Chemical Shift Calculations with Charge Embedding

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jdhart84
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Chemical Shift Calculations with Charge Embedding

Post by jdhart84 » 12 Jan 2015, 22:46

I am attempting to calculate the chemical shifts of small molecules embedded in an array of point charges and as of yet have not had luck in determining the correct way to proceed. Using the polaziable embedding model implemented in Dalton2013 I have run a series of test calculations only including charge terms in the embedding to compare against equivalent calculations in Gaussian 09. The SCF energies compare nicely, however there is rather severe disagreement between the calculated isotropic shifts. Looking through the documentation I have noticed that is has not been explicitly stated that charge embedding should work with NMR calculations at the DFT level, yet I have not received any error messages when I attempt to do so with basic calculations. I would greatly appreciate any guidance the community could provide in this regard. Thank you.

arnfinn
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Re: Chemical Shift Calculations with Charge Embedding

Post by arnfinn » 12 Jan 2015, 23:11

Can you provide us with a Dalton output example?

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magnus
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Re: Chemical Shift Calculations with Charge Embedding

Post by magnus » 13 Jan 2015, 08:22

The polarizable embedding code in Dalton2013 does not support London atomic orbitals which is probably why the shifts do not agree. It is an unfortunate oversight that no error printed. LAOs will be supported in the next release. You can use the older QMMM code instead. It requires a different potential input file but if you are only using charges this shouldn't be too difficult.

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