| Re: How to apply periodic boundary conditions ( No.1 )|
- Date: 2019/01/18 01:25
- Name: Naoya Yamaguchi
OpenMX always considers periodic boundary conditions along a-, b-, and c-axes except some methods, such as NEGF and ESM. For example, slab calculations are usually performed by inserting a vacuum region with an enough width to remove influence of image cells through "Atoms.UnitVectors" as you said.
| Re: How to apply periodic boundary conditions ( No.2 )|
- Date: 2019/01/18 13:53
- Name: sanjeev
Thank you very much for your reply. But still my doubt is not clear.
In the above mentioned paper the author has mentioned that he made Y & Z directions nonperiodic.
My question is that, How he made Y & Z nonperiodic and X as periodic. while, openmx consider all x,y,z
directions as periodic.
Now suppose I want to simulate graphene fragments with a supercell dimensions
x= 10, y=50, z=50, for this I set.
10.000 0.000 0.000
0.000 50.000 0.000
0.000 0.000 50.000
it means I have created a vacuum in Y & Z directions, but how it mean that my calculations is periodic in x direction only.
It is right if I say that my calculations are periodic in all x,y,z directions
Thanking in advance.
| Re: How to apply periodic boundary conditions ( No.3 )|
- Date: 2019/01/19 02:01
- Name: Naoya Yamaguchi
- Dear Sanjeev,
>My question is that, How he made Y & Z nonperiodic and X as periodic. while, openmx consider all x,y,z
>directions as periodic.
Now I read the paper and I guess that they did band calculations using OpenMX 3.4 (or 3.5) and inserted a vacuum region, for example:
3.11 0.0 0.0
0.0 L 0.0
0.0 0.0 L
, where L>20.
>Now suppose I want to simulate graphene fragments with a supercell dimensions
>x= 10, y=50, z=50, for this I set.
I think it is right for calculations of one-dimensional materials such as nanoribbons.
| Re: How to apply periodic boundary conditions ( No.4 )|
- Date: 2019/02/08 23:03
- Name: Kylin <Kylincaster@foxmail.com>
- Dear all,
The periodicity in OpenMX calculation is automatically determined and straightforwardly shown in the screen log files as "The system is molecule|chain|slab|bulk" will be displayed as in the screen log file, representing 0D|1D|2D and 3D system respectively. So be careful to check periodicity in our calculation which was determined by PAOs cut-off (Rc) and dimensions of box sizes. It becomes non-periodic only with 2Rc > box_size.
Moreover, the calculation of Uele was based on FFT which is only valid for 3D periodicity box which may induce some problems with the low dimensional material studies. So a large interlayer vacuum spacing is necessary or taking the effective screening medium (ESM) method