[QE-users] Energy calculation

[Pooja Vyas]

Respected sir/madam,
Referring a paper on calculation of energy with vacancy in CaO, I want to
re-calculate the energy with the same number of atoms used in the paper.
They have 36 atoms in their supercell, 3 x 3 x 2 monk horst pack grid. From
this information, is it possible to know what could be the value of n, in n
x n x n supercell and what could be the initial number of atomic positions
defined?

On Thu, Jan 16, 2020 at 11:58 AM Laurent Pizzagalli <
laurent.pizzagalli at univ-poitiers.fr> wrote:

> Well, maybe because in your first calculation you had two atoms, and 64 in
> the second one.....You should try to see if multiplying -107.10 by 64/2
> improve the comparison....
>
> L.
>
> On 16/01/2020 06:23, Pooja Vyas wrote:
>
> Initially I had run my input script with ecut=100Ry and k-points= 11 11 11
> 1 1 1. At that time my energy was -107.10Ry. During this run, I had
> specified only two atomic positions (Ca: 0 0 0, O: 0.5 0.5 0.5)
> For the same system but with ecut=60Ry and k-points= 3 3 3 1 1 1 the
> calculated energy was -3427.40Ry. During this run, I had specified 64
> atomic positions.
> Why does total energy value vary so much?
>
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