[Pw_forum] Query about restarting vc-relax

[Paolo Giannozzi]

On Apr 17, 2008, at 13:48 , Phillip English wrote:

> However as soon as I restarted, the energy blew out. Looking at the  
> cell parameters, they too blew out, and visualising the structure  
> showed that the cell was indeed expanding quite rapidly. When I  
> looked at the output more closely, it seemed like the starting cell  
> parameters for the restarted calculation were still being  
> calculated by the program according to the specified ‘ibrav’ and  
> ‘celldm’ values, rather than restarting with the cell parameters  
> that had relaxed from the previous calculation. This is what I  
> supposed caused the ‘explosion’. It seems strange to me that while  
> the atomic positions are read in correctly, the cell parameters are  
> not.
>

restarting from a variable-cell optimization / molecular dynamics  
run ? not
sure it works properly. If nobody has ever verified it, it is  
unlikely that it works.
The only parts of the distribution that typically work are either the  
most frequently
used, or those used by people willing to, and able to, improve the code.
> So, my question after that long preamble; do you need to manually  
> re-enter the cell parameters using the ‘CELL_PARAMETERS’ flag when  
> restarting a vc-relax calculation?
>
not unlikely, but it might not be sufficient

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