[QE-users] Essential of doing vc-relax - regarding

[SAURAV LAHIRI]

Hi singaravelan,
    relax calculation is done mostly in 2d systems where we need to find
the optimized atomic coordinates.  In your case vc-relax is the best. But
there is nothing like which is superior. It depends on your system. Thank
you.
*SAURAV LAHIRI*
*Junior Research Fellow (JRF)*
*Condensed Matter Physics Laboratory (CMPL)*
*Department of Physics*
*IIT(ISM) Dhanbad*



On Fri, Apr 16, 2021 at 8:16 PM singaravelan T R <trsingaravelan27 at gmail.com>
wrote:

> Dear all,
> I like to know the difference between vc-relax (*optimize lattice
> constant and atomic positions)  *and relax(*optimize the atomic positions
> alone*). other than the bold words, i like to know further.? and also
> When to perform vc-relax?
> Is vc-relax superior over relax part. ?
> I have two views which are correct, I don't know, following are those:
> please help me here.
> 1) Suppose if i am doing vc relax for silicon and i got some cell
> parameters and atomic position. Is that the atomic position and lattice
> constant I should use for further scf calculation? (I am saying No need to
> do lattice constant optimization.)
>  *(or)*
> 2) I haven't done vc-relax, just done a relax calculation with reference
> lattice constant, i used that atomic position in my further calculation,
> proceeded with ecutwfc optimization, then kpoint, lattice constant ? (Not
> worried on vc relax).
> Which is correct?
> with thanks,
> Singaravelan T R
> Research Scholar,
> University of Madras
>
>
>
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