Question about Isotope Mass Specification in i-PI with VASP for PIMD

[Mia Amelia]

Hi all,

I am trying to use i-PI with VASP for PIMD with different isotopes. I have modified the POMASS for deuterium in the POTCAR file. Does modifying POMASS in POTCAR have any effect, or do I need to specify the isotope mass in the i-PI input.xml file instead?

I saw on forums that when using i-PI with CP2K, isotope masses need to be specified in the input.xml file. Is it the same case for VASP?

Thanks for your help.

Best regards,
Mia Amelia

[Mariana Rossi]

Dear Mia Amelia,

There is no effect at all if you only modify VASP inputs for the mass. You must input the mass in the i-PI xml input file (in the initialize block) or just write D instead of H in the initial geometry that *i-PI* is reading. Then it will work.

Any client of i-PI works only as a force/energy/stress provider, i-PI instead controls all the dynamics, so it is the same for all clients.

See you,

Mariana

[Mia Amelia]

Dear Mariana,

Thank you very much for your clear and detailed explanation. Your guidance on modifying the mass in the i-PI xml input file and the initial geometry really helped me understand how i-PI manages the dynamics and why changing VASP inputs alone has no effect.

I appreciate your time and patience in clarifying this for me. This will greatly help me move forward with my simulations.

Thanks again and hope to stay in touch!

Best regards,
Mia Amelia