|
|
你在标题中说用了 CCSD(T)/cc-pVDZ 优化，文中提到是 CCSD(T)-F12b/cc-pVDZ 和 CCSD(T)-F12b/jun-cc-pVDdZ，带不带 F12 是两种方法。CCSD(T)-F12 不能乱搭配基组：
In MOLPRO the F12 integrals can only be computed using density fitting (DF) approximations. The many electron integrals are approximated by resolutions of the identity (RI) expansions. Thus, F12 calculations require three different basis sets: the orbital (AO) basis, the DF basis, and the RI basis.
We recommend as AO basis sets the augmented correlation consistent basis sets (denoted AVnZ) or the specially optimized correlation consistent F12 basis sets (denoted VnZ-F12, cf. K.A. Peterson and H.-J. Werner, J. Chem. Phys. 128, 084102 (2008)). Normally, triples zeta basis sets (AVTZ or VTZ-F12) yield excellent results that are close to the basis set limit. Diffuse basis functions are rather essential both for the HF and MP2-F12 energies, and therefore the standard VTZ sets are not recommended. If the AVnZ, [A]VnZ-F12, or VnZ-PP-F12 orbital basis sets are used, suitable density fitting (DF) basis and resolution of the identity (RI) basis sets are automatically chosen. For the AVnZ orbital basis sets, AVnZ/MP2FIT and VnZ/JKFIT basis sets are used by default for the DF and RI, respectively. The associated optimized CABS basis set of Peterson et al. can be chosen by specifying RI_BASIS=OPTRI. For the [a]VnZ-F12 and [a][c]VnZ-PP-F12 orbital basis, the associated CABS (OPTRI) basis sets are used by default. However, OPTRI sets are not yet available for all elements, and in such cases an alternative RI basis must be explicitly specified using the RI_BASIS option.
https://www.molpro.net/manual/do ... _methods#basis_sets
另外 F12a 与 F12b 对基组的要求是不一样的：
It should be noted that these methods involve approximations and do not yield the exact CCSD-F12 energies. Preliminary experience has shown that the CCSD-F12A method slightly overestimates the correlation energies, while CCSD-F12B underestimates them. For AVDZ or AVTZ basis sets, CCSD-F12A usually gives very good results, but for larger basis sets it may overestimate the basis set limit and converge from below to the limit. Thus, convergence may not be monotonic, and extrapolation of the correlation energies should not be attempted. CCSD-F12B usually converges monotonically from below to the limit and gives best results for AVQZ and larger basis sets. Thus, we currently recommend CCSD-F12A for AVDZ and AVTZ basis sets, and CCSD-F12B for larger basis sets (rarely needed).
按我们课题组的经验，这个体系可能会用 UCCSD(T)-F12a/aug-cc-pVDZ 级别。 |
|
发表于 Post on 2024-5-22 17:45:13
|
只看该作者 Only view this author
|只看大图 View big picture
|倒序浏览 Reverse view
|阅读模式 Reading model
收藏 Add to favorites
楼主 Author