Hello,
I am working on a complex structure that requires passivation of dangling bonds in the bottom layer. However, H with 1.5 e is not available in VASP, I use H with 1.25 e for some dangling bonds. However, this results in a fractional total charge (1977.5 e in the system). What are some of the important considerations when running systems with a fractional total charge?
Thank you!
Dear Serenity_3,
thank you for asking for support via the official VASP forum.
I am not an expert for fractional charged systems but let me try to give a first few hints.
1) As far as I can see there are H pseudo-potentials available also fro 1.5 electrons:
ls ~/git/vasp/POTCAR/PBE_64/H*
H/ H.33/ H.5/ H.66/ H1.25/ H1.5/ H1.75/ H_GW/ H_h/ H_s/ He_AE/ Hf/ Hf_sv/ Hg/ Ho/ Ho_h/
H.25/ H.42/ H.58/ H.75/ H1.33/ H1.66/ H_AE/ H_GW_new/ H_h_GW/ He/ He_GW/ Hf_pv/ Hf_sv_GW/ Hg_sv_GW/ Ho_3/
Can you double check and if possible receive the latest set of POTCARs from the website?
2) Fractional charged system should be no problem in VASP
3) If your system is indeed charged then only electrostatics effects will make your life very hard when converging the system etc. See also this section of the wiki for some help: wiki/index.php/Electrostatic_corrections . In general the calculation should work as soon as care has been taken in some way of these effects.
Maybe there are also other users in the forum who are more experienced regarding this topic and can help you further.
Best regards,
Alex