How to calculate gibbs free energy

[Ahmed Zenhom]

Hi I'm trying to calculate gibbs free energy between two transition states. I know the formula but I don't know how to get the parameters using nwchem (zero-point energy, electronic energy, etc....) any idea how to calculate it?

[Mario Schleep]

Hi,

It sound like you only did a geometry optimization. So you have to add the tasks you need. For your needs

task dft energy

task dft freq

should be fine (replace dft with what you want to do).

Here is the link to the documentation: https://nwchemgit.github.io/TASK.html

Best,

Mario

[Ahmed Zenhom]

Thank you so much I tried them and got most of the data I need. A final inquiry, where is the electronic energy and the zero point energy (ZPE) in those?

[Mario Schleep]

Just search in your output for "zero". You will find something like this:

 Temperature                      =   298.15K

 frequency scaling parameter      =   1.0000

 Zero-Point correction to Energy  =   23.723 kcal/mol  (  0.037806 au)

 Thermal correction to Energy     =   27.721 kcal/mol  (  0.044176 au)

 Thermal correction to Enthalpy   =   28.313 kcal/mol  (  0.045120 au)

 Total Entropy                    =   82.846 cal/mol-K

   - Translational                =   40.090 cal/mol-K (mol. weight = 113.9928)

   - Rotational                   =   27.228 cal/mol-K (symmetry #  =        1)

   - Vibrational                  =   15.528 cal/mol-K

 Cv (constant volume heat capacity) =   21.282 cal/mol-K

   - Translational                  =    2.979 cal/mol-K

   - Rotational                     =    2.979 cal/mol-K

   - Vibrational                    =   15.323 cal/mol-K