[Pw_forum] about PW calculation of molecules

[patriot pershing]

dear please. i would explain somes calculations details concerning the
molecules pw calculation.
firstly when i have choose the ibrav= 0 i have specified the axis and
there is no problem in this step, as you have said the choice of alat
very big 100 bohrs is exactly to eliminate as posiible the interaction
of molecules with the other periodic image and no problem with memory.
second step, when i ask about about energy the goal is to determine
the energy per bond as well as forces
best regards

2010/2/9, Lorenzo Paulatto <paulatto at sissa.it>:
> On Tue, 09 Feb 2010 08:33:33 +0100, patriot pershing <science35 at gmail.com>
> wrote:
>> i have using espresso code to calculate the electronic structure and
>> properties of COHmolecule and to do this work i have choose the free
>> lattice
>
> Dear patriot,
> when you specify ibrav=0 (free axis) you also have to specify the axis...
> which was your choice?
>
>> with alat of 100 au (bohr) and i have positionned the atoms in
>> the center of lattice and when i have run the pw calculations this
>> don't work.
>
> I would be surprised if it did, it's a good idea to leave some empty space
> between periodic copies of the molecule, but 100 bohr is HUGE, probably
> you've just run out of memory. Anyway, what do you mean be "it does not
> work" precisely? Please remember to always supply as much information as
> possible when asking for help, this way you will get the best help in the
> shortest time.
>
>> in the same topics iw ould ask if it is possible with espresso to
>> determinate the binding energy between different molecules in ternairy
>>  molecules (3 atoms per molecule)
>
> Yes, you have to compute the energy of each component separately, then
> compare the sum with the energy of the components together.
>
> best regards
>
>
> --
> Lorenzo Paulatto
>
> *** Note: my affiliation has changed! please send future
> correspondence to: <Lorenzo.Paulatto at impmc.upmc.fr> ***
>
> post-doc @ IMPMC/UPMC - Université Paris 6
> phone: +33 (0)1 44 27 74 89
> www:   http://www-int.impmc.upmc.fr/~paulatto/
>
> previously:
> phd student @ SISSA  &  DEMOCRITOS (Trieste)
> phone: +39 040 3787 511
> www:   http://people.sissa.it/~paulatto/
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