[Pw_forum] supercell and vacuum

[Daniele Stradi]

Hi Lorenzo,

VNL saves the atomic coordinates of the system in the "{crystal}" form.

 From the input file description page 
(/http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html/), 
card: ATOMIC POSITIONS:

/crystal : atomic positions are in crystal coordinates, i.e.//
//          in relative coordinates of the primitive lattice//
//          vectors as defined either in card CELL_PARAMETERS//
//          or via the ibrav + celldm / a,b,c... variables/

Therefore, if one modifies the lattice vectors in a PW input file 
exported from VNL, the atomic coordinates are also indirectly modified.

You should add the vacuum gap from within VNL before exporting the PW 
input file.

Cheers,

Daniele

-- 
-------------------------------------------------------------
Daniele Stradi, PhD
Scientific Specialist
QuantumWise A/S
Tel: +45 699 01 888
Mail: daniele.stradi at quantumwise.com
Skype: daniele.stradḯ
Linkedin: https://www.linkedin.com/in/daniele-stradi-23797137
-------------------------------------------------------------

On 09/28/2016 08:23 AM, Jess Wellendorff wrote:
>
> Dear Lorenzo.
>
> If this is indeed a problem related to Virtual NanoLab, I will be 
> happy to try to help you out. Could you give more details on what you 
> did in VNL? And preferably also attach the generated PWscf input file.
>
> -- 
> Jess Wellendorff
> Scientific Specialist
> QuantumWise A/S
> Fruebjergvej 3, Postbox 4
> 2100 Copenhagen, Denmark
> Web:www.quantumwise.com
> Email:jess.wellendorff at quantumwise.com
> Tel:   +45 69901888
> --
>
>
>
> On 09/28/2016 08:18 AM, Stefano de Gironcoli wrote:
>> Looks like a problem in how you 'add vacuum' In your virtual nanolab 
>> step. Difficult to say without further information.
>>
>> stefano
>> (sent from my phone)
>>
>> On 28 Sep 2016, at 06:51, Lorenzo Pedrazzetti 
>> <lorenzo.pedrazzetti at polimi.it 
>> <mailto:lorenzo.pedrazzetti at polimi.it>> wrote:
>>
>>> Goodmorning qe community,
>>> I created an interface metal/semic by using virtual nanolab; when I 
>>> come to check my structure with xcrysden I notice that, when vacuum 
>>> is added enlarging the corresponding CELL_PARAMETERS component, all 
>>> my atoms move along that direction, effectively expanding the cell 
>>> instead of introducing vacuum layers.
>>> Where do I mess up? I thought the system is such that fixed celldm 
>>> () and ATOMIC_POSITIONS all atoms should not move anymore.
>>> Thanks, have a nice day.
>>>
>>> Sent from my ASUS
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>>
>>
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>
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