[QE-users] Applying assume_isolated="2D" to modified anatase surface

[pdelugas at sissa.it]

Hello Leon

is not very difficult, just a bit of work :-)

1. first I would conserve the chirality of the axes, so don't just 
switch the first and the third columns but cycle all the 3 of them

                                         1 --> 3, 3 --> 2, 2 --> 1

2.  replace the second row of cell-parameter with  (0.00000, 
modulus_second_row,  0.000000)  and third with  (0.000000,  cos (a2-a3) 
* modulus_third_row, sin(a2-a3)*modulus_third_row )

     cos(a2-a3) is the cosine between the second and third rows of 
CELL_PARAMETERS

3. run pw.x with this input, just until it prints the cartesian 
coordinates in the  output ( its few seconds ), copy those coordinates 
and put them in your input, taking care to replace also crystal with alat

4. replace the third row of cell parameters with  (0.0000, 0.0000,  
9.00000) and you should have done. Better check though

hope this solves your problem

Pietro

On 02/12/22 15:59, Léon Luntadila Lufungula wrote:
>
> Hi Pietro,
>
> Thank you for the quick answer! As I understood it I switched the 1^st 
> and 3^rd column of the CELL_PARAMETERS array so that the surface is in 
> the XY plane and not the ZY plane and now the code does not give the 
> “Error in routine vloc_of_g (1):” error, however, the “2D CODE WILL 
> NOT WORK, 2D MATERIAL NOT IN X-Y PLANE!!” error remains… I guess this 
> might indeed be due to the non-orthogonal cell, but I was wondering if 
> it is possible to adjust the cell in any way so that it is orthogonal 
> without fundamentally changing the system properties? This might be a 
> very stupid question but I’m still a little bit new in doing 
> calculations on solid state systems, so I don’t know what is and what 
> isn’t possible in such a case. My instinct says it might not be 
> physically possible to create an orthogonal cell which maintains the 
> symmetry of the surface, but if it could be possible this would be 
> very useful for me as I also have had other problems which would have 
> been resolved if my cell was orthogonal…
>
> Kind regards,
>
> Léon Luntadila Lufungula
>
> PhD student
>
> University of Antwerp
>
>
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