[Pw_forum] changing total energy due to changing ibrav

[Duy Le]

Should you compare total energy per atom or total energy per unit volume?
Of course, you have to use well-converged cutoff and k-point sampling.
----------------------------------------------------
Duy Le
Postdoctoral Associate
Department of Physics
University of Central Florida.
Website: http://www.physics.ucf.edu/~dle


On Wed, Jan 16, 2013 at 3:25 AM, Lorenzo Paulatto <
lorenzo.paulatto at impmc.upmc.fr> wrote:

> On 16 January 2013 02:33, Tram Bui <trambui at u.boisestate.edu> wrote:
>
>> Dear QE Users,
>>        I ran the calculation for a simple 1x1x1 unit cell SiC (zinc blend
>> structure) . The calculated total energy for when ibrav=2 (two atoms per
>> cell) is different from when ibrav=0 (8 atoms per cell). Would you give me
>> some information on why the total energy changes?
>>
>
>
> Dear Tram,
> maybe you did not use 2 sets of k-points that map perfectly from one
> system to the other.
>
> bests
>
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Université Paris 6
> phone: +33 (0)1 44275 084 / skype: paulatz
> www:   http://www-int.impmc.upmc.fr/~paulatto/
> mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
>
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