Hi all,
Typically, restricted to electron structure of organic molecules and Molecular Dynamics, I've only just started to look into transition metal complexes. My question, to accurately model an organic molecule with a single transition metal ion (zinc, copper, iron, cobalt) is a straight forward DFT electron structure optimisation (with the appropriate basis set) an accurate representation?
Should I be using DFT+U?
Does Gaussian support DFT+U (simple google searching isn't proving helpful)?
Is the U value for a particular transition metal a universal constant or will it depend on the environment? And if so, how to calculate it?
Lots of new material for me!
Thanks
Anthony
Hi Anthony,
to answer your first question: yes, from my experience, 'straightforward' DFT (like PBE, PW91, B3LYP, PBE1PBE etc.) could be used successfully as an accurate representation of organic complexes containing a single transition metal ion. B3LYP, for instance, was claimed to provide quite accurate spin-state ordering (although some people would disagree with that ;-) ). You can find lots of information about Gaussian DFT methods here:
http://gaussian.com/g_tech/g_ur/k_dft.htm
Hope it helps a little.
Best regards,
Aleksey.
Hi Aleksey, thanks for your answer. I work by myself on proteins in an office surrounded by people working on the electron structure of radioactive materials . I never seem to get a simple answer off them ;-) Thank again.
Hello Anthony,
As Aleksey says I suggest you to use the B3PW91. This functional is prepared properly and, in difference of B3LYP, can explain the homogeneous electron gas that it is necessary for metals. In general, B3PW91 is much better than B3LYP in a lot of cases.
On the other hand, DFT+U is specific for metals and should improve the result of spin-state of the metal more than any hybrid functional. But that depends of proprieties that you want to calculate, i.e, if you want to study some reactivity I think that hybrid will be the best option, specific metal proprieties DFT+U... I add to you a link that can have interesting information.
https://www.researchgate.net/post/Which_functional_LDA_GGA_HF_HF-LDA_sX_PBE_RPBE_PW91_WC_should_I_use_in_Castep_Calculation_to_simulate_silicon_energy
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