I am trying to model the active sites of several MOF's using Gaussian 09 Unix package. One such MOF I have to model is MIL-100 and I am constantly finding difficulties in obtaining a converged structure due to its complex active site, which include three Ferric ions and an Oxide ion. I tried to start building up the active site with only three Ferric ions and the Oxide ion at first and then adding up the organic ligands but even the four atomic system failed to converge.
Is there any specific method I should proceed in obtaining the optimized active site? I tried using a small basis sets like 3-21G but the problem persists. I am using B3LYP method.
The active site of MIL-100 is attached herewith.
Please pay attention to the following points:
1. First of all, for optimizing a such big system, it is better to optimize the structure with a less accurate but simple method and basis set, then optimize the structure resulted from this geometry optimization using more accurate method and basis set.
2. Please try the LANL2DZ basis set for the iron (Fe)
3. You can increase the number of cycles using "maxcyc"
4. You can use "xqc"
Dear Ms Bamdad,
Thank you for the suggestions.
I started with a much simpler system of Ferric ion surrounded by three oxygen atoms using HF/3-21G, but it still did not converge. I have tried quadratic convergence as well, but still it did not.
Regards,
Dilhan
Did you try the LANL2DZ basis set for the iron? please use the LANL2DZ basis set for the iron and a basis set much bigger than the 3-21G such as 6-31+G(d) for other atoms. Maybe I can help you much better, If I could consider your input file.
- Badges
- Science topic