Hi, Heiko Dumlich Thank you for your kind reply. I have modified the input file for Siesta, and it is attached. I am testing the input file if it works. I have two questions.
a) Because graphene is a 2D material, I just want to know whether the unit
cell defined in the input file is right or not?
b) The variable LatticeConstant is set by an experimental value. Maybe when
I have successfully optimized the geometry,
the LatticeConstant is changed, then I should set which one to be the
LatticeConstant, the experimental one, or the optimized one?
Any comment or suggestion is appreciated.
Best
Fei Mao
-----原始邮件-----
发件人: "Heiko Dumlich" <[email protected]>
发送时间: 2012年11月8日 星期四
收件人: [email protected]
抄送:
主题: Re: [SIESTA-L] Problem of graphene sheet optimization
Dear Fei Mao,
your unit cell does not periodically repeat the graphene structure. Further
none of your calculations is converged. You should think about your unit cell
LatticeConstant 2.44 Ang
%block LatticeVectors
13.000 0.000 0.000
0.000 13.000 0.000
0.000 0.000 4.100
%endblock LatticeVectors
and optimize the values to create an infinite graphene sheet. Then the
optimization becomes far less demanding, as no dangling bonds exist at the
edge. If you desire dangling bonds at the edge, you have to at least converge
your calculations to a decent value, which "siesta: 99 -8321.6798
-8318.5587 -8318.5639 0.9802 -4.8893" definitely is not true for
dDmax=0.9802.
Good Luck
Heiko Dumlich
On 11/08/2012 09:50 AM, 毛飞 wrote:
Hi, all
Has anyone ever tried to get a well converged geometry optimization of pure
graphene, which is not passivated with any hydrogen atoms in the edge of
graphene layer. In that case, the carbon atoms in the edge of graphene are kept
with dangling bonds.
I have done this job within many codes, and all failed. I find it is very hard
to do this, but in many published scientific papers, there are the energy band
analysis of pure graphene (and sometimes adsorbed with adatom), such as DOS, or
PDOS. It is very amazing, it seems that these authors have the pure graphene
relaxed fully. Or they obtain the band structure with not fully relaxed
graphene sheet. Do you have any ideas?
I attach the input and output files for optimizing the pure graphene by using
Siesta codes (in order to obtain the converged geometry optimization, I have
increased the MeshCutoff to 400 Ry, it still does not work).
Any comment or suggestion is appreciated. Thank you.
Fei Mao
Beijing Normal University
--
Heiko Dumlich
Freie Universität Berlin
Fachbereich Physik - AG Reich
Arnimallee 14
D-14195 Berlin
GERMANY
Phone: +49-30-838 56157
graphene.fdf
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