[Wien] Non convergence of LiNiO2

[shamik chakrabarti]

Dear Wien2k users,

                     I am trying to simulate LiNiO2. I have achieved volume
optimization & c/a optimization so far, however not able to achieve the
coordinate convergence by using,
runsp_lapw -orb -fc 1.0 -ec 0.0001 -cc 0.0001 -min. I can list the possible
causes of non convergence as below;
(1) Structure is wrong: I think the structure is correct as both the unit
cell structure used earlier and
experimental XRD matches well as can be seen by using Vesta.
(2) Wrong Exc or GGA+U: I have used GGA+U with U=2.45 eV for Ni+3 using the
reported value of U in earlier calculations. As it is a layered structure,
I have also tried,
runsp_lapw -orb -nlvdw -fc 1.0 -ec 0.0001 -cc 0.0001 -min, however both
GGA+U & nlvdw+GGA+U failed to converge.
(3) No. of K-points: I have used 280 k-points per unit cell contains 4
atoms/unit cell.

The calculations are still running & reached upto 100 iterations without
any sign of convergence. I have tried to converge before adding -min to the
script by using runsp_lapw -orb -ec 0.0001 -cc 0.0001 for 400 iterations.
However the simulation do not converge. I am sending the struct file for
your concern.

Looking forward to listen from you.

with regards,
-- 
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India
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