Ab initio and DFT benchmark study for nucleophilic substitution at carbon (SN2@C) and Silicon (SN2@Si)
Ab initio and DFT benchmark study for nucleophilic substitution at carbon (SN2@C) and Silicon (SN2@Si)
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DOI：
10.1002/jcc.20261
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发表时间：
2005-11-15
影响因子：
3
通讯作者：
Bickelhaupt, FM
中科院分区：
文献类型：
--
作者：
Bento, AP;Solà, M;Bickelhaupt, FM
为了获得氯阴离子在氯甲烷中的碳（S(N)2@C）和氯硅烷中的硅（S(N)2@Si）两个原型亲核取代反应的一组一致的基准势能面（PES），我们使用了一系列从头算方法[HF， MP2, MP4SDQ， CCSD， CCSD(T)]，并结合六种高斯型基集的层次化系列，直到g极化。作为基集大小的函数，驻在点的相对能量收敛到0.01 ~ 0.56 kcal/mol。在CCSD(T)CCSD(T)/aug-cc-pVQZ下，[Cl-， CH3Cl]络合物的过渡态[Cl- ch3 -Cl]（-）和稳定的[Cl- sih3 -Cl]（-）过渡态的相对能量分别为-10.42,+2.52和-27.10 kcal/mol。此外，我们还研究了四种常见的密度泛函，即BP86， BLYP， B3LYP和OLYP，结合一个大的双极化slater型三ζ质量基集（TZ2P）在这些反应中的性能。OLYP和B3LYP与我们的CCSD(T)/aug-cc-pVQZ基准的总体一致性最好。OLYP对S(N)2@C总垒和中心垒表现较好，分别低估了2.65和4.05 kcal/mol。其他DFT方法低估了这些势垒，约4.8 （B3LYP）至9.0 kcal/mol （BLYP）。(c) 2005 Wiley期刊有限公司
To obtain a set of consistent benchmark potential energy surfaces (PES) for the two archetypal nucleophilic substitution reactions of the chloride anion at carbon in chloromethane (S(N)2@C) and at silicon in chlorosilane (S(N)2@Si), we have explored these PESes using a hierarchical series of ab initio methods [HF, MP2, MP4SDQ, CCSD, CCSD(T)] in combination with a hierarchical series of six Gaussian-type basis sets, up to g polarization. Relative energies of stationary points are converged to within 0.01 to 0.56 kcal/mol as a function of the basis-set size. Our best estimate, at CCSD(T)CCSD(T)/aug-cc-pVQZ, for the relative energies of the [Cl-, CH3Cl] reactant complex, the [Cl-CH3-Cl](-) transition state and the stable [Cl-SiH3-Cl](-) transition complex is -10.42, +2.52, and -27.10 kcal/mol, respectively. Furthermore, we have investigated the performance for these reactions of four popular density functionals, namely, BP86, BLYP, B3LYP, and OLYP, in combination with a large doubly polarized Slater-type basis set of triple-zeta quality (TZ2P). Best overall agreement with our CCSD(T)/aug-cc-pVQZ benchmark is obtained with OLYP and B3LYP. However, OLYP performs better for the S(N)2@C overall and central barriers, which it underestimates by 2.65 and 4.05 kcal/mol, respectively. The other DFT approaches underestimate these barriers by some 4.8 (B3LYP) to 9.0 kcal/mol (BLYP). (c) 2005 Wiley Periodicals, Inc.