I want to conduct an adsorption study. The systems are contained with about maximum of 129 atoms and almost 600+ electrons.. Most of these sytems are contained with non-metals.
Is using B3LYP-D3(BJ)/6-31G(d,p) good? Or should I use M06-2X/6-31G(d,p) ? Though I wanted to use B3LYP-D3(BJ)...
Hello,
That's a low level of theory, but its a big molecule, so there is a balance. I think they key is benchmarking a little bit (calculating known similar smaller molecules and comparing the results vs. experiment/X-ray etc) to get comfortable. Try all of those approaches on something small that has a known value that you can compare with (like X-ray structure, reaction energy, etc.). Also, what kind of atoms? If there are metals, that level of theory won't be the best for metals. You could do ONIOM where you do a higher level of theory for non C,H,O,N and use that level for C,H,O,N.
Kyle
I wanted to use a larger basis but due to these big systems it will be little harder. i have another question, is B3LYP-D3(BJ) is good functional when considering non-metallic systems??
I think it should be fine, but do a little benchmarking on smaller systems with known values of what you are after (structure? delta G of reactions?). What kind of info do you want from the calcs?
I want to conduct a study on drug delivery of several anti-cancer drugs on several nanostructures. For that some parameters like Geometry, adsorption energy, thermodynamic and some electronic parameters are needed. And I've considered wB97XD and B3LYP-D3 functional with 6-31G(d,p) basis set in Gaussian 9 suite. Can you please tell me which functional will give me greater accuracy? And if these methods are good enough(both wB97XD and B3LYP-D3)??
I read some previous benchmark study some of them says B3LYP is not that good even with D3 correction, some says good.
I am getting confused...
(All systems are consist of non-metal atom except boron which is metalloid)
Hi Palash,
Yeah it's a confusing mess out there. That said, you want to be confident that your values are good and be able to back up the method you used with citations. If there is a paper benchmarking the approaches for similar nanostructures and drugs, you can refer to that to back up your approach. Check this paper out and see if you are comfortable with the mean errors with your approach. Article Performance of B3LYP Density Functional Methods for a Large ...
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