above OH containing systems and such a pair correlation is transferable. But the interpair correlation and intrashell correlation energies of the valence electrons are large and change a lot in all systems. In MOH molecules, the OH correlation energy contribution increases with the increase of the ionic bond strength of the compound and this contribution is always between the correlation energy values of OH free radicals and OH^? atomic groups. For strong ionic compounds, we present a very simple method to estimate the correlation energy by adding the correlation energies of its component ions within the chemical accuracy (2 kcal/mol). © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 311–317, 2001     

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.     

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.