[Pw_forum] Convergence problems on supercell calculation of MgB_2

[张 洪彬]

Dear all:
  I am now doing some calculation of 2×2×1 supercell of MgB_2 without any 
atom moved, however, after 100 iterations the package tell me that the 
convergence has NOT been achieved, while with 3×3×1 supercell I had 
successfully got scf caculation done. The E_thr is 1.0E-8, while the 
smallest estimated energy accuracy is 2.0E-8. The package I used for 2×2 
caculation is the latest version, while 3×3‘s is not. Is there any 
comment on this and advice on how to improve the calculation?
Thank you.
Regards.

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