[QE-users] Non-smooth tail in potential energy curve for non-metals

[Paolo Giannozzi]

On Wed, Mar 10, 2021 at 5:10 PM Kevin Kayang <kwkayang at crimson.ua.edu>
wrote:


>  ibrav     = 0,
>  celldm(1)= 1.88972687,
>
[...]
>
CELL_PARAMETERS cubic
>    20.000000000   0.0000000000   0.0000000000
>    0.0000000000   20.000000000   0.0000000000
>    0.0000000000   0.0000000000   20.000000000
>

this is an exceptionally obscure way to provide input data. A better one:
ibrav=1, a=20.0

 nosym = .FALSE.
>

why? do you know what it means?

 input_dft = vdw-df2
>

correct syntax: input_dft='vdw-df2'

 one_atom_occupations = .TRUE.,
>

why? do you know what it means?

 starting_magnetization(1) = 1,
>

this means 'all electrons with spin up'. You may use a smaller value to
break the symmetry

 starting_magnetization(2) = 1,
>

this is wrong: there is just one kind of atom, not two, and may lead to
unpredictable behavior.

The energy vs distance curve of a dimer is a simple but tricky problem.
What you observe might be the result of the crossing of two different
curves, one with no spin and the other with spin polarization.

Paolo
-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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