What kind of energy does vef.pl output?

Vasp transition state theory tools

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DrChenXray
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Joined: Mon Sep 26, 2016 10:24 pm

What kind of energy does vef.pl output?

Post by DrChenXray »

I'm trying to do some benchmarking based on adsorption enthalpy. I have adsorption enthalpy values obtained from experiments. I have also simulated initial and final state of a simple molecular adsorption. However, I'm not sure what kind of energy vef.pl outputs. What kind of energy does vef.pl output?
Also, what kind of corrections are needed to convert the energy difference of initial and final state of adsorption obtained from vef.pl to an experimentally obtained adsorption enthalpy?

Many thanks.
graeme
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Re: What kind of energy does vef.pl output?

Post by graeme »

It outputs what vasp calculates: the internal energy of the system. This does not include PV or TS terms.

To compare with experiment you need to calculate some energy difference between a state of interest and a reference state. Then, depending upon the experimental measurement, you may need to correct for PV to get enthalpy or also TS to get free energy. There could also be nuclear quantum effects, such as zero point and tunneling.
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