[Pw_forum] Unit cell and atomic position optimization

[John Teller]

Dear Lazaro,

>I got pwscf running on a SUN cluster a while ago and I have started
>doing some optimization of both unit cell parameters and atomic
>positions in a hexagonal system (hydroxyapatite) to compare with LCAO
>results. I have a problem similar to the one posted by Yanming Ma in >his 
>last message. That is: pwscf does not converge to the a given >pressure.
>I tried increasing the mass of the unit cell to damp the oscillations
>between negative and positive values of the pressure but it did not work
>neither. I would be interested in any suggestions on how to perform
>relaxation of unit cell parameters and atomic positions at the same time
>in non-cubic systems using pwscf.

Actually, I did not state that pwscf does not converge to a given pressure. 
I just mentioned that by comparing with other ab initio plane wave code 
(VASP or ABINIT), PWSCF may be less convient to get the EOS for non-cubic 
system, based on my limited knowledges on PWSCF. So I sent my questions on 
how to get the proper input parameters when I try to do geometry minisation. 
I also want to make sure what kind of MD ('cm','nm','mm')is the best to do 
geometry minisation. But nobody reply me except Guido