# [Pw_forum] [pw-forum]: Celldm(4) Celldm(5) Celldm(6)

Giovanni Cantele giovanni.cantele at spin.cnr.it
Fri Nov 20 13:02:12 CET 2015

```you do not need this information because to calculate for example cos(ab) you use the definition:
a = 1st lattice vector
b = 2d lattice vector

cos(ab) = a . b / Norm[a] / Norm[b] where . stands for dot product. Admittedly, as suggested by the last message, this is
something that you can work out by yourself, because it relies on basic solid state physics and
vector operations.

Giovanni

> On 20 Nov 2015, at 12:41, Francesco Pelizza <francesco.pelizza at strath.ac.uk> wrote:
>
> Thank you very much !!
>
> so cos (bc) cos(ac) cos(ab)
>
> a b c are in radians, degrees or something else?
>
>
> On 20/11/15 10:40, Giovanni Cantele wrote:
>> You can use the CELL_PARAMETERS card with ibrav=0 (so no need to compute the angles) or directly use the
>> definition of celldm(4), celldm(5), celldm(6) with ibrav=14 from Doc/INPUT_PW.txt:
>>
>> celldm(4)= cos(bc)
>>
>> b —> -0.004621093   2.150980697   0.080635052
>> c —> -0.031624028   0.077886584   1.892891072
>> celldm(4) = 0.0785376
>>
>> celldm(5)= cos(ac)=0.0165872
>>
>> celldm(6)=cos(ab)=-0.00341855
>>
>> Giovanni
>>
>>
>>
>>> On 20 Nov 2015, at 11:19, Francesco Pelizza <francesco.pelizza at strath.ac.uk> wrote:
>>>
>>> Hi dear Users and Developers,
>>>
>>> I really need a full explanation on how to get Celldm(4) Celldm(5)
>>> Celldm(6) from a VC-relaxation.
>>>
>>> The optimized structure of a system with angles between a-lat b-lat a
>>> c-lat not equals to 90° is given to me in some systems I am studying,
>>>
>>> But I can not find a way of putting this in a new input file.
>>>
>>> If I masure with xcrysden the inclination between periodic images, I got
>>> an angle that if i translate in the cosine value and put it into the
>>> input file, it does not give me the right angle when I open again the
>>> input file with xcrysden.
>>> Also a SCF calculation does not give a value identical or not even
>>> slightly different from the VC-rel calculation itself.
>>>
>>> So, How can I find out exactly Celldm(4) Celldm(5) Celldm(6) from this
>>> piece of output file?
>>>
>>> How do I put this in an input file being sure that quantum espresso will
>>> consider this value for building the lattice and doing the calculation
>>> properly ??
>>>
>>> Thank you very much for your time and patience
>>>
>>> Francesco Pelizza - PhD
>>> Strathclyde University (Glasgow)
>>>
>>> HERE you can find an output file as example
>>>
>>>
>>> Begin final coordinates
>>>      new unit-cell volume =   3435.21521 a.u.^3 (   509.04637 Ang^3 )
>>>
>>> CELL_PARAMETERS (alat=  9.35454172)
>>>    1.031703302  -0.002607611   0.034483284
>>>   -0.004621093   2.150980697   0.080635052
>>>   -0.031624028   0.077886584   1.892891072
>>>
>>> ATOMIC_POSITIONS (angstrom)
>>> H        2.323443642   3.458500775   8.048639166
>>> H        2.246157109   6.259499847   5.493082766
>>> H        2.238584163   4.257844190   0.859706518
>>> H        3.682576551   4.461248011   7.513953456
>>> H        3.660946840   5.289309420   5.076217107
>>> H        2.349858362   7.288089944   3.177035899
>>> H        3.698019711   6.240499825   2.728594264
>>> H        3.699705365   5.164845115   0.461710112
>>> F        2.578959296   7.555136884   0.769673740
>>> F        0.723629375   6.423372715   1.255939854
>>> F        2.384732674   3.966152941   3.106747236
>>> F        0.653462109   5.273905894   3.651911386
>>> F        2.644696706   2.964473519   5.656123191
>>> F        0.735387849   4.041727492   6.056045010
>>> F        0.629819356   5.581707632   8.226678603
>>> F        2.449175259   6.758487891   7.688004312
>>> F        4.791542403   2.350295723   2.918699000
>>> F        5.145230100   1.372558160   5.464114891
>>> H        3.794899005   0.874565766   1.033564982
>>> H        3.767987315   0.169480940   8.124815255
>>> F        1.620809549   1.343881537   2.353960638
>>> H        0.055376396   1.880995718   0.351068538
>>> F        1.746935882   0.059135078   4.717276882
>>> H        0.118749183   1.089942064   7.543474278
>>> H        0.038360119   8.721213695   5.604899727
>>> H        0.156416543   9.733931543   3.301761239
>>> F        1.606381831   9.555176644   7.542110410
>>> F        1.724803088  10.423382736   0.580085061
>>> H        3.762597275   9.742742557   6.180086748
>>> H        3.818806059  10.647160213   3.895291475
>>> F        4.834332727   8.431554403   8.190079715
>>> F        5.022683471   9.219462377   1.286641665
>>> C        4.861902815   0.149655116   8.161361938
>>> C        4.884761682   0.947642455   1.045408665
>>> C        0.337188869   0.143176054   4.742567438
>>> C        0.232687916   1.146022481   2.332101032
>>> C        2.593624135   4.380706568   7.522390456
>>> C        2.129082034   4.198114186   6.068998645
>>> C        2.035262317   5.577048626   8.307268734
>>> C        2.567916441   5.297168460   5.092510941
>>> C        2.062790705   5.205690370   3.651450062
>>> C        2.607997073   5.181809062   0.410338732
>>> C        2.124256003   6.343778231   1.286849130
>>> C        2.609613700   6.314467444   2.746950137
>>> C        0.204140831   9.649137133   7.505914552
>>> C        0.317897336  10.413912382   0.493174549
>>> C        4.910634377  10.672243764   3.875929892
>>> C        4.854146045   9.672373698   6.207264609
>>> End final coordinates
>>>
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--

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele

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