<s>
DP	O
is	O
a	O
free	O
software	B-Application
package	I-Application
for	O
physicists	O
implementing	O
ab	O
initio	O
linear-response	O
TDDFT	O
(	O
time-dependent	O
density	O
functional	O
theory	O
)	O
in	O
frequency-reciprocal	O
space	O
and	O
on	O
a	O
plane	O
wave	O
basis	O
set	O
.	O
</s>
<s>
It	O
allows	O
to	O
calculate	O
both	O
dielectric	O
spectra	O
,	O
such	O
as	O
EELS	B-Application
(	O
electron	O
energy-loss	O
spectroscopy	O
)	O
,	O
IXSS	O
(	O
inelastic	O
X-ray	O
scattering	O
spectroscopy	O
)	O
and	O
CIXS	O
(	O
coherent	O
inelastic	O
X-ray	O
scattering	O
spectroscopy	O
)	O
,	O
and	O
also	O
optical	O
spectra	O
,	O
e.g.	O
</s>
