The ABINIT Users Mailing List ( CLOSED )

["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi,

First I would say that your order to perform cell optimization looks
correct as long as you do not await phase change under stress. Yet it
would probably be more efficient to perform directly a global
optimization of both atomic and cristal coordinate.
Second, I can not comment on correctness of experimental ratio. But
using your procedure you will likely fall close to at least a DFT
local minima. So, as long as DFT is correct, your approach is OK.

regards

PMA

On 4/30/07, taoj0003@ntu.edu.sg <taoj0003@ntu.edu.sg> wrote:
> when using abinit(maybe also some other software) to optimize the structure, 
> a problem really puzzled me-what is the best procedure?
>
> let me make this more clearly. To optimize the structure, here is one 
> procedure:
>
> First, if there are more than one atom in the cell, we need feagure out all of the 
> optimized coordinations. Abinit make this part easy to do thanks to the 
> "ionmov".
>
> Then we need to optimize lattice constants.But how? Just keep their 
> experimental ratio and optimize the volume or adjust every values (a, b ,and 
> c) near the experiment values until it reached the lowest total energy? If 
> you do it the first way, I may ask, is the experiemnt ratio correct for using 
> in the simulation?( because, simulation always deviates from experiment 
> somehow).
>
> The second part really make me crazy. There are also some cross section 
> effect. And even should the seccond part go first?


--
Pierre-Matthieu Anglade