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Isotopes

Posted: Thu Nov 05, 2020 4:14 am
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.

Re: Isotopes

Posted: Sat Nov 07, 2020 6:30 pm
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.