[QE-users] Energy calculation

[Manu Hegde]

Hi Pooja,
I think CaO is a cubic crystal. You can use VESTA to generate a supercell.
It can take .cif file. Play with it. I believe extending lattice
parameter 2X2X2 generate a 36 atom supercell.
HTH
Manu
(McMaster University)

On Sat, Jan 18, 2020 at 12:38 AM Pooja Vyas <poojavyas1251995 at gmail.com>
wrote:

> 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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