[Pw_forum] Is the "cell_dofree" functionality fully implemented in Espresso 4.0.x?

[Serge Nakhmanson]

Dear All,

Is "cell_dofree" feature in &CELL completely implemented
in Espresso 4.0.x? I have checked out the previous forum
postings but I think that the question I have below has
not been brought up before.

When I had to do my own modifications to achieve a similar
goal in Espresso 3.x, I ended up changing vcsmd.f90 (to pin
certain lattice consts) and in stress.f90 (to zero out some
stress tensor components).

In the current version everything seems to be conveniently
controlled through the use if "iforceh" parameter set in
input.f90. However, when I trace how it is used, I can see
something similar to what I did in vcsmd.f90 and nothing in
stress.f90 or any other place that deals with stresses.

So what happens, as it seems to me, is that this algorithm
works (i.e., keeps certain lattice consts fixed during a
vc-relax run) but never finishes, even when the appropriate
stress tensor components get relaxed (e.g., to zero). Since
the unneeded stress tensor components (as it seems) do not
get zeroed out, the

   ( ABS( sigma(i,j) ) * uakbar < epsp )

condition in vcsmd.f90 is never reached. Or am I missing
something?

Would appreciate any sage comments on this.

THX,

Serge

-- 
*********************************************************
  Serge M. Nakhmanson               phone: (630) 252-5205
  Assistant Scientist                 fax: (630) 252-4798
  MSD-212, Rm. C-224
  Argonne National Laboratory
  9700 S. Cass Ave.
  Argonne, IL 60439
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