Assistance with Excited State Calculations Using FERWE and FERDO Tags in VASP
Dear VASP Team,
I am currently working on excited state calculations in VASP. Specifically, I am attempting to excite an electron from the ground state (GS) to the excited state (ES) using the FERWE and FERDO tags. However, I am encountering difficulties.
While my calculations run without errors, the expected electron excitation does not occur. Upon examining the OUTCAR file, I notice that the number of electrons in the conduction band remains unchanged from the ground state. It seems that the excitation I am trying to enforce is not being reflected in the results.
To achieve this, I considered the following settings for the FERWE and FERDO tags:
FERWE = [O_UP-1]*1.0 1*0.0 1*1.0 [U_UP-1]*0.0 <repeated N_K times>
FERDO = [O_DN]*1.0 [U_DN]*0.0 <repeated N_K times>
Here, O_UP and O_DN represent the number of occupied spin-up and spin-down states, while U_UP and U_DN represent the unoccupied spin-up and spin-down states. Despite using these settings, the excitation does not seem to occur.
To resolve this issue, I would like to gain a deeper understanding of the proper usage of VASP for excited state calculations. Specifically:
How should the FERWE and FERDO tags be used to enforce electron excitation?
Are there common pitfalls or additional parameters I should consider when attempting such calculations?
regards,
Priyanka