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 ...

这是ts-aa过渡态，IRC是NO3*从一侧C到另一侧C的一个反应，不是关键的。
我用revDSD-PBEP86-D3(BJ)/mg3s算出来了上面ts-ra那个结构，DSD-PBEP86-D3/def2-TZVP 双杂化泛函水平的精度是介于DFT和CCSD(T)之间吗？

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     -0.115968   -0.078776   -0.022715
  C      1.230754   -0.026686   -0.172112
  H     -0.684667    0.805853    0.235124
  H     -0.651979   -1.009277   -0.154953
  H      1.772949    0.900861   -0.037498
  H      1.794184   -0.914727   -0.426212
  O      0.305143    0.399550   -2.226347
  N      0.265503   -0.723592   -2.971828
  O      0.366066   -1.803157   -2.424770
  O      0.127296   -0.500402   -4.154941

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 ...

大佬，CCSD(T)-F12a/aVDZ有点算不动，大概需要一个星期才能开始optg。
如果在CCSD(T)-F12a/VDZ下optg不下去，那改成aVDZ优化结果会改变吗？根据您的经验有差别很大的例子吗？
听sob老师说，优化对基组不是很敏感，可以先用小基组。

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 ...

题目错误纠正了。
我试试大佬提供的方法基组

如果要使用 Gaussian-MOKIT-Molpro 的话，最好先检测一些成键方式比较奇怪的结构的 ROHF 波函数稳定性，有时候 Gaussian 的 ROHF 得到的解可能有问题。

http://bbs.keinsci.com/forum.php ... 8&fromuid=37027

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？

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。

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？

有可能，但“能找到过渡态”和“计算结果靠谱”之间没有任何必然联系。你在给定级别下找到了过渡态的体系，实际既可能有过渡态，又可能没有过渡态；你在给定级别下没找到过渡态的体系，实际还是既可能有过渡态，又可能没有过渡态。只能说理论级别越高，计算结果（也就是反应是否存在过渡态）和实际相符的概率越大。

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

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 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？

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

确定这个反应在CCSD(T)级别下不是无垒反应吗？