[Pw_forum] Question about vc-relax

[Anand Chandra]

Hi Joshua,

If you are running a vc-relax calculation, the stress after each relaxation
step will be written in the output file (see tag tstress). Is the stress
less than the default threshold (see tag press_conv_thr)?

Also, for optimizing lattice parameters of a 2D material you should use the
tag cell_dofree="2Dxy" .

Regards,
Anand Chandrasekaran
Post-doctoral researher
Materials Research Center
Indian Institute of Science

On Fri, Oct 14, 2016 at 10:44 PM, Joshua Young <jyoung11509 at gmail.com>
wrote:

> Hi QE community,
>
> I am attempting to relax the lattice parameters and internal atomic
> positions of monolayer MoS2 using a variable cell relaxation. However,
> although the atom positions will change over the course of the calculation,
> the lattice parameters do not even though the calculation converges. I have
> attached my input file here, as well as the atomic positions and lattice
> parameters output for five steps of the calculation. I am including van der
> Waals correction, spin-orbit coupling, and using fully relativistic
> pseudopotentials.
>
> Could this be because I have started from lattice parameters which are
> close to the equilibrium values of MoS2? Or do I simply have a tag wrong in
> the input file?
>
> Any help would be greatly appreciated.
>
> Thank you,
> Joshua Young, PhD
> Postdoctoral Research Associate
> Naval Research Laboratory
> Washington, DC
>
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