wB97XD算NICS报错No C6 coefficient available for IA= 0的解决方法

sobereva

算NMR时报错No C6 coefficient available for IA=  XXX是因为当前色散校正对XXX元素没有定义参数所致
在计算NICS时，需要设置Bq原子指定计算的位置，这时候如果用了色散校正，就会报错No C6 coefficient available for IA=  0（这个问题至少在G16 B.01及以前都有，C.01没试过）。对于用DFT-D3的情况，只要不写empiricaldispersion关键词就可以避免。而对于wB97XD、B97D之类自带色散校正的泛函，遇到这种错误时，解决办法是加上IOp(3/124=4)，这要求强制不使用色散校正。此时算出的能量结果就等于wB97XD里去了DFT-D2校正部分，而NMR、NICS数据都是严格意义的wB97XD级别的。
PS：wB97X和wB97XD不是只相差色散校正的关系，其它参数也有不同，因此这俩泛函算的NMR/NICS是不同的。

Aminus

C6 Coefficients and Dipole Polarizabilities for All Atoms and Many Ions in Rows 1–6 of the Periodic Table
https://doi.org/10.1021/acs.jctc.6b00361

Using time-dependent density functional theory (TDDFT) with exchange kernels, we calculate and test imaginary frequency-dependent dipole polarizabilities for all atoms and many ions in rows 1–6 of the periodic table. These are then integrated over frequency to produce C6 coefficients. Results are presented under different models: straight TDDFT calculations using two different kernels; “benchmark” TDDFT calculations corrected by more accurate quantum chemical and experimental data; and “benchmark” TDDFT with frozen orbital anions. Parametrizations are presented for 411+ atoms and ions, allowing results to be easily used by other researchers. A curious relationship, C6,XY ∝ [αX(0)αY(0)]0.73, is found between C6 coefficients and static polarizabilities α(0). The relationship C6,XY = 2C6,XC6,Y/[(αX/αY)C6,Y + (αY/αX)C6,X] is tested and found to work well (<5% errors) in ～80% of the cases, but can break down badly (>30% errors) in a small fraction of cases.

sobereva

Aminus 发表于 2023-6-16 01:09
C6 Coefficients and Dipole Polarizabilities for All Atoms and Many Ions in Rows 1–6 of the Period ...

跟当前帖子没关系
Bq没有C6系数而报错是计算程序考虑不周的问题，不是物理上的问题