[Pw_forum] about vc-relax of graphite

[Paolo Giannozzi]

On Mar 6, 2007, at 3:22 , li niu wrote:

> Reducing dt from 100 to 20, I found "Entering Dynamics;  it = "  
> increasing .
> However in all the case when P equaled about  -59 (kbar) the code  
> stoped  and appeared
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      from checkallsym : error #         3
>      not orthogonal operation
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>   stopping ...
>
> What do you think about it ?

I think that you should read what is written in the users'guide:

---
\paragraph{\texttt{pw.x} stops during variable-cell optimization
in \texttt{checkallsym} with ``not orthogonal operation'' error.}

Variable-cell optimization may occasionally break the starting
symmetry of the cell. When this happens, the run is stopped
because the number of k-points calculated for the starting
configuration may no longer be suitable. Possible solutions:
\begin{itemize}
\item start with a nonsymmetric cell
\item use a symmetry-conserving algorithm: the Wentzcovitch
algorithm \\
(\texttt{cell\_dynamics='damp-w'}) shouldn't break the symmetry.
\end{itemize}
---
---
Paolo Giannozzi, Democritos and University of Udine, Italy