The ABINIT Users Mailing List ( CLOSED )

[Hongyi Zhao <hongyi.zhao@gmail.com>]

On Thu, Apr 19, 2007 at 01:06:57AM +0800, LEE Chin Chai wrote:
> Hi HongYi,
> 
> To get the rpim vector defined by abinit, you can do a 45 degrees of 
> clockwise rotation(you can use a 2D rotation matrix)of the rpim defined in 
> the vasp course.  Hope it helps. It is really arbitrary of how you define 
> your rpim parameter as long as it reproduces your slab correctly.

Thouth I can get the *rprim* vector defined by abinit through the way 
you mentioned above, but I still have the following questions:

1. If I use the *rprim* in the form defined by abinit, I can represent 
all the atoms in the (1 0 0) plane with integral linear combinations of 
the *rprim*;  but in the case of the vasp course, I think in order to 
represent all the atoms in the (1 0 0) plane, we must use real linear 
combinations of the corresponding *rprim*.  Is this true?

2. I still cann't understand the following line's meaning I excerpt from 
the Abinit's tutorial:

---------
In order to study the Aluminum (100) surface, we will have to set up a 
supercell representing a slab. This supercell should be chosen as to be 
compatible with the primitive surface unit cell.
The corresponding directions are [-1 1 0] and [1 1 0]. The direction 
perpendicular to the surface is [0 0 1]. There is no primitive cell of 
bulk aluminum based on these vectors, but a doubled cell. We will first 
compute the total energy associated with this doubled cell. This is not 
strictly needed, but it is a valuable intermediate step towards the 
study of the surface.
---------

Let me tell you the problems puzzlling my brains in the above paragraph:

a). It says that *The corresponding directions are [-1 1 0] and [1 1 
0]*, what dose this mean?  I mean, these two directions don't belong to 
(100) surface at all, in fact, they belong to (001).

b). What's the mean by saying that *This supercell should be chosen as 
to be·compatible with the primitive surface unit cell.*, would you give 
me more detailed descriptions about this thing?

Thanks in advance.
---
Hongyi Zhao
GnuPG DSA: 0xD108493B