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

Giuseppe Mattioli giuseppe.mattioli at ism.cnr.it
Thu Jun 4 15:31:58 CEST 2015

```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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> > Pw_forum at pwscf.org
> > http://pwscf.org/mailman/listinfo/pw_forum

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Giuseppe Mattioli
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