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
Enthalpy changes of the reactions involved in our previous papers have been re-examined at the G2(MP2) and G2 levels. The G2(MP2) and G2 energies of Ar, Ar+,ArAr+, ArCl+, ArF+, ArH+, ArHe+, ArNe+, ArO+, ArS+, H2+, He,...Enthalpy changes of the reactions involved in our previous papers have been re-examined at the G2(MP2) and G2 levels. The G2(MP2) and G2 energies of Ar, Ar+,ArAr+, ArCl+, ArF+, ArH+, ArHe+, ArNe+, ArO+, ArS+, H2+, He, HeCl+, HeF+, HeO+,HeS+, Ne, NeCl+, NeF+, NeO+ and NeS+ have been calculated. The G2(MP2) and G2 results for all of the interested reactions have also been compared with those of the previous MP2/6-31G** and MP4/6-311G (2df, 2pd) calculations. All of the G2(MP2) and G2 reaction enthalpies are improved from the MP2 and MP4 level of calculations when compared with the experimental data for the four categories of reactions as (1) iso-electronic, isogyric; (2) valence isoelectronic, isogyric; (3) isogyric and (4)non-isogyric reactions with the average absolute deviations of 5.10, 4.60, 7.70 and 9.20 for G2(MP2) and 4.18, 5.19, 6.78 and 6.49kJ·mol-1 for G2, respectively. The individural deviation for almost all of the reactions involved in this work is not more than±13kJ·mol-1 for G2(MP2) and ±8.4kJ·mol-1 for G2. In this paper, an additional number of reactions examined at the G2(MP2) and G2 levels as well as at the MP2/6-31G** and MP4/6-311G (2df, 2pd) levels of calculations have also been reported. The MP2, MP4, G2(MP2) and G2 total energies for the interested chemical species have been calculated if these energies have not been reported in literatures. All of the reaction energies at different levels have been compared with the experimental data in a nummber of reactions devided into the above four categories. The average absolute deviations are 25.9, 36.0, 29.2 and 40.1 for MP2; 8.41, 18.3, 17.2 and 18.3 for MP4; 9.41, 5.98, 4.85 and 6.90 for G2(MP2) and 6.69, 4.06, 3.85 and 4.60 kJ·mol-1 for G2, respectively. It is clear that the MP2 calculation did quite poor for all of the foux categories of reactions and the MP4 did well only for the isoelectronic and isogyric reactions. The G2(MP2) and G2 reproduce the eaperimental reaction enthalpy changes very well for all reactions in the four categories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Enthalpy changes of the reactions involved in our previous papers have been re-examined at the G2(MP2) and G2 levels. The G2(MP2) and G2 energies of Ar, Ar+,ArAr+, ArCl+, ArF+, ArH+, ArHe+, ArNe+, ArO+, ArS+, H2+, He, HeCl+, HeF+, HeO+,HeS+, Ne, NeCl+, NeF+, NeO+ and NeS+ have been calculated. The G2(MP2) and G2 results for all of the interested reactions have also been compared with those of the previous MP2/6-31G** and MP4/6-311G (2df, 2pd) calculations. All of the G2(MP2) and G2 reaction enthalpies are improved from the MP2 and MP4 level of calculations when compared with the experimental data for the four categories of reactions as (1) iso-electronic, isogyric; (2) valence isoelectronic, isogyric; (3) isogyric and (4)non-isogyric reactions with the average absolute deviations of 5.10, 4.60, 7.70 and 9.20 for G2(MP2) and 4.18, 5.19, 6.78 and 6.49kJ·mol-1 for G2, respectively. The individural deviation for almost all of the reactions involved in this work is not more than±13kJ·mol-1 for G2(MP2) and ±8.4kJ·mol-1 for G2. In this paper, an additional number of reactions examined at the G2(MP2) and G2 levels as well as at the MP2/6-31G** and MP4/6-311G (2df, 2pd) levels of calculations have also been reported. The MP2, MP4, G2(MP2) and G2 total energies for the interested chemical species have been calculated if these energies have not been reported in literatures. All of the reaction energies at different levels have been compared with the experimental data in a nummber of reactions devided into the above four categories. The average absolute deviations are 25.9, 36.0, 29.2 and 40.1 for MP2; 8.41, 18.3, 17.2 and 18.3 for MP4; 9.41, 5.98, 4.85 and 6.90 for G2(MP2) and 6.69, 4.06, 3.85 and 4.60 kJ·mol-1 for G2, respectively. It is clear that the MP2 calculation did quite poor for all of the foux categories of reactions and the MP4 did well only for the isoelectronic and isogyric reactions. The G2(MP2) and G2 reproduce the eaperimental reaction enthalpy changes very well for all reactions in the four categories
