Department of Chemistry, Washington State University, Pullman, Washington 99164, USA.
J Chem Phys. 2010 Feb 7;132(5):054108. doi: 10.1063/1.3308483.
Correlation consistent basis sets have been optimized for accurately describing core-core and core-valence correlation effects with explicitly correlated F12 methods. The new sets, denoted cc-pCVnZ-F12 (n=D, T, Q) and aug-cc-pC(F12)VnZ (n=D, T, Q, 5), were developed by augmenting the cc-pVnZ-F12 and aug-cc-pVnZ families of basis sets with additional functions whose exponents were optimized based on the difference between all-electron and valence-electron correlation energies. The number of augmented functions added is fewer, in general, than in the standard cc-pCVnZ and cc-pwCVnZ families of basis sets. Optimal values of the geminal Slater exponent for use with these basis sets in MP2-F12 calculations are presented and are also recommended for CCSD-F12b calculations. Auxiliary basis sets for use in the resolution of the identity approximation in explicitly correlated calculations have also been optimized and matched to the new cc-pCVnZ-F12 series of orbital basis sets. The cc-pCVnZ-F12 basis sets, along with the new auxiliary sets, were benchmarked in CCSD(T)-F12b calculations of spectroscopic properties on a series of homo- and heteronuclear first and second row diatomic molecules. Comparing the effects of correlating the outer core electrons in these molecules with those from conventional CCSD(T) at the complete basis set limit, which involved calculations with new cc-pCV6Z basis sets for the second row elements that were also developed in the course of this work, it is observed that the F12 values are reasonably well converged already at just the triple-zeta level.
已经为准确描述核心-核心和核心价电子相关效应优化了相关一致基集，以使用显式相关 F12 方法。新的基集表示为 cc-pCVnZ-F12（n=D、T、Q）和 aug-cc-pC（F12）VnZ（n=D、T、Q、5），是通过在 cc-pVnZ-F12 和 aug-cc-pVnZ 基集系列中添加额外的函数来开发的，这些函数的指数是根据全电子和价电子相关能之间的差异优化的。添加的扩展函数的数量通常比标准的 cc-pCVnZ 和 cc-pwCVnZ 基集系列少。在 MP2-F12 计算中使用这些基集的最佳 geminal Slater 指数值也已提出，并建议用于 CCSD-F12b 计算。还优化了用于显式相关计算中身份解析近似的辅助基集，并与新的 cc-pCVnZ-F12 轨道基集系列匹配。cc-pCVnZ-F12 基集以及新的辅助集在一系列同核和异核第一和第二行双原子分子的 CCSD(T)-F12b 计算中进行了基准测试，用于计算光谱性质。比较这些分子中外核电子相关的影响与完全基集限制下的常规 CCSD(T)的影响，这涉及到使用新开发的第二行元素的 cc-pCV6Z 基集的计算，这也是在这项工作的过程中开发的，观察到 F12 值在仅仅三重-zeta 水平上已经相当收敛了。
