On 06/14/2011 05:04 PM, Marcos Veríssimo Alves wrote:
Sorry,
I made a mistake here. It should be K=(0.5, -0.5, 0) instead.
Marcos
2011/6/14 Marcos Veríssimo Alves <[email protected]
<mailto:[email protected]>>
It has nothing to do with Hydrogens in the system. As a matter of
fact, hydrogens would open the gap - it would be graphane, not
graphene. The input seems fine to me, and it it most likely because
your specification of band lines is incorrect. If you choose
BandLinesScale ReciprocalLatticeVectors
then G=(0,0,0), K=(0,-0.5,0) and M=(0.5,0,0) (Check the figure on
page 25 of Saito and Dresselhaus's book).
I've checked the above book. It's right of course in theory. But I think
when we construct this structure for calculation with some software,
say, siesta, we should consider some rules which will facilitate the
identification of space group and symmetry information.
The original fdf file posted in this thread is strictly conform with
the informations given in Saito and Dresselhaus's book. But I think
this is just the reason that may arise some errors when runing within
siesta. For detail, in Saito and Dresselhaus's book, and this fdf file
posted in this thread, the x-->y and a --> b have different Clockwise
direction. This will put the lattice vectors in a left-hand oriented
system, while the reference Cartesian system is right-hand oriented.
Perhaps this will give some difficulties when finding the correct space
group information.
I don't know whether this is the reason that caused the problems
mentioned by OP, but I suggest change the original fdf as follows for
the block LatticeVectors:
-----------------
%block LatticeVectors
0.86600 -0.500000 0.00000
0.86600 0.500000 0.00000
0.00000 0.00 10.0000
%endblock LatticeVectors
-----------------
In this way, both the x->y->z and a->b->c will comply with right-hand
oriented system.
Furthermore, I've checked the original fdf file in this thread with
GDIS, when I generate a cif file based on this fdf file, the result is
as follows:
-----------
data_block_1
_audit_creation_date 'Sun Jun 26 17:27:02 2011'
_audit_creation_method 'generated by GDIS v0.99'
_cell_length_a 2.4599
_cell_length_b 2.4599
_cell_length_c 24.6000
_cell_angle_alpha 90.00
_cell_angle_beta 90.00
_cell_angle_gamma -60.00
_symmetry_space_group_name_H-M 'P 1'
_symmetry_Int_Tables_number 1
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
C 0.000000 0.000000 0.000000
C 0.333343 0.333343 0.000000
-----------
I checked this cif with publCIF (version 1.9.9_c)
(http://www.iucr.org/resources/cif/software/publcif ), it told me the
following error in this cif file: _cell_angle_gamma value (-60.00) below
minium (0)
Furthermore, if I import this cif into other softwares, say, Materials
Studio, it will give a wrong spacegroup information.
Please correct me if I'm wrong, thanks in advance.
Regards.
>
Best regards,
Marcos
On Tue, Jun 14, 2011 at 9:11 AM, deepak srinivasan
<[email protected] <mailto:[email protected]>> wrote:
Hi
i think this is a sample program coming along with siesta
as for as the band gap being large it is due to the carbons not
being terminated by hydrogens or any other such atom
Terminate the two atoms with hydrogen and observe the difference
--
regards
deepak
3rd Year Under Graduate
Electronics Design and Manufacturing
IIIT (D&M),Kancheepuram
IIT Madras Campus,Chennai
--
Hongyi Zhao <[email protected]>
Institute of Semiconductors, Chinese Academy of Sciences
GnuPG DSA: 0xD108493
