[Pw_forum] vc_relax problem

[Paolo Giannozzi]

On Sep 29, 2009, at 10:53 , Marcello Rosini wrote:

> I am performing a variable cell relaxaion with pw.x 4.1. In  
> particular I
> put the keyword cell_dofree='z' [...] It seems to me that the program
> does not care for this constraint and relaxes all the cell parameters.

it seems to other people as well:
http://www.democritos.it/pipermail/pw_forum/2009-August/013979.html

>      from scale_h : error #         1
>      Not enough space allocated for radial FFT: try restarting with  
> a larger cell_factor.

do what it suggests, or else restart from an initial cell (the one you
provide in input) that is closer to what you found during relaxation.
Plane waves and G-vectors are calculated for the input cell,
rescaled for the new cell as the cell changes. The maximum
value of |G| thus changes during optimization/molecular dynamics.
If it exceeds the maximum allowed value, the code will stop.

Paolo
---
Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222