<s>
SIESTA	B-Application
(	O
Spanish	O
Initiative	O
for	O
Electronic	O
Simulations	O
with	O
Thousands	O
of	O
Atoms	O
)	O
is	O
an	O
original	O
method	O
and	O
its	O
computer	O
program	O
implementation	O
,	O
to	O
efficiently	O
perform	O
electronic	O
structure	O
calculations	O
and	O
ab	O
initio	O
molecular	O
dynamics	O
simulations	O
of	O
molecules	O
and	O
solids	O
.	O
</s>
<s>
SIESTA	B-Application
uses	O
strictly	O
localized	O
basis	O
sets	O
and	O
the	O
implementation	O
of	O
linear-scaling	O
algorithms	O
.	O
</s>
<s>
SIESTA	B-Application
's	O
backronym	O
is	O
the	O
Spanish	O
Initiative	O
for	O
Electronic	O
Simulations	O
with	O
Thousands	O
of	O
Atoms	O
.	O
</s>
<s>
Since	O
13	O
May	O
2016	O
,	O
with	O
the	O
4.0	O
version	O
announcement	O
,	O
SIESTA	B-Application
is	O
released	O
under	O
the	O
terms	O
of	O
the	O
GPL	B-License
open-source	O
license	O
.	O
</s>
<s>
Source	O
packages	O
and	O
access	O
to	O
the	O
development	O
versions	O
can	O
be	O
obtained	O
from	O
the	O
DevOps	O
platform	O
on	O
GitLab	B-Application
.	O
</s>
<s>
The	O
latest	O
version	O
Siesta-4.1.5	O
was	O
released	O
on	O
4	O
February	O
2021	O
.	O
</s>
<s>
SIESTA	B-Application
has	O
these	O
main	O
characteristics	O
:	O
</s>
<s>
It	O
is	O
written	O
in	O
Fortran	B-Application
95	O
and	O
memory	O
is	O
allocated	O
dynamically	O
.	O
</s>
<s>
SIESTA	B-Application
routinely	O
provides	O
:	O
</s>
<s>
Spin	B-General_Concept
polarized	I-General_Concept
calculations	O
(	O
collinear	O
or	O
not	O
)	O
.	O
</s>
<s>
SIESTA	B-Application
main	O
strengths	O
are	O
:	O
</s>
<s>
The	O
use	O
of	O
a	O
linear	O
combination	O
of	O
numerical	O
atomic	O
orbitals	O
makes	O
SIESTA	B-Application
a	O
flexible	O
and	O
efficient	O
DFT	O
code	O
.	O
</s>
<s>
SIESTA	B-Application
is	O
able	O
to	O
produce	O
very	O
fast	O
calculations	O
with	O
small	O
basis	O
sets	O
,	O
allowing	O
the	O
computation	O
of	O
systems	O
with	O
thousands	O
of	O
atoms	O
.	O
</s>
<s>
SIESTA	B-Application
is	O
in	O
continuous	O
development	O
since	O
it	O
was	O
implemented	O
in	O
1996	O
.	O
</s>
<s>
A	O
number	O
of	O
post-processing	O
tools	O
for	O
SIESTA	B-Application
have	O
been	O
developed	O
.	O
</s>
<s>
These	O
programs	O
process	O
SIESTA	B-Application
output	O
or	O
provide	O
additional	O
features	O
.	O
</s>
<s>
Since	O
its	O
implementation	O
,	O
SIESTA	B-Application
has	O
been	O
used	O
by	O
researchers	O
in	O
geosciences	O
,	O
biology	O
,	O
and	O
engineering	O
(	O
extending	O
beyond	O
materials	O
physics	O
and	O
chemistry	O
)	O
and	O
has	O
been	O
applied	O
to	O
a	O
large	O
variety	O
of	O
systems	O
including	O
surfaces	O
,	O
adsorbates	O
,	O
nanotubes	O
,	O
nanoclusters	O
,	O
biological	O
molecules	O
,	O
amorphous	O
semiconductors	O
,	O
ferroelectric	O
films	O
,	O
low-dimensional	O
metals	O
,	O
etc	O
.	O
</s>
