Dear Yang,
I have no clue how the Martyna-Tuckerman correction works but usually one
has problems with systems having such a large total charge since the total
cell needs to be neutral. Some terms are in fact calculated for a charge
neutral
system resulting in a total potential which has a curvature as if there
would be
a homogeneous background charge. This constant curvature leads to a
potential energy minimum in the vacuum space between the repeated cells.
If you increase the cell this minimum goes down in energy and, at some
point,
crosses the Fermi energy and gets occupied.
Long story short:
I have no clue but are you sure that Martyna-Tuckerman correction works
correctly for charged systems?
Is the LUMO really a state of the molecule and not from a state in the
vacuum?
You could check if everything works as intended for a neutral system...
Regards
Thomas
On 10/2/19 1:46 PM, Leo Yang wrote:
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
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig
Tel: +49 (0)341 97 36456
email: [email protected]
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
