[QE-users] band convergece problem in charged system

[Leo Yang]

Dear QE users:

I try to use QE-6.4.1 to simulate  as single molecule. The system is built in large super cell, and total_charge=-4  is added to input file leading to charged system. When I do the convergence test in term of the super cell size (20 Angs - 30 Angs ), the variation for total energy is small: -1038.6784 Ry for 20 Angs and 1038.7388 Ry for 30 Angs. But the band energy and Fermi energy (5.23 ev to 3.08 ev) shift visibly. The problem is that the band gap between band 104 (occupied) and 105 (unoccupied) become smaller with the increase of size (about 0.81 ev change to 0.11 ev). It seems the band gap is gradually disappear, which confuses me so much. The input file is attached with this email. It will be very appreciated if you can solve this for me. Thank you.




Best wishes

Yang Zhou




------

Yang Zhou

PhD student

University of Leeds

United Kingdom
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