几种含芯电子相关能修正的G2和G2(ACI)方法

针对冻结芯电子近似，在MP2/6-311G(d,p)级别上对G2、MP2/6-311G(d)和MP2/6-311G(d,p)级别上对G2(QCI)方法进一步考虑了芯电子相关能修正，尝试建立了G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)方法。G2-l test set 的反应能量计算结果表明，这些方法进一步减小了经验修正量；G2(QCI/ful)和G2(QCI/fu2)也比G2(QCI)的总体精度有所提高；但G2(fu2)在G2基础上，总体精度没有改善。G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)计算G2-l test set反应能量的平均绝对偏差分别为5.11、4.74和4.81kJ mol-1,G2和G2(QCI)分别为5.09和4.97kJ mol-1.

Core Electronic Correlation Modifications to G2 and G2(QCI) Theories

In addition to our previous work of G2(ful) in Ref.8],we proposed a further core electronic correlation modifieation at MP2/6-31G(d) level to G2(QCI),namely G2(QCI/ful),and that at MP2/6-311G(d,p) level to G2 and G2(QCI) theories,namely G2(fu2) and G2(QCI/fu2).The latter would need no additional calculation if the geometry is optimized at MP2(full)/6-311G(d,p) level/The modification energies,ΔE(fu2),were calculated via eq. ΔE(ful)=EMP2](full)/6-31G(d)]-EMP2(FC)/6-31G(d)] ΔE(fu2)=EMP2](fu2)/6-311G(d,p)]-EMP2(FC)/6-311G(d,p)] G2 and G2(QCI) theories were modified via eq. EG2(fu2)]=E(G2)=ΔE(fu2)-HLC(G2)=HLCG2(fu2)] EG2(QCI/ful)]=EG2(QCI)]+ΔE(ful)-HLCG2(QCI)]+HLCG2(QCI/ful)] EG2(QCI/fu2)]=EG2(QCI)]+ΔE(fu2)-HLCG2(QCI)]+HLCG2(QCI/fu2)] where, HLCG2(fu2)]=-0.19nα-4.32nβ HLCG2(QCI/ful)]=-0.19nα-4.77nβ HLCG2(QCI/fu2)]=-0.19nα-4.65nβ It has been shown that the empirical High-Level-Correction(HLC) to either of the original G2 or G2(QCI) theory was reduced.G2(fu2) did not improve the over-all accuracy for the 125 G2-l test set reaction energies,however both G2(QCI/ful) and G2(QCI/fu2) did.The average absolute deviations (AAD) for the 125 reaction energse in the G2-l test set were reduced from 4.97 forG2(QCI) to 4.74 for G2(QCI/ful) and to 4.81kJ mol-1 for G2(QCI/fu2).The AAD was5.11 for G(fu2) compared with 5.09kJ mol-1 for G2.The reason for the larger AAD of G2(fu2) is probably due to that we did not use the better geometry of MP2(full)/6-311G(d,p) as presented in Ref.11],and the 6-311G basis sets was somewhat unsatisfactory to describe both of the first-an secone-row atoms as had been criticized in Ref.9].