Isotopes

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loening
Posts: 3
Joined: Fri Aug 07, 2020 1:27 am
Full Name: Nikolaus Loening
Organization: Lewis & Clark College
Subdiscipline: Chemistry

Isotopes

Post by loening »

Is there a way to change isotopes in WebMO? In particular, it would be great if it was possible to use deuterium atoms instead of hydrogens, as that makes a substantial difference in the calculation of vibrational frequencies and kinetic isotope effects. I imagine this could be added as an adjustable parameter the way that charge is handled.

jwk
Posts: 12
Joined: Sat Jun 20, 2020 3:37 am
Full Name: John Keller
Organization: University of Alaska Fairbanks
Subdiscipline: Chemistry

Re: Isotopes

Post by jwk »

Different isotopes do not affect the electronic energy; they only change the vibrational frequencies, and therefore affect the zero point energy, enthapy and free energy. Isotope information must be entered manually in the input file of the QM package (click View, Generate in WebMO to see the input file which you can edit). For example, in Gaussian, you use freq=readisotopes. Check the gaussian.com/keywords web page for more details.

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