wzkchem5 发表于 2024-5-22 18:40
确定这个反应在CCSD(T)级别下不是无垒反应吗？
sunwukong 发表于 2024-5-22 15:08
用DFT算有能垒，大概有1 kj/mol，怎么看ccsd(t)下是不是无垒反应？
wzkchem5 发表于 2024-5-22 22:28
用CCSD(T)做柔性扫描，如果扫描的键长范围足够宽，且扫描曲线光滑，能量单调变化，就说明没有过渡态
sunwukong 发表于 2024-5-22 15:33
好的，谢谢大佬。另外想问下，用VDZ和VTZ会影响molpro能不能算出来吗？
sunwukong 发表于 2024-5-22 22:33
好的，谢谢大佬。另外想问下，用VDZ和VTZ会影响molpro能不能算出来吗？
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.
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).
mizu-bai 发表于 2024-5-24 08:48
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-pVDd ...
mizu-bai 发表于 2024-5-24 08:48
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-pVDd ...
wjc404 发表于 2024-6-8 16:01
刚用DSD-PBEP86-D3/def2-TZVP算了一下，在C-O距离2.3埃处可以找到一个中间体，其结构如下：
C -0.11 ...
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