excited state optimization

[aijitha_john]

Dear VASP users,
I am attempting to optimize the excited state of a system using the FERWE and FERDO flags. I've noticed that when performing the calculation with multiple k-points, the geometry appears incorrect. However, when I optimize the supercell using only the gamma point, the geometry looks reasonable. Is this a common occurrence? Additionally, during the excited state frequency calculation with the supercell (again using FERWE and FERDO), I am getting unusually large imaginary frequencies. Has this type of frequency calculation been tested before?

[marie-therese.huebsch]

Hi,

Not exactly sure what you are describing by "geometry appears incorrect". Could you please upload a minimal reproducible according to the forum guidelines?

Cheers,
Marie-Therese

[aijitha_john]

Dear Marie-Therese,
I have found that occupation is not constrained in the vasp calculations as given in INCAR. I am using vasp 6.4.2.
Is there any mistake in input or bug in vasp?

[marie-therese.huebsch]

Hi,

to my knowledge, FERWE and FERDO can only be used as an initialization (like MAGMOM) and not as a constraint. I guess you could use NELM=1 to simulate an ad hoc change of Fermi weights, but I don't have experience with that. I will ask around and get back to you.

Meanwhile, could you please attach the output and describe the goal of your calculation? Why do you want to constrain the occupations rather than determine them self-consistently? This is just for me to understand better what you aim for and find a way to make it happen in VASP.

Best regards,
Marie-Therese