A general method in considering the core electromc correlation energies has been proposed and introduced into the standard Gaussian-2 (G2)[7] theory hy small post-Hartree-Fock calculations. In this papcr an additional...A general method in considering the core electromc correlation energies has been proposed and introduced into the standard Gaussian-2 (G2)[7] theory hy small post-Hartree-Fock calculations. In this papcr an additional MP2(FC)/6-31G(d) calculation over the G2 procedures is employed and examined in modihcation in modification to the flaw of Frozen-Core (FC) approximation of G2 vai eq:E(full)= E[MP2(full)/6-31G(d)]-E[MP2(FC)/6-31G(d)]where the MP2(full)/6-31G(d) cnergy has been obtaincd in the molefular gcometry optimizations. This energy, E(full), is directly added into the total G2 energy of a molecule in facilitating the effect of core electronic correlations for each molecule in chemical reactions. It has been shown that the over-all avcrage absolute deviation for the 125 reaction energies of the G2 test set (test set 1) is slightly reduced from 5.09 to 5.01 kJ, mol(-1) while for the 55 D0 values, which have been used for the derivation of the A coefficient of the empirical High-Level-Correction (HLC), it is also reduced from 4.99 [for both G2 and G2(COMPLETE)[8]]to 4.77 kJ, mol(-1). In addition, Iargcr crrors (greater than ±8.4 kJ. mol(-1) for the D0 energies are improved, especially for the largest error of the D0of SO2 This error is reduced from 21.3 to 15.4 kJ. mol(-1), in which the experimental geometry would further reduce it by 7.1kJ.mol(-1)[8].Another improvement is the absolute value of the A coefficient in HLC being reduced from 4.81 for G2 to 4.34 milli-hartrees which is believed to be useful in isolating the relationship between the HLC and the FC approximation.Modifications to the original G2 from this work is denoted as G2(fu 1) and thus the G2 (fu 1) total energy for a molecule isE[G2(fu 1)]= E[G2]+ E(full)with a new E[HLC] =0.19α- 4.34nβ milli-hartree.展开更多
在HF和CCSD水平上研究了重金属团簇Ag2X(X=Se,Te,Po)中电子相关效应.结果显示,电子相关效应改变键角大于16°,但几乎不改变键长,说明电子相关效应是作用在重金属原子上的一种切向吸引力.理论分析确定,这个吸引力来自于重金属闭壳层d...在HF和CCSD水平上研究了重金属团簇Ag2X(X=Se,Te,Po)中电子相关效应.结果显示,电子相关效应改变键角大于16°,但几乎不改变键长,说明电子相关效应是作用在重金属原子上的一种切向吸引力.理论分析确定,这个吸引力来自于重金属闭壳层d10-d10之间的van der Waals吸引力.采用一个较简单的经典模型拟合了电子相关势能函数,并估算了它的大小和作用模式.展开更多
文摘A general method in considering the core electromc correlation energies has been proposed and introduced into the standard Gaussian-2 (G2)[7] theory hy small post-Hartree-Fock calculations. In this papcr an additional MP2(FC)/6-31G(d) calculation over the G2 procedures is employed and examined in modihcation in modification to the flaw of Frozen-Core (FC) approximation of G2 vai eq:E(full)= E[MP2(full)/6-31G(d)]-E[MP2(FC)/6-31G(d)]where the MP2(full)/6-31G(d) cnergy has been obtaincd in the molefular gcometry optimizations. This energy, E(full), is directly added into the total G2 energy of a molecule in facilitating the effect of core electronic correlations for each molecule in chemical reactions. It has been shown that the over-all avcrage absolute deviation for the 125 reaction energies of the G2 test set (test set 1) is slightly reduced from 5.09 to 5.01 kJ, mol(-1) while for the 55 D0 values, which have been used for the derivation of the A coefficient of the empirical High-Level-Correction (HLC), it is also reduced from 4.99 [for both G2 and G2(COMPLETE)[8]]to 4.77 kJ, mol(-1). In addition, Iargcr crrors (greater than ±8.4 kJ. mol(-1) for the D0 energies are improved, especially for the largest error of the D0of SO2 This error is reduced from 21.3 to 15.4 kJ. mol(-1), in which the experimental geometry would further reduce it by 7.1kJ.mol(-1)[8].Another improvement is the absolute value of the A coefficient in HLC being reduced from 4.81 for G2 to 4.34 milli-hartrees which is believed to be useful in isolating the relationship between the HLC and the FC approximation.Modifications to the original G2 from this work is denoted as G2(fu 1) and thus the G2 (fu 1) total energy for a molecule isE[G2(fu 1)]= E[G2]+ E(full)with a new E[HLC] =0.19α- 4.34nβ milli-hartree.
文摘在HF和CCSD水平上研究了重金属团簇Ag2X(X=Se,Te,Po)中电子相关效应.结果显示,电子相关效应改变键角大于16°,但几乎不改变键长,说明电子相关效应是作用在重金属原子上的一种切向吸引力.理论分析确定,这个吸引力来自于重金属闭壳层d10-d10之间的van der Waals吸引力.采用一个较简单的经典模型拟合了电子相关势能函数,并估算了它的大小和作用模式.
