[Pw_forum] Problem in Variable-cell

Paolo Giannozzi giannozz at nest.sns.it
Fri Oct 22 17:00:17 CEST 2004

On Thursday 21 October 2004 23:56, Varadharajan Srinivasan wrote:

> After having relaxed the unit cell I take the relaxed structure and perform
> an scf calculation on it to obtain again the forces, stress and energy that
> vc-relax gives me anyway. (I made sure that I chose the structure 
> corresponding to the final energy and forces, ie. the structure reported
> before the final estimate). However, I obtain very different answers. 

- first of all, check if you can reproduce the results for the relaxed
  structure by passing the lattice parameters in input as in the variable-cell
  case, i.e. ibrav=0 and the lattice vectors
- check if the atomic positions in cartesian units are actually the same 
  in the two cases
- check that you used the same modified, or not modified, kinetic energy
  functional in both cases


Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
Piazza dei Cavalieri 7      I-56126 Pisa, Italy

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