[Wien] regarding k-mesh and tolf

[chin Sabsu]

Dear Stefaan Sir
Below are my updates:
A. For mesh sizeI got your point and in all different distorted structure (with different inequivalent atoms) I am having the same number of electrons while the number of inequivalent atoms are different. NE varies from 154 to 616(1x1x1 cell) to 4928 (2x2x2 cell).So I will divide xxx numk by 4 and 32 in 1x1x1 and 2x2x2 supercell structure. Thanks for this excellent recommendation!!!For 2x2x2 supercell in phonopy calculations, we need to go for mpi jobs for certain cases!!

B. Now I have done some tests for my cubic perovskite and below are my observations:
B1. For tolf 5 and -fc1 I for FOR003 = ~4 mRy/bohr  with band gap ~0.1 eV
B2. For tolf 2 and -fc 0.1 forces are almost same. and the band gap is still ~0.1ev

B3. Now to reduce the forces less then 0.1mRy/bohr, I reduced the tolf to 0.5 and -fc 0.1 - 0.01. I got forces at the desired accurecy but the band gap vanished and the system becomes metallic. The experimentally reported band gap is 1.2eV
I used RKMAX 8, numk 2000, vxc 19.
What is your suggestion for point number B, why I am getting the system metallic?Can I use this relaxed structure for Phonopy?
Kind regards
Chin S.
 
For tolf

 
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