[Pw_forum] VC-relaxation celldm 4-5-6

[Nicola Marzari]

Francesco - to add to Giuseppe's explanation - a lot of info is here:
http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html

and if you click on ibrav:
http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#idp82064

you'll get all the explanations.

I also think it would be helpful to have a few more info written out 
explicitly
by the code - maybe at a certain point we could probe this forum to see what
is most needed by the users.

				nicola




On 04/06/2015 15:31, Giuseppe Mattioli wrote:
>
> Dear Francesco
>
>> CELL_PARAMETERS (alat=  9.37304158)
>>      0.998026269   0.000004734  -0.013893833
>>      0.000009261   1.956757114  -0.000006827
>>     -0.117999199  -0.000006751   1.878825464
>
> these should be the projections of a b and c on the orthogonal xyz axes (first row a, ...), expressed in {alat} units. With a few calculations you
> should be able to extract the angles, but, admittedly, it would be useful to have the values in the output. If you are lazy like me, then you can open
> the pw output with xcrysden, replicate the unit cell and measure the angle between the replicas.
> HTH
> Giuseppe
>
> On Thursday, June 04, 2015 02:06:30 PM Francesco Pelizza wrote:
>> I mean I need help to know where I can find the information from which I
>> can calculate "celldm 4-5-6".
>>
>> Begin final coordinates
>>        new unit-cell volume =    725.36965 a.u.^3 (   107.48869 Ang^3 )
>>
>> CELL_PARAMETERS (alat= 16.21385015)
>>      1.004657057   0.000000000   0.000000000
>>      0.000000000   0.559585576   0.000000000
>>      0.000000000   0.000000000   0.302702891
>>
>> FROM this grid of result I assume Alpha, Beta and Gamma are all 0 (90°).
>>
>>
>> Begin final coordinates
>>        new unit-cell volume =   3018.74953 a.u.^3 (   447.33252 Ang^3 )
>>
>> CELL_PARAMETERS (alat=  9.37304158)
>>      0.998026269   0.000004734  -0.013893833
>>      0.000009261   1.956757114  -0.000006827
>>     -0.117999199  -0.000006751   1.878825464
>>
>> BUT from this grid, I guess Alpha, Beta and Gamma are not all equal to 0.
>>
>> And I do not know how to get these values, and never found the
>> explanation somewhere in many tutorials I downloaded.
>>
>> I know is an extremely easy question, but I still do not know the output
>> format for getting Alpha, Beta and Gamma.
>>
>> Sorry for my lack of knowledge.
>>
>> I am still stuck
>>
>> On 04/06/15 13:46, Paolo Giannozzi wrote:
>>> On Thu, Jun 4, 2015 at 2:20 PM, Francesco Pelizza
>>> <francesco.pelizza at strath.ac.uk
>>>
>>> <mailto:francesco.pelizza at strath.ac.uk>> wrote:
>>>      I need help please
>>>
>>> you need help to compute three angles between three vectors? Sure?
>>>
>>>
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>
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>     Giuseppe Mattioli
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-- 

----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL